Natural polysaccharide flocculants, with their green, safe, and renewable properties, represent a transition of sustainable development in the field of water treatment. However, they are confronted with challenges regarding their flocculation efficiency and feasibility under complex environmental factors. In this study, a ternary anionic flocculant of xanthan gum-sodium p-styrenesulfonate-sodium alginate (XSS) was synthesized by means of hydrothermal polymerization. The optimal synthesis conditions were determined with monomer ratio of 1:2:1, initiator dosage of 1.0 wt%, reaction time of 5 h, and reaction temperature of 65 degrees C based on the flocculation efficiency of cationic dye methylene blue (MB). At an XSS concentration of 200 mg/L, the maximum removal efficiency toward 100 mg/L MB simulated wastewater reached 82.1%, due to its rich functional groups and negative charge. Moreover, it showed superior flocculation performance at a pH range of 4-10, temperatures between 10 degrees C and 40 degrees C, and with various inorganic salts of Na+, Ca2 +, and Fe3 +. Correlation analysis between the maximum removal efficiency and initial dye concentration indicates that charge neutralization is the dominant flocculation mechanism. The operating expense was calculated about 72% of that of an anionic polyacrylamide with comparable decolorization efficiency. The successful preparation of XSS provides a new approach for the utilization of natural polysaccharides for wastewater treatment in terms of environmental safety and high efficiency.

The chemical modification of natural polysaccharides is an effective way to synthesise high-performance adsorbents to deal with complex wastewater. Herein, by means of graft copolymerization of sodium alginate and sodium p-styrenesulfonate combined with thermally induced phase separation technology, a foam with both abundant negative charge sites and a 3D porous and fibrous structure was constructed, realizing efficient adsorption of cationic dyes. The adsorption capacity for crystal violet reached 807.1 mg/g, 2.55 times greater than that of the pure sodium alginate foam. The efficiency remained over 90% after 5 cycles. Moreover, the fibrous foams exhibited superior adsorption performance under alkaline conditions. The adsorption process was well described by the pseudo-second-order kinetic equation and conformed to the Langmuir isotherm, suggesting that the uptake was primarily governed by chemical interactions. The thermodynamic results demonstrated that the dye adsorption was spontaneous. This work introduces a valuable approach for enhancing the adsorption performance of natural polysaccharide-based materials, offering great potential in the treatment of dye-contaminated wastewater.

In the face of complex dye wastewater, the development of amphoteric adsorbents for effective removal is imperative. Herein, millimetre-sized amphoteric chitosan/sodium alginate hollow vesicles were successfully prepared via a facile hydrothermal stirring method. The abundant functional groups, uniformly distributed micropores, and inner cavities contribute to enhance the adsorption capacity towards various types of charged dyes, including methylene blue (144.8 mg/g), acid blue-113 (654.9 mg/g), and methyl orange (400.3 mg/g). The vesicles worked well in the pH range of 3-11 and salt concentration up to 100 mmol/L, and remained >92 % of the original adsorption capacity after four cycles. The adsorption is a thermodynamic spontaneous process and the adsorption mechanism is monolayer chemisorption. Importantly, the vesicles possess semi-permeable membrane properties and excellent selectivity, making them favourable for complex wastewater treatment. The environment-friendly and high-performance amphoteric vesicles made from natural marine polysaccharides offer new possibilities for the development of effective absorbents.

Dye wastewater presents a growing threat to both the natural environment and human health, necessitating the development of efficient, cost-effective, and eco-friendly flocculants for its treatment. In response to this challenge, this study successfully prepared a carboxymethyl cellulose-acrylamide-sodium alginate (CAS) anionic terpolymer via a microwave-assisted copolymerization method. Through the flocculation performance towards a simulated dye wastewater containing 100 mg/L of the cationic dye crystal violet, the optimal synthesis process was determined. Results indicated that the optimal CAS concentration of 30 mg/L achieved a removal rate of up to 93.7% for the dye solution of 100 mg/L. The flocculation mechanism of the CAS polymer is primarily based on charge neutralization, with additional effects from bridging and net trapping. This mechanism allows for excellent flocculation performance across wide ranges of dye concentration, pH, and ambient temperature. Furthermore, the cost of CAS is nearly equivalent to that of commercially available polyacrylamide, yet it offers a significant reduction in operating costs, accounting for only one-fifth of the cost required for polyacrylamide to remove the same amount of dye. The prepared CAS copolymer offers the advantages of abundant sourcing, low cost, eco-friendliness, and high performance, making it a highly competitive candidate for practical wastewater treatment.

To improve the selective adsorption of the target pollutant, this study successfully synthesized chitosan/carboxymethyl cellulose molecularly imprinted hollow vesicles (CS/CMC-MIV) for selective adsorption of acid blue-113 (AB-113). The vesicles were obtained by mixing the carboxymethyl cellulose solution with the chitosan/AB-113 mixture in sequential fast and slow stirring. Benefiting from the molecular imprinting technique, the maximum adsorption capacity of AB-113 by CS/CMC-MIV was 972.7 mg/g, which was 84.8

Doped polyaniline is a widely used conductive material and could be used for adsorption based on the electrostatic neutralization effect through the protonation of the imine group. However, the adsorption effect and mechanism towards cationic and anionic pollutants are not clear. Herein, the conductive sulfonic acid doped polyaniline was introduced into alginate/chitosan amphoteric composite foams prepared with a thermal induced phase separation technique. The composite foams were characterized in terms of scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and electrochemical impedance. The composite foam exhibited rich pores and fibrous matrix due to the unique ternary solvent system. The polyaniline was well-distributed and enhanced the cationic dye adsorption ability, contrary to that of anionic dye. Compared with pure alginate/chitosan composite foam, the adsorption capacity of methylene blue was increased by 91.1%, and that of acid blue-113 was reduced by 49.2%. The adsorption rate of the two dyes was both increased. Polyaniline addition enhances the ionic mobility rate and accelerates the movement of dye molecules. Moreover, the composite foams exhibited excellent selective adsorption capacity and reusability. The study indicates that the conductive polymer could find its share in developing high-performance adsorbents.

Dye wastewater is becoming one of the most significant sources of water pollution, and its impact on human survival is immeasurable. In this study, we successfully synthesized a nanofiber membrane with environmentally friendly and efficient properties using electrospinning of a mixture of sodium alginate (SA) and copper oxide (CuO) nanoparticles, aimed at effective dye removal. The adsorption performance of the SA/CuO nanofiber membrane was evaluated using the cationic dye methylene blue (MB). The maximum adsorption capacity of the nanofiber membrane was increased significantly with the addition of CuO nanoparticles, reaching a maximum value of 1633.4 mg g-1, almost twice as much as that of pure SA membrane. The adsorption kinetics follows the pseudo-second-order model, where chemisorption acts as the rate-limiting step. The adsorption isotherm data indicate that the adsorption is monolayer. The nanofibrous membranes showed better dye removal under an alkaline environment. After four cycles of adsorption/desorption, the MB removal efficiency remained at 70.1% of the original adsorption capacity. The addition of CuO nanoparticles facilitated the adsorption of MB dyes, while the form of the nanofibrous membrane is easily recoverable and reusable. Therefore, the as-prepared SA/CuO nanofibrous composite membrane is a potentially favorable adsorbent material for wastewater treatment applications.

Starch-based flocculants are environmentally friendly and high-performance products, potentially applied in wastewater treatment with low operation cost and ecological risk. In this study, we successfully synthesized a ternary anionic copolymer of starch-acrylic acid-itaconic acid (SAI) through graft copolymerization. The synthesis conditions were optimized based on flocculation efficiency against cationic crystal violet (CV), and subsequent applicability was conducted under various environmental conditions. The results indicate that SAI exhibited outstanding decolorization efficiency under wide scopes of pH, temperature, and ionic strength. Most importantly, SAI achieved a remarkable decolorization rate of 91.2 % for 100 mg/L CV dye at a low concentration of 25 mg/L, accounting for one-fourth of the cost operated with commercial polyacrylamide. Compared to binary flocculants, SAI demonstrates superior flocculation performance too. The flocculation mechanism is primarily attributed to the combined effects of charge neutralization, bridging, and sweeping. SAI flocculants possess characteristics of high efficiency, environmental friendliness, and cost-effectiveness, thus presenting broad prospects for the treatment of dye wastewater.

Hollow vesicles are promising in water treatment due to their unique structure of the membrane and inner cavity. However, the adsorption capacity needs to be improved for targeted pollutants. Herein, millimeter-scale hollow vesicles were prepared with a one-step process of sequential stirring and grafting using chitosan, diallyldimethylammonium chloride, and sodium alginate as raw materials with the purpose of efficient removal of anionic dyes from wastewater. The composite vesicles were characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. The hollow vesicles showed the structure of the cationic membrane and the inner cavity, facilitating the dye adsorption. The adsorption capacity for the anionic dye Reactive Black 5 reached 698.1 mg/g, more than twice that of the binary composite vesicles without graft. The adsorption kinetics and isotherm data coincided with the pseudo-secondorder and Langmuir models, respectively, and the adsorption mechanism was monolayer chemisorption. Moreover, the vesicles worked well in wide ranges of environment pH, temperature, and co-existing pollutants. They also possessed excellent cyclic regeneration performance, in which 93 % of the initial adsorption capacity was maintained after four cycles. These results indicate that the millimeter-scale hollow vesicles exhibit broad application prospects for wastewater purification.

The flocculants based on naturally derived polymers are promising due to their wide availability and biodegradability. However, the flocculation performance and cost-effectiveness are less than satisfactory. This study developed novel flocculants with cationic etherified starch-acrylamide-dimethyl diallyl ammonium chloride (CAD), specifically designed for the efficient removal of anionic dyes. The synthesis conditions were optimized through the flocculation efficiency of anionic acid black-172 (AB) dye. Experimental results showed that CAD achieved a removal ratio of 91.6 +/- 1.8% with a flocculant dosage of 150 mg/L and maintained excellent decolorization efficiency across different pH, environmental temperatures, and ionic strengths. Most importantly, the synergistic effect with the presence of metal ions, particularly Fe3+, on the decolorization efficacy of CAD was observed. In the presence of Fe3+ (0.02 mol/L), the required flocculant dosage was reduced by two-thirds, while the maximum dye removal ratio reached 94.2 +/- 1.9%. The study indicates that the high efficiency of CAD primarily originates from dual mechanisms of charge neutralization and bridging. Furthermore, the operation cost of removing an equivalent amount of AB dye with CAD is about 40% of that incurred using commercial cationic polyacrylamide, highlighting its economic advantage in industrial applications. In summary, the CAD flocculant shows great promise for complex wastewater treatment.

Natural polymer based flocculants are prospective in water treatment on account of their advantages of wide source, simple operation process and ecological safety. However, its flocculation performance and cost effectiveness are usually not as satisfactory. In this work, xanthan gum-acrylamide-carboxymethyl cellulose (XAC) ternary anionic flocculant was synthesized with hydrothermal copolymerization. The polymerization conditions of raw material ratio, initiator dose, copolymerization time and reaction temperature were optimized by flocculation tests. The decolorization ratio of 82.9 % was obtained with XAC dosage of 35 mg/L for the 100 mg/L crystal violet aqueous solution. The as-prepared flocculants showed super decolorization ability and fast flocculation kinetics. The flocculation mechanism includes charge neutralization and bridging effects. More importantly, the operating expense of XAC is approximately 50 % of traditional polyacrylamide flocculant. In virtues of ecofriendliness, superior flocculation capacity and low expense, XAC flocculants show great promise for sewage treatment and open up a novel area for the natural polymer utilizations.

Polyaniline is widely used in the field of electrochemistry due to its excellent electrical conductivity. However, its effectiveness and mechanism of enhancing adsorption property are unclear. Herein, chitosan/polyaniline nanofibrous composite membranes with average diameter ranging from 200 to 300 nm were fabricated by electrospinning technology. The as-prepared nanofibrous membranes exhibited significantly improved adsorption capacity of 814.9 mg/g and 618.0 mg/g towards acid blue 113 and reactive orange dyes, which were 121.8 % and 99.4 % higher than that of pure chitosan membrane. The doped polyaniline promoted the dye transfer rate and capacity due to the enhanced conductivity of the composite membrane. Kinetic data showed that chemisorption was the rate-limiting step, and thermodynamic data indicated the adsorption of the two anionic dyes was spontaneous monolayer adsorption. This study provides a feasible strategy to introduce conductive polymer into adsorbent to construct high performance adsorbents for wastewater treatment.

Natural polymer flocculant possesses an exciting prospect in water treatment due to its non-toxicity, wide source, low cost and biodegradability. In this work, we have successfully synthesized the anionic terpolymer of car-boxymethyl cellulose-itaconic acid-sodium alginate (CIS) by microwave-assisted copolymerization. By studying the flocculation properties towards cationic dye of crystal violet (CV), the optimum synthesis conditions were determined. The maximum removal rate of 100 mg/L CV simulated wastewater was 92.2 % with CIS concen-tration of 30 mg/L. The flocculation kinetic results showed the rapid dye removal rate and the dye decolorization ratio of 89.8 % could be obtained at 75 s. Moreover, the CIS flocculant showed excellent flocculation effects in ambient pH of 4-10, flocculation temperature of 10-40 degrees C, and various inorganic salts. In general, the anionic CIS flocculant shows excellent cost effectiveness, where the predicted operation cost of as-prepared CIS is about 60 % of conventional polyacrylamide flocculant. It also has the advantages of excellent ecofriendliness and rich raw material source, indicative its potential applications of wastewater treatment.

Dye wastewater causes great harm to the natural environment and health. To prepare a high-efficient and cost-effective flocculant to deal with the cationic dye wastewater is still an enormous challenge. In this paper, an anionic copolymer of lignocellulose, acrylamide and carboxymethyl cellulose (LAC) was designed and synthesized by microwave-assisted copolymerization technique. The synthetic parameters of monomer ratio, amount of initiator and irradiation time were optimized as 1:1:2, 1.0% (w/w), and 16 min, respectively, according to the flocculation efficiency towards cationic dye of methylene blue. When the dye concentration was 400 mg/L and the dosage of LAC was 21 mg, the optimum color removal ratio can reach 92.0 ± 2.2%. LAC displayed superior flocculation performance in a wide range of flocculant dosage and wastewater pH. The flocculation mechanism mainly involves electric neutralization and bridging. In addition, the treatment cost of LAC is 32% lower than that of commercial anionic PAM, offering excellent flocculation performance and cost-effectiveness. The LAC flocculant has the advantages of wide source of raw materials, low price, simple synthesis process and good flocculation performance, which has great use potential in the field of wastewater treatment.

The coexistence of anionic and cationic dyes in dye wastewater has highlighted a great necessity to develop amphoteric adsorbents for their simultaneous removal. Herein, an amphoteric composite sponge was successfully fabricated by combining chitosan with electrospun sodium alginate nanofiber using lyophilization in acetic acid/water/dioxane mixed solvents, which owned the abundant functional groups and superior microstructure of interconnected pores and nanoscale fibers, beneficial for the adsorption capacity improvement. The optimum adsorption capacities for Acid Blue-113 and Rhodamine B were 926.2 ± 25.7 mg/g and 695.4 ± 17.0 mg/g, respectively, much higher than that of the controlled sample prepared with chitosan and non-spinning sodium alginate in traditional acetic acid/water solvents. Meanwhile, the sponge provided with the superior adsorption performance under various pH environment and cyclic adsorption. Importantly, it had considerable simultaneous adsorption capacity for binary system containing anionic and cationic dyes. Overall, the chitosan/electrospun sodium alginate nanofiber composite sponge shows potential for complex wastewater treatment.

Flocculants synthesized from biopolymers show the virtues of low cost, excellent efficiency and environmental friendliness. In this study, starch-acrylic acid-carboxymethyl cellulose (SAC) tertiary anionic copolymers were prepared by graft copolymerization. The optimal synthesis process was determined as raw material ratio of 1:3:1, acrylic acid neutralization degree of 70%, initiator dosage of 1.0 wt%, reaction temperature of 75 degrees C and reaction time of 5 h according to the flocculation performance towards methylene blue simulated waste water. Results demonstrated that the decolorization ratio of methylene blue (100 mg/L) could be up to 81.3% at the SAC dosage of 350 mg/L. The SAC achieved rapid flocculation kinetics and excellent color removal over a broad range of pH, ambient temperature and ionic strength. Furthermore, the operation cost of SAC is only one-fourth of industrial anionic polyacrylamide. The prepared SAC flocculant is promising for industrial dye wastewater treatment owing to its green raw materials, high efficiency and low operation cost.

Biopolymer hollow spheres have shown great promise for wastewater treatment due to their unique structure and properties. However, challenging issues like low efficiency and poor recyclability still exist for most hollow spheres. In this study, the modification of chitosan/carboxymethyl cellulose (CS/CMC) with Fe3O4 nanoparticles for the formation of bifunctional CS/CMC-Fe3O4 hybrid hollow spheres were prepared using a facile two stage mixing route, which exhibited excellent adsorption and catalytic degradation of dyes. The removal ability of the synthesized hollow spheres towards acid blue-113 (AB) and reactive orange C-3R (RO) using persulfate oxidation system was greatly improved compared with single adsorption or catalysis. The removal ratio of AB and RO could reach up to 96.2 and 97.5%, respectively. The kinetic process conformed to the quasi-second-order kinetics and the adsorption process was the controlling step of dye removal. In addition, the created hollow spheres showed excellent environmental adaptability and regenerative capability. This study provides a convenient and practical method for catalyst loading on biomass hollow spheres, which has perspective applications in wastewater purification.

Molecular imprinting technique is an efficient method to improve the selective adsorption capacity for the target pollutant. In this study, sodium alginate/polyethylene oxide molecularly imprinted nanofibrous membrane (SA/PEO-MINM) with average diameter of 185 ± 20 nm was successfully synthesized by electrospinning for selective adsorption of methylene blue (MB). Benefiting from the molecular imprinted technology, the adsorption amount of SA/PEO-MINM for MB was increased by about 65%, significantly higher than the non-imprinted membrane. Results showed that the adsorption equilibrium could be well fitted with Langmuir isotherm model and the maximum adsorption capacity towards MB was 3186.7 mg/g. Kinetic experiments well complied with the Pseudo second order model. Reusability studies indicated that the removal efficiency of MB could maintain 93% of the original adsorption capacity after four consecutive adsorption/desorption cycles. More importantly, the SA/PEO-MINM with high surface area and specific adsorption recognition sites showed excellent selective adsorption capacity in the adsorption experiment of MB and methylene orange mixed dye solution. In general, the SA/PEO-MINM can be successfully applied for the selective removal of MB from dye wastewater.

To effectively remove the toxic dyes from wastewater, sodium alginate (SA)/beta-cyclodextrin (beta-CD) nanofibrous composite membranes with average fiber diameters of 167-174 nm are obtained by an electrospinning method. The adsorption capacity of the SA/beta-CD membrane for methylene blue is 2776 mg g(-1), much higher than that of a pure SA membrane (1780 mg g(-1)). The incorporation of beta-CD also improves the adsorption rate significantly. The adsorption mechanism is mainly the synergy of the electrostatic attraction of SA and the host-guest interaction of beta-CD. Meanwhile, the SA/beta-CD nanofibrous membranes can be used in a wide pH range, and maintain excellent adsorption capacity after four cycles. The rapid adsorption efficiency and excellent adsorption capacity of SA/beta-CD nanofibrous membrane endows great potential in the field of wastewater treatment.

To effectively remove the dyes from wastewater, novel carboxymethyl cellulose/chitosan-CuO giant vesicles with dual function of adsorption and catalytic degradation were prepared. The vesicles were facilely obtained via blending chitosan solution and carboxymethyl cellulose/CuO mixed solution with sequent fast and slow stirring. The removal ratios of methyl orange (MO) and acid black-172 (AB) can reach 86.3% and 88.6% with the catalytic oxidation system of ammonium persulfate and vesicles. Compared with the CuO catalysis without the vesicles, the degradation rates of MO and AB increased by 1.3 and 3.1 times, respectively. The enhanced dye removal is ascribed to the excellent dye adsorption capacity of giant vesicles. Furthermore, the giant vesicles worked well in wide ranges of environmental pH and temperature, and exhibited excellent stability and reusability. This study provides a facile method to load catalyst onto polymeric giant vesicle with outstanding performance for the adsorption and catalytic degradation of dyes.