CN117801128A - Cationic tamarind polysaccharide flocculant powder, preparation method and application thereof - Google Patents

Abstract

The invention relates to cationic tamarind polysaccharide flocculant powder, a preparation method and application thereof, wherein 3-chloro-2-hydroxypropyl trimethyl ammonium chloride (CHPTAC) is used as an etherifying agent, and the cationic tamarind polysaccharide flocculant is obtained by carrying out cationization reaction on tamarind polysaccharide under alkaline conditions. The invention uses natural polysaccharide (tamarind polysaccharide) as a basic raw material, the flocculant preparation process is simple, the secondary pollution risk is reduced, the prepared flocculant is efficient and environment-friendly, the prepared flocculant is solid powder, the storage is convenient, and the flocculation effect on kaolin simulated wastewater is obvious.

Description

Cationic tamarind polysaccharide flocculant powder, preparation method and application thereof

Technical Field

The invention relates to the field of biomass fine chemicals, and in particular to a cationic tamarind polysaccharide flocculant powder, a preparation method and its application.

Background technique

Untimely and non-compliant treatment of papermaking wastewater, food and drug production wastewater, textile wastewater, etc. leads to deterioration of water quality. How to provide safe, reliable and clean water is a huge challenge for us.

Over the past few decades, adsorption, oxidation, biotechnology, and flocculation have been the main methods for wastewater treatment. Among them, flocculation refers to adding appropriate flocculants to make suspended particles in water or liquid aggregate and become larger, or form flocs, thereby accelerating the aggregation and sinking of particles to achieve the purpose of solid-liquid separation. Due to its simple operation and low cost, it has gradually become a mainstream sewage treatment method. Obviously, in the flocculation treatment process, the correct selection of flocculant is the key to convenient, fast and qualified sewage treatment. The appropriate flocculant can achieve twice the result with half the effort. The flocculants commonly used in water treatment are mainly divided into two categories: organic flocculants and inorganic flocculants. The main organic flocculants are poly(diallyldimethylammonium chloride) and polyacrylic acid, and the main inorganic flocculants are ferrous sulfate, polyaluminum chloride and alum. However, the shortcomings of these two types of flocculants are also very obvious, that is, they can easily lead to "secondary pollution" and the emergence of new environmental problems, and the monomers released during the water treatment process may cause harmful effects if they enter the food chain and are ingested by the human body. Increased risk of cancer. Therefore, how to develop safe and efficient flocculants is still an urgent problem to be solved.

In recent years, research on polysaccharide flocculants has become more and more common. Polysaccharides are natural macromolecular carbohydrates composed of monosaccharides. They come from a wide range of sources and can be extracted from higher plants, animals, microorganisms, lichens and seaweeds. They have high Shear stability makes them more versatile and biosafe.

Tamarind polysaccharide (TSP) is derived from tamarind seeds. It is a xyloglucan composed of galactose, xylose and glucose in a ratio of about 1:2:3. It is composed of β-1,4-glucan. The main chain is partially replaced by xylose at the O-6 position, and part of the xylose is replaced by galactose at the O-2 position. It has good heat resistance, salt resistance, acid resistance and freezing resistance. Due to its non-toxicity and biocompatibility, TSP is often used as drug encapsulation and sustained-release packaging materials. In addition, TSP can also be used as an adhesive and thickener in toothpaste, detergents, and tobacco industries, and as a Sizing materials for textile printing. However, TSP is still rarely used in wastewater treatment. As an economical, non-toxic, easily available, and biodegradable biomacromolecule material, TSP is also an excellent candidate for manufacturing bioflocculants. Therefore, the development of TSP-based flocculants has great prospects and practical significance.

Patent application CN103012613A discloses a cationic tamarind polysaccharide and its preparation method. The tamarind polysaccharide is dispersed in an appropriate amount of organic solvent aqueous solution, an alkali is added to fully carry out the filamentation reaction, and then a cationic reagent is added to fully mix and adsorb, filter, and the filter cake is The cationic tamarind polysaccharide gum is obtained by carrying out etherification reaction while drying at a certain temperature for a certain period of time. However, the steps of this method are complicated and consume a lot of energy.

Patent application CN105384874A discloses a water-in-water emulsion type cationic polysaccharide bioflocculant and its preparation method. Autopolymers or copolymers of several unsaturated cationic monomers are used as stabilizers, and nonionic polysaccharide bioflocculants are used as auxiliary stabilizers. The agent uses an aqueous solution of inorganic salt as the continuous phase, and through certain process control, it undergoes free radical polymerization in the internal phase aqueous solution to form a stably dispersed cationic polysaccharide bioflocculant emulsion containing microscopic polymer particles. However, when flocculants exist in the form of emulsions, stability issues need to be considered, and the liquid state is difficult to transport and preserve.

Contents of the invention

The purpose of the present invention is to provide a cationic tamarind polysaccharide flocculant powder, a preparation method and its application in order to overcome the above-mentioned defects in the prior art that the emulsion flocculant is unstable and difficult to transport.

The object of the present invention can be achieved through the following technical solutions:

One aspect of the present invention provides a cationic tamarind polysaccharide flocculant powder. Using tamarind polysaccharide solution as raw material, the simplified molecular structure formula of the prepared cationic polysaccharide flocculant is:

Among them, Dx is tamarind polysaccharide, and its simplified structural formula is:

The second aspect of the present invention provides a method for preparing the cationic tamarind polysaccharide flocculant powder, comprising the following steps:

S1: Tamarind polysaccharide was dissolved in deionized water to prepare a 2-3% w/v tamarind polysaccharide solution;

S2: Alkalization treatment: adjust the pH of the tamarind polysaccharide solution in step S1 to 9 and maintain it for 30 minutes;

S3: Cationization reaction: Add the etherifying agent 3-chloro-2-hydroxypropyltrimethylammonium chloride (CHPTAC) to the tamarind polysaccharide solution obtained in step S2, heat and stir, and maintain the pH of the solution system = 9 -9.5;

S4: Stopping the cationization reaction: adjusting the pH value of the tamarind polysaccharide solution obtained in step S3 to 6.5-7, stopping the cationization reaction, and cooling to room temperature;

S5: Precipitation: Add absolute ethanol to the solution obtained in step S4 until the ethanol volume fraction is 80%, allow alcohol precipitation overnight, and centrifuge to obtain tamarind polysaccharide precipitation;

S6: Dehydrate the tamarind polysaccharide precipitation obtained in step S5 with isopropyl alcohol, dry and grind to obtain cationic tamarind polysaccharide flocculant powder.

Preferably, the preparation method includes the following steps:

S1: Dissolve tamarind polysaccharide in deionized water to prepare a 2% w/v tamarind polysaccharide solution;

S2: Alkalization treatment: adjust the pH of the tamarind polysaccharide solution described in step S1 to 9, and maintain it for 30 minutes;

S3: Cationization reaction: Add the etherifying agent 3-chloro-2-hydroxypropyltrimethylammonium chloride to the tamarind polysaccharide solution obtained in step S2, heat and stir, and maintain the pH of the solution system = 9-9.2;

S4: Stop the cationization reaction: Adjust the pH value of the tamarind polysaccharide solution obtained in step S3 to 6.5-7, stop the cationization reaction, and cool to room temperature;

S5: Precipitation: Add absolute ethanol to the solution obtained in step S4 until the ethanol volume fraction is 80%, allow alcohol precipitation overnight, and centrifuge to obtain tamarind polysaccharide precipitation;

S6: Dehydrate the tamarind polysaccharide precipitation obtained in step S5 with isopropyl alcohol, dry and grind to obtain cationic tamarind polysaccharide flocculant powder.

More preferably, the preparation method includes the following steps:

S1: Weigh 1.0g of tamarind polysaccharide into 50 mL of deionized water to prepare a 2% w/v tamarind polysaccharide solution;

S2: Alkalization treatment: Use 1M sodium hydroxide solution to adjust the pH of the tamarind polysaccharide solution in step S1 to 9 and maintain it for 30 minutes;

S3: Cationization reaction: Add the etherifying agent 3-chloro-2-hydroxypropyltrimethylammonium chloride to the tamarind polysaccharide solution obtained in step S2, heat and stir, and maintain the pH of the solution system = 9;

S4: Stop the cationization reaction: Use 1M hydrochloric acid solution to adjust the pH value of the tamarind polysaccharide solution obtained in step S3 to 6.5-7, stop the cationization reaction, and cool to room temperature;

S5: Precipitation: Add absolute ethanol to the solution obtained in step S4 until the ethanol volume fraction is 80%, allow alcohol precipitation overnight, and centrifuge to obtain tamarind polysaccharide precipitation;

S6: Dehydrate the tamarind polysaccharide precipitation obtained in step S5 with isopropyl alcohol, dry and grind to obtain a cationic tamarind polysaccharide flocculant.

Further, the molar ratio of anhydrous glucose in the tamarind polysaccharide described in step S3 to the etherifying agent 3-chloro-2-hydroxypropyltrimethylammonium chloride is 1:1-9.

Preferably, the molar ratio of anhydrous glucose in the tamarind polysaccharide described in step S3 to the etherifying agent 3-chloro-2-hydroxypropyltrimethylammonium chloride is 1:1, or 1:5, or 1:9.

More preferably, the molar ratio of anhydrous glucose and etherifying agent 3-chloro-2-hydroxypropyltrimethylammonium chloride in the tamarind polysaccharide described in step S3 is 1:9.

Further, the heating temperature in step S3 is 45-55°C, and the heating time is 5 hours.

Preferably, the heating temperature in step S3 is 50°C.

Furthermore, the centrifugal speed in step S5 is 3500-4500 r/min.

Preferably, the centrifugal speed in step S5 is 4000 r/min.

Further, the drying temperature in step S6 is 55-65°C, and the drying time is 2.5-3.5h.

Preferably, the drying temperature in step S6 is 60°C, and the drying time is 3.0 h.

The third aspect of the present invention provides the cationic tamarind polysaccharide flocculant powder for the treatment of kaolin simulated sewage, and the pH of the kaolin solution is 4 or 7.

Compared with the existing technology, the present invention has the following advantages:

(1) A method for preparing a cationic tamarind polysaccharide flocculant powder provided by the invention, using 3-chloro-2-hydroxypropyltrimethylammonium chloride as the etherifying agent, and tamarind polysaccharide under alkaline conditions. Carry out cationization reaction to obtain cationic tamarind polysaccharide flocculant powder. The present invention applies tamarind polysaccharide to sewage treatment, broadens the application scope of tamarind polysaccharide, and provides a new product that is helpful for sewage treatment.

(2) The preparation method of a cationic tamarind polysaccharide flocculant powder provided by the invention has simple steps, effectively reduces production costs and reduces energy consumption. At the same time, the prepared flocculant is in the form of solid powder, which is easy to store and has a significant flocculation effect on kaolin simulated wastewater. It can be considered a simple and effective preparation technology for cationic tamarind polysaccharide flocculant.

Description of drawings

FIG1 is a SEM scan of tamarind polysaccharide in Example 1;

FIG2 is a SEM scan of the cationic tamarind polysaccharide flocculant powder prepared in Example 1;

Figure 3 is an SEM scanning image of the cationic tamarind polysaccharide flocculant powder prepared in Example 2;

FIG4 is a SEM scan of the cationic tamarind polysaccharide flocculant powder prepared in Example 3;

Figure 5 is the HPSEC-MALLS diagram of TSP and the cationic tamarind polysaccharide flocculant powder prepared in Examples 1-3 (a: TSP; b: Example 1; c: Example 2; d: Example 3);

Figure 6 is a Zeta potential diagram of TSP and the cationic tamarind polysaccharide flocculant powder prepared in Examples 1-3;

Figure 7 is the Fourier transform infrared spectrum of TSP and the cationic tamarind polysaccharide flocculant powder prepared in Examples 1-3;

Figure 8 is the nuclear magnetic resonance spectrum of TSP and the cationic tamarind polysaccharide flocculant powder prepared in Example 3;

Figure 9 is the thermodynamic characterization of TSP and cationic tamarind polysaccharide flocculant powder prepared in Examples 1-3;

Figure 10 shows the solubility (a) and apparent viscosity curve (b) of TSP and cationic tamarind polysaccharide flocculant powder prepared in Examples 1-3;

FIG. 11 is a graph showing the flocculation performance of the cationic tamarind polysaccharide flocculant powders prepared by TSP and Examples 1-3.

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

If there is no specific description, various raw materials of the present invention can be purchased commercially, or can be prepared according to conventional methods in the art. The cationic tamarind polysaccharide flocculant powder prepared in the following Examples 1, 2 and 3 will be referred to as "Example 1", "Example 2" and "Example 3" for short.

Example 1

This embodiment provides a cationic tamarind polysaccharide flocculant powder, which is prepared by the following method. The steps are as follows:

S1: Weigh 1.0 g of tamarind polysaccharide in 50 mL of deionized water to prepare a 2% w/v tamarind polysaccharide solution;

S2: Alkalization treatment: Use 1M sodium hydroxide solution to adjust the pH of the tamarind polysaccharide solution described in step S1 to 9, and maintain it for 30 minutes;

S3: Cationization reaction: accurately weigh 1.57 mL of 3-chloro-2-hydroxypropyltrimethylammonium chloride (CHPTAC) (65 wt% aqueous solution) and add it to the tamarind polysaccharide solution obtained in step S2 (n(TSP):n(CHPTAC)=1:3), heat and stir at 50°C for 5 h, and maintain the solution system pH=9;

S4: Stop the cationization reaction: Use 1M hydrochloric acid solution to adjust the pH value of the tamarind polysaccharide solution obtained in step S3 to 6.5-7, stop the cationization reaction, and cool to room temperature;

S5: Precipitation: Add absolute ethanol to the solution obtained in step S4 until the ethanol volume fraction is 80%, allow alcohol precipitation overnight, and centrifuge at 4000 r/min to obtain tamarind polysaccharide precipitation;

S6: Dehydrate the tamarind polysaccharide precipitation obtained in step S5 with isopropyl alcohol, dry at 60°C for 3 hours, dry and grind to obtain cationic tamarind polysaccharide flocculant powder.

Example 2

The preparation method of this embodiment is the same as that of Example 1, except that the addition amount of 3-chloro-2-hydroxypropyltrimethylammonium chloride (CHPTAC) (65wt% aqueous solution) in step S3 is 7.80mL (n(TSP): n(CHPTAC)=1:6).

Example 3

The preparation method of this embodiment is the same as that of Example 1, except that the addition amount of 3-chloro-2-hydroxypropyltrimethylammonium chloride (CHPTAC) (65wt% aqueous solution) in step S3 is 14.05mL (n(TSP): n(CHPTAC)=1:9).

As shown in Figure 1-4, a scanning electron microscope was used to observe the microstructure of tamarind polysaccharide and the prepared cationic tamarind polysaccharide flocculant powder. The tamarind polysaccharide showed a relatively smooth surface. As the degree of substitution gradually increased, CTSPs The appearance changes and the surface becomes uneven. The reason for this destruction of particle integrity is attributed to the loss of TSP structure and the breakage of chemical bonds under the dual environment of strong alkalinity and heat treatment.

An elemental analyzer was used to detect the elemental composition of tamarind polysaccharide before and after modification. The degree of substitution was calculated according to formula (1).

Wherein, 162 is the molecular weight of AGU, 151.6 is the molecular weight of the substituent, and N is the nitrogen content measured by an elemental analyzer, expressed as a percentage.

Table 1 Substitution degree and molecular parameters of tamarind polysaccharide before and after modification

The elemental analysis results of TSP and Examples 1-3 are shown in Table 1. The nitrogen content in TSP is 0, and the prepared cationic tamarind polysaccharide flocculant powder contains a high proportion of nitrogen, proving that quaternary ammonium groups have been successfully incorporated into TSP. The DS of the cationic tamarind polysaccharide flocculant powder prepared in Examples 1-3 was tested. As the addition amount of CHPTAC increased, the proportion of nitrogen increased. This effect was accompanied by an increase in the degree of substitution. Example 1 was calculated. , the DS of the cationic tamarind polysaccharide flocculant powder prepared in Example 2 and Example 3 are 0.143, 0.197 and 0.346 respectively.

HPSEC-MALLS was used to determine the molecular parameters and conformational changes of TSP and the prepared cationic tamarind polysaccharide flocculant powder, as shown in Figure 5 and Table 1. The single peak shown in the figure indicates that TSP and the prepared cationic tamarind polysaccharide flocculant powder are uniform in molecular weight distribution, but a small shoulder peak is found in TSP, which is due to the smaller aggregates present in TSP. After cationization, no small shoulder peaks were found in the prepared cationic tamarind polysaccharide flocculant powder, which was due to the degradation of small aggregates caused by alkaline reaction conditions. This can also be seen from the change in its molecular weight, as shown in Table 1. In this study, the weight average molecular weight (Mw) of TSP is 9.06×10 ⁵ g/mol. The Mw of the cationic tamarind polysaccharide flocculant powder prepared in Examples 1-3 are 7.61×10 ⁵ g/mol and 7.30×10 ⁵ respectively. g/mol and 6.81×10 ⁵ g/mol, both are lower than TSP, indicating that the prepared cationic tamarind polysaccharide flocculant powder has different degrees of degradation during the preparation process, but the Mw is still of the same order of magnitude, and this difference can be ignored .

As shown in Figure 6, the cationic tamarind polysaccharide flocculant was tested using a Zeta potential meter. Zeta potential not only characterizes the charge type of particles, but can also further determine the results of modification. The Zeta potential of TSP is -3.78mV. As the substitution degree continues to increase, the Zeta potential of the prepared cationic tamarind polysaccharide flocculant powder also gradually increases. Especially when n(TSP):n(CHPTAC)=1:9 (Example 3), the Zeta potential of the prepared cationic tamarind polysaccharide flocculant powder reaches 12.00mV. This clearly shows that the prepared cationic tamarind polysaccharide flocculant powder behaves as a polycationic polyelectrolyte by introducing positively charged quaternary ammonium salt groups on the TSP chain.

As shown in Figure 7, the cationic tamarind polysaccharide flocculant was tested using a Fourier transform infrared spectrometer. A broad and strong absorption peak appeared at around 3341 cm ^-1. This was due to the OH pull of the glucan backbone of the TSP network. The weak absorption peak near 2910 cm ^-1 is caused by the asymmetric CH stretching vibration of methylene groups such as -CH ₂ groups. The above two absorption peaks are considered to be the characteristic areas of the infrared spectrum of polysaccharide polymers. The zone formed between 1200 and 800 cm ^-1 is considered to be the "fingerprint" zone of polysaccharides, which is mainly caused by the vibration of some glycosidic bonds, sugar rings, etc. The most obvious difference between TSP and the prepared cationic tamarind polysaccharide flocculant powder is at 1479cm ^-1 . This peak corresponds to CN stretching, while TSP does not have this absorption peak, proving that (CH ₃ ) ₃ N ⁺ is on the TSP chain. Successfully attached.

The 1H NMR spectra of TSP and the cationic tamarind polysaccharide flocculant powder prepared in Example 3 are shown in Figure 8. The sample was first dissolved with D ₂ O and then lyophilized, repeated three times to completely convert active -OH into -OD. The samples were then dissolved in 1 mL D ₂ O and subjected to ¹ H and ¹³ C NMR analysis using a Bruker 600 NMR spectrometer. The ¹ H NMR spectra of TSP and the cationic tamarind polysaccharide flocculant powder prepared in Example 3 are shown in Figure 8(a). In the ¹ H NMR spectrum, there are three main heterogeneous proton signals in the heterogeneous proton region, which are 5.12ppm, 4.91ppm and 4.51ppm respectively. Among them, the signals at 5.12ppm and 4.91ppm are →2)-α-Xylp-(1→ residue and α-D-Xylp terminal respectively, while the signal at 4.51ppm represents T-β-Galp, →4) respectively. -α-Glcp-(1→ and →4,6)-α-Glcp-(1→. Compared with TSP, the spectrum of CTSP shows a difference in the 3.20ppm region, and this signal represents the -N ⁺ (CH ₃ ) ₃ group. Figure 8(b) shows the ¹³ C NMR spectra of TSP and the cationic tamarind polysaccharide flocculant powder prepared in Example 3. Compared with the spectrum of TSP, the cationic tamarind polysaccharide flocculation prepared in Example 3 Some new signals appeared in the agent powder, which represented Cδ(CH ₃ ) ₃ N ⁺ , Cβ(CHOH) and Cγ(CH ₂ -N ⁺ ) at 54.5, 65.6 and 68.3 ppm respectively.

Thermodynamic experiments were carried out using a synchronous thermal analyzer. The samples were placed in a special alumina pot and heated from 30°C to 600°C at a rate of 10°C/min under a N2 atmosphere. At the same time, an empty special alumina pot was used as a reference. All experiments were repeated three times, and thermogravimetric (TG), derivative thermogravimetric (DTG) and differential scanning calorimetry (DSC) data were obtained simultaneously. The thermal properties of the cationic tamarind polysaccharide flocculant powders prepared by TSP and Examples 1-3 are shown in Figure 9. The pyrolysis behavior of polysaccharides consists of three different degradation stages. In the first stage (30-180°C), the cationic tamarind polysaccharide flocculant powders prepared by TSP and Examples 1-3 both showed a small amount of moisture loss, which was mainly due to the volatilization of free water and bound water in the polysaccharide. The second stage is concentrated at 240-360°C, which is the main stage of polysaccharide decomposition. In this stage, the weight loss of the cationic tamarind polysaccharide flocculant powder prepared by TSP and Examples 1, 2, and 3 is 68.95%, 54.98%, 56.26%, and 51.68%, respectively, which is due to the dissociation and devolatization of glycosides. The higher temperatures (Tm) (277.59°C, 294.89°C, and 275.48°C) corresponding to the maximum degradation rate in the DTC curve of the cationic tamarind polysaccharide flocculant powder prepared by Examples 1-3 are significantly lower than 334.11°C of TSP, indicating that the main pyrolysis behavior of TSP is related to its structure. The thermal stability of polysaccharides decreases after cationization, which may be due to the chemical degradation and cleavage of hydroxyl bonds during the derivatization process. When the temperature is further increased to 600°C, the polysaccharide is carbonized into ash, producing carbon dioxide, and the third stage of weight loss occurs. The residual mass of the cationic tamarind polysaccharide flocculant powder prepared in Examples 1-3 at the highest temperature is higher than that of TSP. This is because the chlorine element is introduced in the cationization reaction, which makes the cationic tamarind polysaccharide flocculant powder prepared in Examples 1-3 have a higher residual mass (24.04%, 26.58%, 31.78%, w/w) at the highest temperature.

The DSC curves of TSP and the cationic tamarind polysaccharide flocculant powders prepared in Examples 1-3 are also given in Figure 9. It is noteworthy that the enthalpy values of the dehydration temperature and the pyrolysis temperature of the polysaccharide are both reduced. Since the decomposition exotherm is related to the breaking of intermolecular and intramolecular interactions and the decomposition of the polysaccharide, it can be concluded that cationization destroys the hydrogen bonds of the TSP chains, which is consistent with the results of TGA. Despite the reduction in decomposition temperature, the thermal stability above 200°C is still sufficient for most potential applications of these cationic products.

The effect of different degrees of cationization on the solubility of TSP was evaluated, as shown in Figure 10(a). The solubility of TSP increases as the degree of substitution increases. For example, when the degree of substitution increases from 0 (TSP) to 0.346 (cationic tamarind polysaccharide flocculant powder prepared in Example 3), the solubility of TSP increases from 34% to 64%. Obviously, cationization plays a positive role in the water solubility of TSP, and in this study, the decrease in molecular weight of the prepared cationic tamarind polysaccharide flocculant powder as the degree of substitution increases is a factor in the increase in its solubility.

The flow curves of the cationic tamarind polysaccharide flocculant powders prepared by TSP and Example 1-3 are shown in Figure 10(b). The apparent viscosity of the cationic tamarind polysaccharide flocculant powders prepared by TSP and Example 1-3 remains unchanged in the low shear rate region, and decreases with the increase of shear rate in the high shear rate region. The apparent viscosity of the cationic tamarind polysaccharide flocculant powders prepared by Example 1-3 is lower than that of TSP. Since the high-viscosity TSP has a higher molecular weight, the difference in apparent viscosity between TSP and the cationic tamarind polysaccharide flocculant powders prepared by Example 1-3 may be related to structural characteristics. This may be related to the increase in the hydrophilicity of the polymer and the decrease in molecular weight caused by the degradation of the polysaccharide under alkaline conditions.

The power law model was used to fit the rheological data, and the results are shown in Table 2. The pseudoplastic flow behavior of TSP is more typical than that of the cationic tamarind polysaccharide flocculant powder prepared in Examples 1-3. In addition, the K values of TSP and cationic tamarind polysaccharide flocculant powder prepared in Examples 1, 2, and 3 are 0.28, 0.19, 0.09, and 0.06 respectively, which confirms the high viscosity of the former.

Table 2 Parameters of 1% (w/v) TSP and cationic tamarind polysaccharide flocculant powder prepared in Examples 1-3

Using 1.0g/L kaolin solution as a simulated sewage sample, the flocculation performance of cationic tamarind polysaccharide flocculant powder under pH=7 and pH=4 conditions was studied. At pH=7, with the gradual increase in the dosage of cationic tamarind polysaccharide flocculant powder, the light transmittance of kaolin simulated water samples showed an increasing trend, and showed a downward trend after reaching a certain dosage. The surface of kaolin particles is negatively charged, and the particles repel each other and are suspended, making the solution turbid when dissolved in water. Therefore, when the positively charged cationic tamarind polysaccharide flocculant powder is added to the kaolin suspension, the cationic tamarind polysaccharide flocculant powder will be adsorbed by the kaolin particles, thereby neutralizing the negative charge of the kaolin itself and weakening the repulsion between particles, thus Aggregation and sedimentation, but when the dosage is greater than the optimal dosage, excessive positive charges are adsorbed on the suspended matter, and the flocculation effect tends to decrease due to electrostatic repulsion. The results in Figure 11(a) show that the cationic tamarind polysaccharide flocculant powder prepared in Example 2 and Example 3 has good flocculation ability for kaolin simulated water samples. Although the cationic tamarind polysaccharide powder prepared in Example 2 and Example 3 The flocculation effect of flocculant powder is slightly lower than that of cationic guar gum (CGG), but the transmittance can still reach more than 85%. The flocculation effect of the cationic tamarind polysaccharide flocculant powder prepared in Example 1 is lower than that of the cationic tamarind polysaccharide flocculant powder prepared in Example 2 and Example 3. This phenomenon is consistent with the cationic tamarind polysaccharide flocculant powder prepared in Example 1. The degree of substitution is lower than that of the cationic tamarind polysaccharide flocculant powder prepared in Examples 2 and 3. Compared with the cationic tamarind polysaccharide flocculant powder prepared in Example 2, the flocculation effect of the cationic tamarind polysaccharide flocculant powder prepared in Example 3 is not significantly improved, which is due to the positional blocking effect.

Figure 11(b~d) shows the test results of the flocculation performance of the cationic tamarind polysaccharide flocculant powder prepared in Examples 1-3 on kaolin simulated water samples at pH=4. Obviously, the lower the pH, the less flocculant is needed to achieve the same flocculation effect. This is because the lower the pH, the more positive charges in the water sample system, which can neutralize some of the negatively charged kaolin particles, thus achieving the same flocculation. The dosage of the cationic tamarind polysaccharide flocculant powder prepared in Examples 1-3 required for the effect is relatively low. The flocculation effect is also reflected in the changes in Zeta potential of the water sample system. When pH=4, the pH value of kaolin simulated water sample is -14.8mV. As the cationic tamarind polysaccharide flocculant powder prepared in Examples 1-3 is gradually added, the Zeta potential of the water sample system gradually increases. When the transmittance reaches its maximum value, the zeta potential is close to 0mV.

Claims (10)

1. The cationic tamarind polysaccharide flocculant powder is characterized in that a tamarind polysaccharide solution is used as a raw material, and the molecular structure of the prepared cationic tamarind polysaccharide flocculant powder is as follows:

wherein Dx is tamarind polysaccharide, and the structural formula is as follows:

2. a process for the preparation of the cationic tamarind seed polysaccharide flocculant powder of claim 1, comprising the steps of:

s1: dissolving tamarind polysaccharide in deionized water to prepare 2-3% w/v tamarind polysaccharide solution;

s2: alkalizing: regulating the pH value of the tamarind polysaccharide solution in the step S1 to 9, and keeping for 30min;

s3: cationization reaction: adding an etherifying agent 3-chloro-2-hydroxypropyl trimethyl ammonium chloride into the tamarind polysaccharide solution obtained in the step S2, heating and stirring, and maintaining the pH value of a solution system to be 9-9.5;

s4: stop the cationization reaction: regulating the pH value of the tamarind polysaccharide solution obtained in the step S3 to 6.5-7, stopping the cationization reaction, and cooling to room temperature;

s5: precipitation: adding absolute ethyl alcohol into the solution obtained in the step S4 until the volume fraction of the absolute ethyl alcohol is 80%, precipitating the solution by alcohol overnight, and centrifuging to obtain a tamarind polysaccharide precipitate;

s6: and (3) dehydrating the tamarind polysaccharide precipitate obtained in the step (S5) by isopropanol, and drying and grinding to obtain cationic tamarind polysaccharide flocculant powder.

3. A process for the preparation of a cationic tamarind seed polysaccharide flocculant powder according to claim 2, comprising the steps of:

s1: dissolving tamarind polysaccharide in deionized water to prepare 2% w/v tamarind polysaccharide solution;

s2: alkalizing: regulating the pH value of the tamarind polysaccharide solution in the step S1 to 9, and keeping for 30min;

s3: cationization reaction: adding an etherifying agent 3-chloro-2-hydroxypropyl trimethyl ammonium chloride into the tamarind polysaccharide solution obtained in the step S2, heating and stirring, and maintaining the pH value of a solution system to be 9-9.2;

s4: stop the cationization reaction: regulating the pH value of the tamarind polysaccharide solution obtained in the step S3 to 6.5-7, stopping the cationization reaction, and cooling to room temperature;

s5: precipitation: adding absolute ethyl alcohol into the solution obtained in the step S4 until the volume fraction of the absolute ethyl alcohol is 80%, precipitating the solution by alcohol overnight, and centrifuging to obtain a tamarind polysaccharide precipitate;

s6: and (3) dehydrating the tamarind polysaccharide precipitate obtained in the step (S5) by isopropanol, and drying and grinding to obtain cationic tamarind polysaccharide flocculant powder.

4. A process for the preparation of a cationic tamarind seed polysaccharide flocculant powder according to claim 3, comprising the steps of:

s1: 1.0g of tamarind polysaccharide is weighed in 50mL of deionized water to prepare 2% w/v tamarind polysaccharide solution;

s2: alkalizing: adjusting the pH of the tamarind seed polysaccharide solution of step S1 to 9 with 1M sodium hydroxide solution and maintaining for 30min;

s3: cationization reaction: adding an etherifying agent 3-chloro-2-hydroxypropyl trimethyl ammonium chloride into the tamarind polysaccharide solution obtained in the step S2, heating and stirring, and maintaining the pH=9 of the solution system;

s4: stop the cationization reaction: regulating the pH value of the tamarind polysaccharide solution obtained in the step S3 to 6.5-7 by using 1M hydrochloric acid solution, stopping the cationization reaction, and cooling to room temperature;

s5: precipitation: adding absolute ethyl alcohol into the solution obtained in the step S4 until the volume fraction of the absolute ethyl alcohol is 80%, precipitating the solution by alcohol overnight, and centrifuging to obtain a tamarind polysaccharide precipitate;

s6: and (3) dehydrating the tamarind polysaccharide precipitate obtained in the step (S5) by isopropanol, and drying and grinding to obtain cationic tamarind polysaccharide flocculant powder.

5. The method for preparing the cationic tamarind seed polysaccharide flocculant powder according to claim 4, wherein the molar ratio of anhydrous glucose in the tamarind seed polysaccharide to the etherifying agent 3-chloro-2-hydroxypropyl trimethylammonium chloride in step S3 is 1:1-9.

6. The method for preparing the cationic tamarind seed polysaccharide flocculant powder according to claim 4, wherein the molar ratio of anhydrous glucose in the tamarind seed polysaccharide to the etherifying agent 3-chloro-2-hydroxypropyl trimethylammonium chloride in step S3 is 1:1, or 1:5, or 1:9.

7. the method for preparing a cationic tamarind seed polysaccharide flocculant powder according to claim 4, wherein the heating temperature in step S3 is 45-55 ℃ and the heating time is 5 hours.

8. The method for preparing a cationic tamarind seed polysaccharide flocculant powder according to claim 4, wherein the rotational speed of said centrifugation in step S5 is 3500-4500r/min.

9. The method for preparing a cationic tamarind seed polysaccharide flocculant powder according to claim 4, wherein the drying temperature in step S6 is 55-65 ℃ and the drying time is 2.5-3.5h.

10. Use of a cationic tamarind seed polysaccharide flocculant powder according to claim 1 for the treatment of kaolin simulated sewage, said kaolin solution having a pH of 4 or 7.