Characterization and flocculation evaluation of a novel carboxylated chitosan modified flocculant by UV initiated polymerization

Copolymers functionalized with quaternary ammonium compounds under template chain exhibit simultaneously efficient bactericidal and flocculation properties: Characterization, performance and mechanism

In this work, novel multifunctional cationic template copolymers with flocculation and sterilization capabilities were synthesized using a low-pressure ultraviolet (LP-UV) template polymerization method for the removal of kaolin and Escherichia coli (E. coli) from water. The influence of template agents on the structural performance of the copolymers was evaluated through characterization, which showed that template copolymer TPADM possesses a higher cationic charge density and a more complex rough surface, contributing to better flocculation performance than that of the non-template copolymer CPADM. Under optimal experimental conditions, TPADM-1 exhibited removal rates of 98.45% for kaolin and 99% for E. coli (OD600 =0.04), marginally outperforming the non-template copolymer. Simultaneously, TPADM-1 produced good adaptability to kaolin and E. coli wastewater in terms of wide pH, speculating that charge neutralization, adsorption bridging, patching, and sweeping simultaneously dominate the flocculation mechanism. Interestingly, SEM and 3D-EEM analysis confirm that the sterilization of E. coli occurs through two distinct functions: initially adsorption followed by subsequent cell membrane rupture and leakage of cellular contents, ultimately leading to cell death. This research further confirms the feasibility of the designed novel multifunctional copolymers for achieving simultaneous disinfection and turbidity removal, demonstrating practical applicability in real water treatment processes.

Dielectric barrier discharge plasma-modified chitosan flocculant and its flocculation performance

The flocculation performance of chitosan can be enhanced by grafting modification to overcome its disadvantages of poor water solubility. In this study, chitosan was modified by dielectric barrier discharge plasma and polymerized with acrylamide and aluminum chloride to synthesize a new chitosan-based flocculant, namely, chitosan-acrylamide-aluminum chloride (CA-PAC). After optimizing the synthesis conditions of CA-PAC, the best conditions were as follows: discharge time of 3 min, discharge power of 50 W, polymerization temperature of 60 °C, polymerization time of 3 h, total monomer concentration of 100 g/L, and m(AlCl3):m(CA) ratio of 2:1. Characterization was performed through SEM, XPS, FTIR, XRD, TG and 1H NMR. Results showed that the preparation of CA-PAC was successful. The influences of flocculant dosage, pH, and stirring intensity on flocculation efficiency were investigated. The removal efficiency of turbidity was 94.1 %. The investigation of the flocculation mechanism revealed that CA-PAC mainly relied on charge neutralization or the synergic action of electric neutralization, bridging, and roll-sweep under acidic and neutral conditions, but it depended on the joint action of adsorption bridging and net sweeping under alkaline conditions. This study provides new ideas for the preparation and development of modified chitosan and broadens its application in water treatment.

Ethylenediamine pretreatment simultaneously improved carbohydrate hydrolysis and lignin valorization

Lignocellulosic biomass (LCB) is the promising feedstock for value-added products, which would contribute to the bioeconomy and sustainable development. The efficient pretreatment is still required in the biorefinery of LCB. To make a simultaneous utilization of carbohydrates and lignin, a novel easy-recycled ethylenediamine (EDA) pretreatment was designed and evaluated in the present study. The results highlighted that this pretreatment yielded 96% glucose and 70% xylose in enzymatic hydrolysis. It simultaneously promoted the depolymerization of lignin into small molecules and functionalized the yielded lignin with Schiff base and amide structures. These animated-lignins showed a pH-responsive behavior and the excellent flocculation capacity by reducing more than 90% turbidity of kaolin suspensions. Therefore, easy-recycled EDA pretreatment hold the promise to simultaneously enhance the enzymatic hydrolysis of carbohydrates and endowed the new functionality of lignin toward downstream valorization, which improved the process feasibility and potentially enable the sustainability of LCB utilization.

Insight into the purification of algael water by a novel flocculant with enhanced branched nanochitosan structure

For improving inadequate nanostructural stability and promote algal removal efficiency, a novel nanochitosan-grafted flocculant (PAD-g-MNC) with an enhanced branched nanostructure and high molecular weight (MW) was fabricated via maleic anhydride acylation polymerization. Characterization results verified the successful synthesis of the flocculant and the formation of an irregular particle nanostructure. PAD-g-MNC exhibited superior algal and extracellular organic matter (EOM) removal and obtained the turbidity and chlorophyll-a removal rates of 93.46%-95.39% and 95.10%-97.31%, respectively, at the dosage of 4-5 mg L^-1. The growth rate, strength factor, and recovery factor of algal flocs flocculated by PAD-g-MNC were 90.36, 0.63, and 0.27 (100 rpm), respectively, and were higher than other flocculants prepared through conventional methods. Results indicated that the high intrinsic viscosity and stability branched nanostructure promoted the formation of stable flocs and regeneration ability of flocs. MW distribution and three-dimensional fluorescence analyses revealed that the special structure of PAD-g-MNC was beneficial to the removal of tryptophan-like proteins in EOM. Strong adsorption-adhesion and bridging-netting effects of the nanostructure chain were the dominated mechanisms in the improvement of flocculation efficiency. This study provided theoretical and experimental guidance for the design of flocculants with superior performance and efficient algal water purification performance.

High performance, cost-effective and ecofriendly flocculant synthesized by grafting carboxymethyl cellulose and alginate with itaconic acid

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 carboxymethyl 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 concentration 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 °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.

High-quality Chlorella vulgaris biomass harvesting through chitosan and polyacrylamid2e

Microalgal biomass is an emerging source of renewable energy and health-related compounds. However, harvesting of microalgae is a techno-economic hinder. In this research, chitosan and polyacrylamide were optimized harvesting condition for Chlorella vulgaris. Stirring at 300 rpm for 2 min is optimum for chitosan and polyacrylamide. Low-dose (10 mg/L) chitosan (flocculation efficiency (FE), 98.10 ± 1.06%) is more efficient than high-dose (25 mg/L) polyacrylamide (FE 94.57 ± 0.55%) for harvesting C. vulgaris. Chitosan resulted flocs settled more quickly than polyacrylamide, while polyacrylamide keep > 90% FE in a wider pH range (7-10) than chitosan (7-8). Chitosan and polyacrylamide both have no negative effect on biomass composition, including protein, carbohydrate, and carotenoid. C. vulgaris in flocs could successfully regrow in fresh culture media. The residual culture media was recycled with little impact on cell growth. All the results suggested that chitosan and polyacrylamide could harvest high-quality microalgal biomass.

Adsorption and interaction mechanisms of Chi-g-P(AM-DMDAAC) assisted settling of kaolinite in a two-step flocculation process

Flocculation has been widely employed in treatment of mineral tailings and water management. In this study, a chitosan-graft-poly(acrylamide-dimethyl diallyl ammonium chloride) (Chi-g-P(AM-DMDAAC)) was synthesized in-house. The adsorption and interaction mechanisms of Chi-g-P(AM-DMDAAC) and an anionic polyacrylamide (APAM) in a two-step flocculation process of kaolinite were explored using settlement tests, zeta potential measurement, quartz crystal micro-balance with dissipation (QCM-D) and atomic force microscopy (AFM) technique. The type of primary flocculant was critical for the two-step flocculation process. The treatment of the kaolinite suspension using 1 mg/L of Chi-g-P(AM-DMDAAC) followed by adding 2 mg/L of APAM displayed more efficient flocculation performance. QCM-D results showed that three dissipative layers were assembled on model kaolinite surface after sequentially injecting 3.5 mg/L of Chi-g-P(AM-DMDAAC), 0.05 wt% kaolinite suspension and 2.5 mg/L of APAM. The above total adsorption amount (Δf of -64.9 Hz) was much higher than that of using the two flocculants in reverse order (Δf of -23.1 Hz). This result indicated that the adsorption layer of the positively charged Chi-g-P(AM-DMDAAC) on kaolinite surface provided active adsorption sites for APAM. Further AFM measurement confirmed that the average adhesion between the silicon tip adsorbed Chi-g-P(AM-DMDAAC) and model kaolinite surface in 2.5 mg/L APAM solution increased from 0.25 ± 0.1 nN to 4.2 ± 0.3 nN with the effective interaction range of 700 nm, which was stronger than that measured between a bare silicon tip and silica substrate in single-component-flocculant solutions. The highly efficient two-step flocculation process could be ascribed to the strong electrostatic attraction between the kaolinite and the oppositely charged Chi-g-P(AM-DMDAAC) and APAM. Findings in this study will benefit the development of environmentally friendly flocculant for mineral tailings and water treatment.

Synthesis and characterization of cinnamic acid conjugated N-(2-hydroxy)-propyl-3-trimethylammonium chitosan chloride derivatives: A hybrid flocculant with antibacterial activity

The modified natural biopolymers, recognized as environmentally friendly flocculants, are gaining tremendous attention in the field of water treatment. In this study, a novel hybrid flocculant with antibacterial activity, cinnamic acid (CA) conjugated N-(2-hydroxy)-propyl-3-trimethylammonium chitosan chloride (HTCC) derivative (HTCC-CA), was prepared via quaternary ammonium and amide reactions. The characterization, flocculation, and antibacterial activities were carried out to access the structural properties and potential application. The results of UV-vis, FT-TR, and ¹H NMR confirmed the successful synthesis of HTCC-CA1-3 derivatives. XRD and TGA revealed the lower crystallinity and thermal stability of HTCC-CA1-3 derivatives than chitosan (CS). Bacterial flocculation and antibacterial tests indicated the excellent flocculation effect of HTCC-CA1-3 derivatives and showed high antibacterial activity for Escherichia coli suspension. Moreover, the mechanism of action of the derivatives was investigated via zeta potential measurements and scanning electron microscope, which can be summed up as the effective interaction between charges. The results proved that HTCC-CA derivatives are promising agents for wastewater treatment.

Advanced Treatment of Phosphorus Pesticide Wastewater Using an Integrated Process of Coagulation and Ozone Catalytic Oxidation

Conventional pretreatment and secondary biochemical treatment are ineffective methods for removing phosphorus from phosphorus-containing pesticide wastewater. In this study, coagulation-coupled ozone catalytic oxidation was used to treat secondary biochemical tailwater of phosphorus-containing pesticide wastewater thoroughly. The effects of the coagulant type, coagulant dosage, coagulant concentration, wastewater pH, stirring rate, and stirring time on the removal efficiency of chemical oxygen demand (COD), total phosphorus (TP), and chromaticity were investigated during coagulation. When the dosage of the coagulant PAFS was equal to 100 mg/L, the concentration of the coagulant, pH, stirring rate, and stirring time were 5 wt%, 8, 100 rpm, and 5 min, respectively, and the removal rates of COD, TP, and chroma in wastewater reached the maximum value of 17.6%, 86.8%, and 50.0%, respectively. Effluent after coagulation was treated via ozone catalytic oxidation. When the respective ozone dosage, H2O2 dosage, catalyst dosage, and reaction time were 120 mg/L, 0.1 vt‰, 10 wt%, and 90 min, residual COD and chromaticity of the final effluent were 10.3 mg/L and 8, respectively. The coagulation-coupled ozone catalytic oxidation process has good application prospects in the treatment of secondary biochemical tailwater from phosphorus-containing pesticide wastewater.

Preparation of silane-dispersed graphene crosslinked vinyl carboxymethyl chitosan temperature-responsive hydrogel with antibacterial properties

We synthesized a temperature-sensitive antibacterial hydrogel, defined as NIPAM-CG/GM hydrogel. First, vinyl carboxymethyl chitosan (CG) was synthesized as a crosslinking carrier and silane dispersed graphene (GM) was synthesized as a reinforcer. Then, the N-isopropylacrylamide (NIPAM) monomer was free-radical polymerized with the vinyl groups of CG and GM to form a NIPAM-CG/GM hydrogel without any crosslinking agent. The influences of different hydrogel compositions on the microstructure, compressive properties, swelling, drug loading, and drug release properties of the hydrogels were discussed, and its temperature sensitivity was also demonstrated. The results showed that the lower critical solution temperature (LCST) and mechanical properties of the hydrogel could be adjusted by controlling the amount of CG and GM. Next, its biocompatibility was characterized, and its antibacterial performance was tested against Escherichia coli and Staphylococcus aureus. The antibacterial mechanism was explained by measuring the difference in the ion concentration outside the membrane and changes in the morphology of live/dead bacteria. NIPAM-CG/GM had a high drug loading and nearly complete drug release at a physiological temperature of 37 °C. Its moderate mechanical properties, excellent biocompatibility, and antibacterial effects give NIPAM-CG/GM great potential applications as a wound dressing.

Research on a new cationic polyacrylamide (CPAM) with a cationic microblock structure and its enhanced effect on sludge condition and dewatering

Flocculation is one of the commonly used sludge conditioning methods in water supply plants, which can improve the sludge dewatering performance by reducing the specific resistance of sludge (SRF), decreasing the amount of sludge, and finally lowering the transportation cost and subsequent disposal cost of sludge. Therefore, it is particularly important to develop new and efficient flocculants. In this paper, the template copolymer of acryloxy trimethylammonium chloride (DAC) and acrylamide (AM) was successfully synthesized by microwave-template copolymerization (MV-TP) using sodium polyacrylate (NaPAA) as template. The template copolymer was analyzed by infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), nuclear magnetic resonance hydrogen spectroscopy (¹H NMR), and scanning electron microscopy (SEM). It was found that this template copolymer had obvious cationic microblock structure. In addition, the test results of association constant (K_M) and polymerization kinetics showed that the MW-TP was assigned to free radical initiated polymerization and the polymerization mechanism was I Zip-up (ZIP). It confirmed the formation of cation fragment structure again. Due to its dense positive charges in this new cationic microblock structure, it greatly improved the functions of electric neutralization, electrical patching, and adsorption bridging. The cationic fragment structure in the template copolymer could help to generate large and dense floc structure and form stable drainage channels. Under external pressure, these large and compact floc structures had greater compressive resistance, which avoided deformation and blockage of drainage channels and voids. It was beneficial to reduce SRF and evidently enhanced sludge dewatering performance.

Heavy metal removal from aqueous solutions by chitosan-based magnetic composite flocculants

In this study, three magnetic flocculants with different chelating groups, namely, carboxymethyl chitosan-modified Fe₃O₄ flocculant (MC), acrylamide-grafted magnetic carboxymethyl chitosan flocculant (MCM), and 2-acrylamide-2-methylpropanesulfonic acid copolyacrylamide-grafted magnetic carboxymethyl chitosan flocculant (MCAA) were prepared, synthesized, and characterized by photopolymerization technology. They were applied to the flocculation removal of Cr(III), Co(II), and Pb(II). The effect of flocculation condition on the removal performance of Cr(III), Co(II), and Pb(II) was studied. Characterization results show that the three magnetic carboxymethyl chitosan-based flocculants have been successfully prepared with good magnetic induction properties. Flocculation results show that the removal rates of MC, MCM, and MCAA on Cr(III) are 51.79%, 82.33%, and 91.42%, respectively, under the conditions of 80 mg/L flocculant, pH value of 6, reaction time of 1.5 hr, G value of 200 s^-1, and precipitation magnetic field strength of 120 mT. The removal rates of Co(II) by MC, MCM, and MCAA are 54.33%, 84.99%, and 90.49%, respectively. The removal rates of Pb(II) by MC, MCM, and MCAA are 61.54%, 91.32%, and 95.74%, respectively. MCAA shows good flocculation performance in composite heavy metal-simulated wastewater. The magnetic carboxymethyl chitosan-based flocculant shows excellent flocculation performance in removing soluble heavy metals. This research provides guidance and ideas for the development of efficient and low-cost flocculation technology to remove heavy metals in wastewater.

Biopolymer-based flocculants: a review of recent technologies

Biopolymer-based flocculants have become a potential substitute for inorganic coagulants and synthetic organic flocculants due to their wide natural reserves, environmental friendliness, easy natural degradation, and high material safety. In recent years, with more and more attention to clean technologies, a lot of researches on the modification and application of biopolymer-based flocculants have been carried out. The present paper reviews the latest important information about the base materials of biopolymer-based flocculants, including chitosan, starch, cellulose, and lignin etc. This review also highlights the various modification methods of these base materials according to reaction types in detail. Via the recent researches, the flocculation mechanisms of biopolymer-based flocculants, such as adsorption, bridging, charge neutralization, net trapping, and sweeping, as well as, some other special mechanisms are comprehensively summarized. This paper also focuses on the water treatment conditions, the removal efficiency, and advantages of biopolymer-based flocculants in applications. Further, this review sheds light on the future perspectives of biopolymer-based flocculants, which may make progress in the sources of base materials, modification processes, multi-function, and deepening application researches. We believe that this review can guide the further researches and developments of biopolymer-based flocculants in the future, to develop them with a higher efficiency, a lower cost, more safety, and multi-function for more diversified applications. Graphical abstract.

Polymeric nanocapsules: A review on design and production methods for pharmaceutical purpose

Polymeric nanocapsules have extensive application potential in medical, biological, and pharmaceutical fields, and, therefore, much research has been dedicated to their production. Indeed, production protocols and the materials used are decisive for obtaining the desired nanocapsules characteristics and biological performance. In addition to that, several technological strategies have been developed in the last decade to improve processing techniques and form more valuable nanocapsules. This review provides a guide to current methods for developing polymeric nanocapsules, reporting aspects to be considered when choosing appropriate materials, and discussing different ways to produce nanocapsules for superior performances.

Preparation and Characterization of High-Efficiency Magnetic Heavy Metal Capture Flocculants

In this study, a high-efficiency magnetic heavy metal flocculant MF@AA was prepared based on carboxymethyl chitosan and magnetic Fe3O4. It was characterized by SEM, FTIR, XPS, XRD and VSM, and the Cu(II) removal rate was used as the evaluation basis for the preparation process. The effects of AMPS content, total monomer concentration, photoinitiator concentration and reaction time on the performance of MF@AA flocculation to remove Cu(II) were studied. The characterization results show that MF@AA has been successfully prepared and exhibits good magnetic induction characteristics. The synthesis results show that under the conditions of 10% AMPS content, 35% total monomer concentration, 0.04% photoinitiator concentration, and 1.5 h reaction time, the best yield of MF@AA is 77.69%. The best removal rate is 87.65%. In addition, the response surface optimization of the synthesis process of MF@AA was performed. The optimal synthesis ratio was finally determined as iron content 6.5%, CMFS: 29.5%, AM: 53.9%, AMPS: 10.1%. High-efficiency magnetic heavy metal flocculant MF@AA shows excellent flocculation performance in removing Cu(II). This research provides guidance and ideas for the development of efficient and low-cost flocculation technology to remove Cu(II) in wastewater.

Optimized pre-treatment of high strength food waste digestate by high content aluminum-nanocluster based magnetic coagulation

Coagulation-based pre-treatment efficiency of high strength digestate of food waste (HSDFW) anaerobic digestion is negated by organic ligand-catalyzed decomposition of coagulants. In this study, an efficient HSDFW pre-treatment method, magnetic seeds (MS) coagulation, was employed by using highly stable Keggin Al₃₀ nanocluster (PAC₃₀), MS and polyacrylamide (PAM), and its operation was optimized by evaluating the performance of removing turbidity, total suspended solids (TSS), chemical oxygen demand (COD), and total phosphorous (TP) phosphate. Results showed that at the optimum dosage of 4.82 g/L, PAC₃₀ demonstrated excellent removals as high as 98.93% ± 0.1% of turbidity, 98.04% ± 0.1% of TSS, 58.28% ± 0.3% of total COD, 99.98% ± 0.01% of TP and 99.50% ± 0.01% of dissolved phosphate, respectively. Apparent molecular weight (AMW) and three-dimensional excitation-emission matrix (3D-EEM) fluorescence spectroscopy analyses demonstrated more efficient removal of dissolved organic matter (DOM), particularly non-biodegradable and hydrophobic components by PAC₃₀ than commercial coagulant. The sedimentation was much improved from 40 min by coagulation/flocculation to about 5 min settling by MS coagulation. The PAC₃₀ based magnetic coagulation (MC) presents theoretical guidance on a cost-effective and much less footprint pre-treatment alternative for high strength wastewater.

Magnetic flocculation of Cu(II) wastewater by chitosan-based magnetic composite flocculants with recyclable properties

In this study, three magnetic flocculants, namely, MC, MC-g-PAM, and MC-g-PAA, were prepared. The structure characteristics, flocculation performance, and floc characteristics of the three magnetic flocculants were systematically studied and compared. SEM, FT-IR, XPS, XRD, TG-DSC, and VSM characterization results show that MC, MC-g-PAM, and MC-g-PAA are successfully prepared and exhibit good magnetic induction. The removal rates of copper ions by MC, MC-g-PAM, and MC-g-PAA under the optimal coagulation conditions are 93.39 %, 88.64 %, and 61.41 %, respectively. Kinetic fitting shows that the flocculation reaction process of MC and MC-g-PAM conforms to pseudo first-order kinetics, while the flocculation reaction process of MC-g-PAA conforms to pseudo second-order kinetics. The flocs produced by MC-g-PAA have larger particle size and fractal dimension than those by MC and MC-g-PAM. At 80 mg/L dosage and pH 6, the floc size and floc fractal dimension obtained by MC-g-PAA reach the maximum values of 48.28 um and 1.468, respectively. Zeta potential studies show that the flocculation functions of the three flocculants are mainly adsorption bridging, adsorption electric neutralization, and chelating precipitation. Recycling experiments show that MC-g-PAA has good recyclability, and the recovery rate after the fifth use is 77.24 % with the Cu(II) removal rate of 67.53 %.

Plasma-enhanced modification of polysaccharides for wastewater treatment: A review

In this work, novel polysaccharide-based sorbents modified with plasma technologies are discussed. Plasma selectively modifies the surface properties by generating specific moieties, enhancing adsorption performance, and the physical-chemical properties of the material without modifying its bulk properties. Among plasma technologies, cold plasma is more suitable and energy-efficient, since thermal-sensitive materials could be modified using this technology. Besides, atmospheric-pressure plasma systems possess the required features to scale-up plasma technologies for surface modification of sorbents. Moreover, a big challenge is the semi-continuous operation to modify sorbents as it would decrease overall process costs. Due to its low-cost and extensive availability, polysaccharide-based sorbents are promising substrates for plasma-enhanced modification to develop highly efficient adsorbents. The development of polysaccharide-based materials includes modified cellulose, chitosan, or lignocellulosic materials with functionalities that increase adsorption capacity and selectivity towards a specific organic or inorganic pollutant.

Synthesis and evaluation of cationic flocculant P(DAC-PAPTAC-AM) for flocculation of coal chemical wastewater

In this study, a high-efficiency cationic flocculant, P(DAC-MAPTAC-AM), was successfully prepared using UV-induced polymerization technology. The monomer Acrylamide (AM): Acryloxyethyl Trimethyl ammonium chloride (DAC): methacrylamido propyl trimethyl ammonium chloride (MAPTAC) ratio, monomer concentration, photoinitiator concentration, urea content, and cationic monomer DAC:MAPTAC ratio, light time, and power of high-pressure mercury lamp were studied. The characteristic groups, characteristic diffraction peaks, and characteristic proton peaks of P(DAC-MAPTAC-AM) were confirmed by fourier transform infrared spectroscopy (FTIR), X-Ray diffraction (XRD), ¹H nuclear magnetic resonance spectrometer (¹H NMR), and scanning electron microscopy (SEM). The effects of dosage, pH value, and velocity gradient (G) value on the removal efficiencies of turbidity, COD, ammonia nitrogen, and total phenol by poly aluminum ferric chloride (PAFC), P(DAC-MAPTAC-AM), and PAFC/P(DAC-MAPTAC-AM) in the flocculation treatment of coal chemical wastewater were investigated. Results showed that the optimal conditions for the flocculation of coal chemical wastewater using P(DAC-MAPTAC-AM) alone are as follows: dosage of 8-12 mg/L, G value of 100-250 s ^- 1, and pH value of 4-8. The optimal dosage of PAFC is 90-150 mg/L with a pH of 2-12. The optimal dosage for PAFC/P(DAC-MAPTAC-AM) is as follows: PAFC dosage of 90-150 mg/L, P(DAC-MAPTAC-AM) dosage of 8-12 mg/L, and pH range of 2-6. When P(DAC-MAPTAC-AM) was used alone, the optimal removal efficiencies of turbidity, COD, ammonia nitrogen, and total phenol were 81.0%, 35.0%, 75.0%, and 80.3%, respectively. PAFC has good tolerance to wastewater pH and good pH buffering. Thus, the flocculation treatment of coal chemical wastewater using the PAFC/P(DAC-MAPTAC-AM) compound also exhibits excellent resistance and buffering capacity.

Nonswelling injectable chitosan hydrogel via UV crosslinking induced hydrophobic effect for minimally invasive tissue engineering

Injectable chitosan hydrogels exhibit excellent biological properties for application in biomedical engineering, however most of these hydrogels have limited applicability because "Swelling" can induce volume expansion of conventional hydrogels implanted in the body damages the surrounding tissues. Here, we report a new "Nonswelling" pentenyl chitosan (PTL-CS) hydrogel via N‒acylation reaction to graft an UV crosslinkable short hydrophobic alkyl chain (n‒pentenyl groups). The incorporated pentenyl groups can be crosslinked by UV irradiation to form hydrophobic chains via combination termination, which generate strong hydrophobic effect to extrude the excess water in hydrogel, resulting in a "Nonswelling" state at biological temperature. Furthermore, the PTL-CS solution showed no cytotoxicity in vitro and minimally invasive treatment in vivo demonstrated the PTL-CS hydrogel no adverse effects in a rat model. The nonswelling injectable and UV crosslinkable chitosan hydrogel hold potential applications in smart biomaterials and biological engineering as well as providing a new natural hydrogel in minimally invasive tissue engineering..

A review on the synthesis of graft copolymers of chitosan and their potential applications

Chitosan is an antimicrobial, biodegradable and biocompatible natural polymer, commercially derived from the partial deacetylation of chitin. Currently modified chitosan has occupied a major part of scientific research. Modified chitosan has excellent biotic characteristics like biodegradation, antibacterial, immunological, metal-binding and metal adsorption capacity and wound-healing ability. Chitosan is an excellent candidate for drug delivery, food packaging and wastewater treatment and is also used as a supporting object for cell culture, gene delivery and tissue engineering. Modification of pure chitosan via grafting improves the native properties of chitosan. Chitosan grafted copolymers exhibit high significance and are extensively used in numerous fields. In this review, modifications of chitosan through several graft copolymerization techniques such as free radical, radiation, and enzymatic were reported and the properties of grafted chitosan were discussed. This review also discussed the applications of grafted chitosan in the fields of drug delivery, food packaging, antimicrobial, and metal adsorption as well as dye removal.

Chemical Modification of Cotton Fabrics by a Bifunctional Cationic Polymer for Salt-Free Reactive Dyeing

Cotton modification exhibited great potential in the fabric dyeing industry. A bifunctional cationic polymer with a moderate cationic degree and low molecular weight was achieved via free radical polymerization between dimethyl diallyl ammonium chloride and allyl glycidyl ether. Then, it was further utilized for the modification of cotton fabrics. The formation of the cationic polymer was identified using Fourier transform infrared and nuclear magnetic resonance spectroscopies. The structure and properties of both treated and untreated cotton were analyzed by X-ray photoelectron spectroscopy and scanning electron microscopy. The modified cotton fabrics could be salt-free dyed with reactive dyes at low temperatures. While obtaining satisfactory color fastness and leveling properties, the dyeability of the modified cotton was improved significantly compared with the conventional dyeing of native cotton. Besides, the prepared cationic polymer has good flocculating properties to avoid secondary pollution, suggesting high potential for achieving an economical and eco-friendly dyeing process.

Synthesis of the Hydrophobic Cationic Polyacrylamide (PADD) Initiated by Ultrasonic and its Flocculation and Treatment of Coal Mine Wastewater

In this study, a new type of hydrophobic cationic polyacrylamide P (AM-DMC-DABC) (PADD) was synthesized by ultrasonic (US)-initiated polymerization, which is used for the separation and removal of coal mine wastewater. The acrylamide (AM), methacryloyloxyethyl trimethyl ammonium chloride (DMC) and acryloyloxyethyl dimethylbenzyl ammonium chloride (DABC) were used as monomers to prepare). The factors that affecting the US initiated polymerization of PADD were analyzed. Fourier transform infrared spectroscopy (FT-IR), 1H nuclear magnetic resonance (1H NMR) and scanning electron microscopy (SEM) were used to characterize the chemical structure, thermal decomposition performance and surface morphology of the polymers. FT-IR and 1H NMR results showed that PADD was successfully synthesized. In addition, irregular porous surface morphology of PADD were observed by SEM analysis. Under the optimum conditions (pH = 7.0, flocculant dosage = 16.0 mg/L), the excellent flocculation performance (turbidity removal rate (TR) = 98.8%), floc size d50 = 513.467 μm, fractal dimension (Df) = 1.61, flocculation kinetics (KN0) = 27.24 × 10−3·s−1) was obtained by using high-efficiency flocculant PADD. Zeta potential analysis was used to further explore the possible flocculation mechanism of removal. The zeta potential and flocculation analytical results displayed that the flocculation removal process of coal mine wastewater mainly included hydrophobic effect, adsorption, bridging and charge neutralization, and electric patching when PADD was used. The PADD showed more excellent coal mine wastewater flocculation performance than PAD, commercial cationic polyacrylamide (CPAM) CCPAM and PAM. Thus PADD, with its good flocculation effect on coal mine wastewater under relatively wide pH range, had bright practical application value.

Assessment of a novel nanostructured flocculant with elevated flocculation and antimicrobial activity

In this work, a novel process involving the preparation of nanochitosan-grafted flocculants (CPAM-g-NCS) to treat low turbid and salmonella suspensions simultaneously was introduced. Nanotechnology was employed to enhance the adsorption-adhesion and sterilization abilities of dual-functional flocculants. The monomers of chitosan, acrylamide, methacryloyl ethyl trimethyl ammonium chloride, and sodium tripolyphosphate were utilized for flocculants copolymerization. Then, using fourier-transform infrared spectroscopy, nuclear magnetic resonance hydrogen spectrum, and thermogravimetric and differential scanning calorimetry analysis, the successful synthesis of CPAM-g-NCS was verified. Scanning electron microscopy and size analysis suggested that nanostructured flocculants with irregular morphology and nanocolloids of 60.44 nm were formed. CPAM-g-NCS was applied to treat a series of simulated low turbid and salmonella suspensions. The simulation results showed that the minimum residual turbidity of 1.97 NTU and optical density of 0.16 (initial 0.89) can be achieved at dosages of 2.5 and 8.75 mg L^-1, respectively, which were superior to conventional organics flocculants. Mechanistic studies suggested that the excellent adsorption property, and large numbers of quaternary ammonium and amino groups of nanoflocculants contributed to the superior flocculation and antibacterial performance of CPAM-g-NCS.

Combination of Coagulation and Ozone Catalytic Oxidation for Pretreating Coking Wastewater

In this study, coagulation, ozone (O₃) catalytic oxidation, and their combined process were used to pretreat actual coking wastewater. The effects on the removal of chemical oxygen demand (COD) and phenol in coking wastewater were investigated. Results showed that the optimum reaction conditions were an O₃ mass flow rate of 4.1 mg min⁻¹, a reaction temperature of 35 °C, a catalyst dosage ratio of 5:1, and a O₃ dosage of 500 mg·L⁻¹. The phenol removal ratio was 36.8% for the coagulation and sedimentation of coking wastewater under optimal conditions of 25 °C of reaction temperature, 7.5 reaction pH, 150 reaction gradient (G) value, and 500 mg·L⁻¹ coagulant dosage. The removal ratios of COD and phenol reached 24.06% and 2.18%, respectively. After the O₃-catalyzed oxidation treatment, the phenols, polycyclic aromatic hydrocarbons, and heterocyclic compounds were degraded to varying degrees. Coagulation and O₃ catalytic oxidation contributed to the removal of phenol and COD. The optimum reaction conditions for the combined process were as follows: O₃ dosage of 500 mg·L⁻¹, O₃ mass flow of 4.1 mg·min⁻¹, catalyst dosage ratio of 5:1, and reaction temperature of 35 °C. The removal ratios of phenol and COD reached 47.3% and 30.7%, respectively.