An investigation of the flocculation characteristics of polyacrylamide‐grafted chitosan

To investigate the flocculation characteristics of polyacrylamide (PAM)‐grafted chitosan, a series of PAM‐grafted chitosan copolymer (Chito‐g‐PAM1 to Chito‐g‐PAM4) have been synthesized by ceric ammonium nitrate‐induced solution polymerization technique in nitrogen atmosphere. The flocculation characteristics of the polymer samples (PAM, grafted and ungrafted chitosan) were studied by settling test and jar test methods in the colloidal suspensions of kaolin, iron ore, silica, and bentonite powder. It was found that the settling performance of Chito‐g‐PAM3 is best among the polymer samples. The jar test results indicate that the ungrafted chitosan has better water clarifying performance than both the PAM and grafted chitosan. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

A Review of the Use of Chitosan for the Removal of Particulate and Dissolved Contaminants

Abstract

Chitosan has unique properties among biopolymers, especially due to the presence of primary amino groups. Chitosan has been used for the chelation of metal ions in near‐neutral solution, the complexation of anions in acidic solution (cationic properties due to amine protonation), the coagulation of negatively charged contaminants under acidic conditions, and for precipitative flocculation at pH above the pKa of chitosan. The coagulation and flocculation properties can be used to treat particulate suspensions (organic or inorganic) and also to treat dissolved organic materials (including dyes and humic acid). This paper will give an overview of the principal results obtained in the treatment of various suspensions and solutions: (a) bentonite suspensions; (b) organic suspensions; (c) anionic dye solutions; and (d) humic acid solutions. Stoichiometry and charge restabilization were determined for the coagulation of humic acid, kaolin, and organic dyes with chitosan, indicating charge neutralization as the dominant mechanism for removal. Charge patch destabilization and bridging mechanisms were inferred in other cases, based on the effects of the apparent molecular weight of the chitosan preparations and effectiveness of sub‐stoichiometric doses of chitosan. For dye solutions, results showed that color can be removed either by sorption onto solid‐state chitosan or by coagulation‐flocculation using dissolved‐state chitosan; the reactivity of amine groups was significantly increased when dissolved chitosan was used. For humic materials, chitosan can be used as a primary coagulant or as a flocculant after coagulation with alum or other inexpensive coagulants. The influence of the degree of deacetylation and the molecular weight of chitosan on its performance as coagulant/flocculant is illustrated by several examples.     

Study of chitosan and its derivatives as preservatives for field natural rubber latex

In this study, the chitosan and its derivatives were tested for their preservative activities for field natural rubber (NR) latex. A series of chitosans with different molecular weights were obtained by nitrous acid depolymerization. The chemically modified chitosans, N‐carboxymethyl chitosan (NCMCh), N‐sulfated chitosan (NSCh), and N‐(2‐hydroxy)propyl‐3‐trimethylammonium chitosan chloride (NHTACh), were prepared from high and low‐molecular weight chitosans. Preservative activities for field NR latex of these chitosans were investigated based on the measurement of volatile fatty acids (VFA) number of the treated latex. The preservative activities of chitosan increased with decreasing molecular weights. The low‐ molecular weight NSCh and NHTACh exhibited good preservative activity for the latex. By the use of low‐molecular weight NHTACh in combination with octylphenol poly (ethyleneglycolether) (Nonidet P40), the latex was successfully preserved for more than 1 month in the low‐ammonia condition. The results showed an attractive feature to develop the preservative system, which was possible to reduce the concentrations of ammonia and carcinogenic nitrosamine in the NR latex. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Homogeneous synthesis and characterization of polyacrylamide‐grafted cationic cellulose flocculants

In this work, cationic cellulose (CC) with different degrees of substitution (DS) was successfully synthesized by the reaction between cellulose and 3‐chloro‐2‐hydroxypropyl‐trimethylammonium chloride (CHPTAC) in a 7 wt % NaOH and 12 wt % urea aqueous solution. The structure of the CC was characterized by using elemental analysis, ¹H‐NMR, and FTIR. The DS values of CC ranged between 0.18 and 0.50, which could be obtained by adjusting the reaction temperature, reaction time, and molar ratio of CHPTAC to anhydroglucose unit of cellulose. The cationic cellulose–graft–polyacrylamide flocculant (CC‐g‐PAM) based on CC and polyacrylamide (PAM) was also synthesized in a homogeneous aqueous solution. The flocculation characteristics of CC and CC‐g‐PAM were evaluated in a kaolin suspension. The results showed that CC‐g‐PAM was an effective flocculant for the kaolin suspension under acidic or neutral conditions, and the flocculation efficiency was over 90%, while the CC showed better flocculation performance under alkaline conditions. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43106.     

Development of antimicrobial membranes via the surface tethering of chitosan

To render the surface of ultrafiltration membranes biocidal, cellulose membranes were modified with chitosan, a naturally occurring polycationic biocide. Through the use of chitosans of different molecular weights and membranes with different pore sizes, the alteration of the morphological structure of tethered chitosan layers was achieved. The importance of such structural differences in the antimicrobial activity of the prepared membranes against gram‐positive Staphylococcus aureus and gram‐negative Escherichia coli was studied. The antimicrobial efficiency improved with the use of chitosans with higher molecular weights and membranes with smaller pore sizes. This suggested that the surface location of the grafted chitosan chains was more preferential for a higher antimicrobial activity of the surface. Membranes modified with chitosan showed higher antimicrobial efficiency against gram‐positive S. aureus than against gram‐negative E. coli. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation of new water‐soluble chitosan containing hyperbranched‐vinylsulfonic acid sodium salt and their antimicrobial activities and chelation with metals

In this work, an efficient and simple method to graft a vinylsulfonic acid sodium salt on a poorly water‐soluble chitosan is described. Commercially available low molecular weight chitosan is converted to water‐soluble chitosan containing hyperbranched‐vinylsulfonic acid sodium salt groups. The process comprises the following steps: Michael addition of methyl acrylate, amidation with ethylenediamine, and Michael addition of vinylsulfonic acid sodium salt. A variety of chitosans containing vinylsulfonic acid sodium salt, with improved water solubility, is synthesized by repeating these three steps. The new chitosan derivatives show better antimicrobial activity against Micrococcus luteus ATCC 10240 and Achromobacter xylosoxidans ATCC 2706. In addition, they display better chelating behavior with heavy metals, like cadmium(II), copper(II), and nickel(II), than the starting chitosan. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Fabrication of photochromic hydrogels using an interpenetrating chitosan network

The synthesis of a novel interpenetrating chitosan network post‐modified with spiropyran (SP) derivatives has been used to develop photochromic hydrogels. We have synthesized succinyl chitosan polymers containing a considerable number of both amines and carboxylic groups. Their intra/inter molecular amide coupling reactions and postmodification with SP derivatives resulted in the photochromic hydrogels functionalized with chitosan‐based interpenetrating polymer network structures. In this hydrogel system, SPs undergo reversible photoresponsive structural switching between a ring‐closed colorless SP form and a ring‐opened purple merocyanine form under specific light‐irradiation conditions. Notably, the photo‐mediated wettabilities and color intensities of the hydrogels increase by the increment in the molecular weight of SP‐functionalized chitosans. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45120.     

Coagulation–flocculation of colloidal suspensions of kaolinite,bentonite, and alumina by chitosan sulfate

This article reports on the removal of colloidal suspensions of kaolinite, bentonite, and alumina using chitosan sulfate (ChS). ChS was synthesized by partial introduction of sulfate groups in the chitosan (Ch) structure. The polyampholyte (chitosan sulfate) shows variable charge depending on the pH of the solution. ChS was characterized by FTIR, ¹³C‐NMR, elemental analysis, and potentiometric titrations. The ChS coagulation–flocculation capacity for kaolinite, bentonite, and alumina aqueous suspensions was systematically studied. The coagulation–flocculation process was carried out at various pH values and ChS concentrations. The pH range in which the largest ChS removal capacity was observed depended on particle type (4.5–5.5 for kaolinite, 4.5–7.0 for bentonite, and 7.0–8.0 for alumina). The removal of colloidal particles is explained by charge neutralization due to electrostatic interactions between ChS and particles and particle entrapping when the polyelectrolyte precipitates. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis and property studies of N‐carboxymethyl chitosan

N‐carboxymethyl chitosans (N‐CMC) were synthesized from chitosan in water with chloroacetic acid instead of comparatively expensive glyoxylic acid. The optimal reaction conditions were 90°C and 4 h with a ratio of chloroacetic acid to chitosan 5 : 1(w/w). The degree of substitution of product exceeded 1.32. The N‐carboxymethyl chitosans were characterized by XRD, FTIR, ¹H‐NMR, and the water solubility and isoelectric point of N‐CMC with different degrees of substitution were determined. FTIR and ¹H‐NMR data has confirmed that the substitution reaction occurred on the amino groups. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Thiolated chitosans: In vitro comparison of mucoadhesive properties

The aim of this study was to compare the mucoadhesive properties of thiolated chitosans with regard to their molecular mass and type of immobilized thiol ligand. Mediated by a carbodiimide, aromatic‐ and aliphatic‐thiol‐bearing compounds were covalently attached to low‐ and medium‐molecular‐mass chitosan. All synthesized conjugates displayed on average 320 ± 50 μmol of immobilized free thiol groups per gram of polymer. The rheological synergy was observed by the mixture of equal volumes of polymer with mucin solution. Because of the increase in viscosity of the conjugate/mucin mixture, the self‐crosslinking properties and the interaction of thiomers with the mucus layer could be confirmed. Further mucoadhesion of the chitosan conjugates was evaluated in vitro with the rotating cylinder method and tensile studies on excised porcine intestinal mucosa. The results show a significantly enhanced residence time (p < 0.05) on the mucosa of all thiolated chitosans compared to the unmodified polymer. Among all of the conjugates tested, the following rank order of mucoadhesion could be determined: Chitosan–thiobutylamidine > Chitosan–4‐mercaptobenzoic acid > Chitosan–glutathione > Chitosan–6‐mercaptonicotinic acid > Chitosan–N‐acetyl cysteine > Chitosan–thioglycolic acid > Unmodified chitosan. The charge, pK_a, and reactivity of the attached compounds were found to be important factors influencing the mucoadhesive potential of the polymer. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Structure and antimicrobial activity relationship of quaternary N‐alkyl chitosan derivatives against some plant pathogens

In the present work, quaternary chitosans as water‐soluble compounds were prepared based on three‐step process. Schiff bases were firstly synthesized by the reaction between the amino groups of chitosan with aliphatic aldehydes followed by a reduction with sodium borohydride (NaBH₄) to form N‐(alkyl) chitosans. N,N,N‐(dimethyl alkyl) chitosans were then obtained by a reaction of chitosan containing N‐butyl, N‐pentyl, N‐hexyl, N‐heptyl, and N‐octyl substituents with methyl iodide. The compounds were characterized using IR and NMR spectroscopy. Subsequent experiments were conducted to test their antimicrobial activities against the most economic plant pathogenic bacteria of crown gall disease Agrobacterium tumefaciens, soft mold disease Erwinia carotovora, fungi of grey mold Botrytis cinerea, root rot disease Fusarium oxysporum, and damping off disease Pythium debaryanum. Quaternary chitosans enhanced the antibacterial activity and N,N,N‐(dimethyl pentyl) chitosan was the most active one with Minimum Inhibitory Concentration (MIC) of 750 and 1225 mg/L against A. tumefaciens and E. carotovora, respectively. All quaternized chitosans gave stronger antifungal activities than chitosan where N,N,N‐(dimethyl pentyl) chitosan and N,N,N‐(dimethyl octyl) chitosan were significantly the highest in mycelial growth inhibiation against B. cinerea (EC₅₀ = 908 and 383 mg/L, respectively), F. oxysporum (EC₅₀ = 871 and 812 mg/L, respectively), and P. debaryanum (EC₅₀ = 624 and 440 mg/L, respectively). In addition, spore germination of B. cinerea and F. oxysporum was significantly affected with the compounds at the tested concentrations and the inhibition activity was increased with an increase in the chain length of the alkyl substituent. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

不同相对分子质量壳聚糖絮凝性能

壳聚糖作为天然高分子絮凝剂具有无毒、不存在2次污染、使用方便等优点;但生产和应用成本高,具有一定限制。而相对分子质量是壳聚糖的一个重要分子参数,不同相对分子质量的壳聚糖性质差异很大,研究了不同相对分子质量的壳聚糖对生活污水的絮凝性能,结果表明：高相对分子质量壳聚糖的絮凝效果较好,且随着壳聚糖用量的增加絮凝性能也随之增加,但是5×10^-6后絮凝下降,其在pH值为6.5时絮凝效果最佳。     

Preparation of O‐carboxymethyl‐N‐trimethyl chitosan chloride and flocculation of the wastewater in sugar refinery

A novel water soluble amphiphilic O‐ carboxymethyl‐N‐trimethyl Chitosan chloride (CMTMC) was synthesized. The structure of this material was characterized by Fourier transform infrared (FTIR) spectroscopy, ¹³C nuclear magnetic resonance (¹³C‐NMR) spectroscopy and X‐ray diffraction (XRD) techniques. The results showed that CMTMC had been successfully prepared. To determine the flocculation performance of the synthesized amphiphilic polymer, a comparison was made among Chitosan (CS), N‐trimethyl chitosan chloride (TMC), O‐carboxymethyl chitosan (CMC), and CMTMC on the turbidity and COD removal efficiency of 1% (v/v) wastewater in sugar refinery suspensions at pH 5.0, 7.0 and 9.0 at a dosage range of 0–8 mg/L. The results showed that the water soluble amphiphilic polymer CMTMC, which contains longer polymer anion and polymer cation, had the best performance not only in turbidity removal but also in COD removal on sugar refinery wastewater. The using of CMTMC as a flocculant to treat wastewater in sugar refinery was actually more effective than CS, CMC, and TMC. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis,characterization, and metal ions adsorption properties of chitosan–calixarenes (I)

Calixarene‐modified chitosans (CTS–CA‐I and CTS–CA‐II) were first synthesized by the reaction of chitosan (CTS‐NH₂) with 1,3‐bis‐chloroethoxyethoxy‐2,4‐dihydroxy‐p‐tert‐butylcalix[4]arene (CA‐I) or its benzoyl derivative (CA‐II). Their structures were characterized by infrared and X‐ray diffraction spectroscopy and scanning electron microscopy (SEM). The adsorption of Ni²⁺, Cd²⁺, Cu²⁺, Pd²⁺, Ag⁺, and Hg²⁺ by CTS–CA‐I and CTS–CA‐II was studied and the thermodynamic parameter of two calixarene‐modified chitosans toward Hg²⁺ was deduced. The adsorption properties of CTS–CA‐I and CTS–CA‐II were greatly varied compared with that CTS‐NH₂, especially with the adsorption capacity toward Ag⁺ and Hg²⁺, because of the presence of the calixarene moiety. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1139–1144, 2003     

Effects of hydrophilic/hydrophobic surfaces on polymer‐complexation kinetics

To establish hydrophilic/hydrophobic effects on polymer‐complexation kinetics, chitosan resins were prepared by radical copolymerization of methacryloyl‐modified chitosans with 2‐hydroxyethyl methacrylate and/or styrene monomers. The primary particles of the gelled copolymers in the suspensions were nicely solidified by basic coagulation bath to form globular beads. Degree of the hydrophilic/hydrophobic properties was controlled by the copolymerization ratio, and each ion‐adsorption kinetics was evaluated by batch method. The initial rate of adsorption in hydrophilic chitosans was higher than that in hydrophobic chitosans, which was attributed to less thickness of the boundary film. We quantitatively evaluated the rate‐determining steps by the initial‐rate analysis, in which the viscosity of the suspension contributes to the film‐diffusion kinetic resistance. The role of hydrophilic/hydrophobic properties of the resins is reasonably rationalized to the length of the boundary films by considering long‐range interactions between the ion and surface. Our results are robust evidence for the ion‐surface interactions. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46493.     

Synthesis of chemically modified chitosans with a higher fatty acid glycidyl and their adsorption abilities for anionic and cationic dyes

Novel chitosan‐based materials with a higher fatty acid glycidyl as the chemically modified agent were synthesized and the adsorption ability of the resulting polymers has been evaluated for typical anionic and cationic dyes. The successful modification was confirmed by the infrared spectroscopic measurements. As the degree of substitution was decreased, the adsorption ability of the chemically modified chitosans for anionic dyes at the higher dye concentration was increased, and the modified chitosans with a lower degree of substitution showed a higher adsorption ability than that of an activated carbon at the higher dye concentration. For cationic dyes, the chemically modified chitosan showed a good adsorption power, especially when the adsorption power was evaluated by the flow methods. The improved adsorption ability of a chemically modified chitosan material was also confirmed by comparing it with that of a crosslinked chitosan material. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2423–2428, 2005     

Molecular weight effect on antimicrobial activity of chitosan treated cotton fabrics

The effect of the molecular weight of chitosan on antimicrobial activity was investigated using three chitosans of different molecular weights [1800 (water soluble), 100,000, and 210,000] and similar degrees of deacetylation (86–89%). Cotton fabrics were treated with chitosan by the pad–dry–cure method. The molecular weight dependence of the antimicrobial activity of chitosan was more pronounced at a low treatment concentration. Chitosans with molecular weight of 100,000 and 210,000 effectively inhibited Staphylococcus aureus at a 0.5% treatment concentration. Chitosan with a molecular weight of 1800 was effective against S. aureus at a 1.0% treatment concentration. Escherichia coli was effectively inhibited by chitosan with a molecular weight of 210,000 at a 0.3% treatment concentration and by chitosans with a molecular weight of 1800 and 100,000 at a 1.0% treatment concentration. Proteus vulgaris was effectively inhibited by chitosans with molecular weight of 100,000 and 210,000 at a 0.3% treatment concentration and by chitosan with a molecular weight of 1800 at a 0.5% treatment concentration. None of the chitosans significantly inhibited Klebsiella pneumoniae and Pseudomonas aeruginosa below a 1.0% treatment concentration. Chitosans with high molecular weights were more effective in inhibiting bacterial growth than chitosans with low molecular weights. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2495–2501, 2001     

Synthesis,characterization, flocculation,and rheological characteristics of hydrolyzed and unhydrolyzed polyacrylamide‐grafted poly(vinyl alcohol)

Graft copolymers of poly(vinyl alcohol) and polyacrylamide (PVA‐g‐PAM) were synthesized using a ceric ion–induced solution polymerization technique at 28°C. Three grades of graft copolymers were synthesized with varying acrylamide concentrations. Three grades of hydrolyzed products of PVA‐g‐PAM were synthesized with varying concentrations of sodium hydroxide solution. Hydrolyzed and unhydrolyzed PVA‐g‐PAM were characterized by viscometry, X‐ray diffractometry, infrared spectroscopy, and thermal analysis. Rheological investigation was also carried out on the aqueous solutions of various samples. The flocculation characteristics of various materials were investigated by the use of jar and settling tests in 0.25 and 5 wt %, respectively, using kaolin and iron ore suspensions. Among the series of graft copolymers, the one with fewest but longest PAM chains showed superior performance. The flocculation characteristics of the best‐performing graft copolymer were compared with those of various commercially available flocculants in the two suspensions under investigation. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2109–2122, 2006     

Influence of chitosan characteristics on coagulation and flocculation of organic suspensions

Several samples of chitosan with different degrees of deacetylation and of different molecular weights were tested for the coagulation–flocculation of organic suspensions. Organic suspensions were prepared by mixing mushroom powder with tap water. Experiments were carried out at pH 5, pH 7, and pH 9. Because decreasing the pH reduced the amount of chitosan required to reach the required turbidity, at pH 9, a high concentration of chitosan was required to achieve the required treatment levels, whereas the difference was less significant between pH 7 and pH 5 (the required concentration of chitosan was halved). Though viscosity, correlated to the molecular weight of chitosan, affected treatment performance, its influence on the efficiency of coagulation–flocculation could be substantially reduced by slightly increasing the concentration of the polymer. This is of importance in the processing of industrial effluents: the aging of a chitosan solution, which may cause partial depolymerization, and loss of viscosity, will have a limited impact on process efficiency. The degree of deacetylation also has a limited effect on treatment performance, especially when the degree of deacetylation exceeds 90%. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2070–2079, 2005     

Synthesis and rheological behavior of a novel N‐sulfonate ampholyte chitosan

Modified chitosan derivatives with different degrees of substitution varying from 0.17 to 0.96 were synthesized by the heterogeneous reaction of chitosan with 3‐chloro‐2‐hydroxy propanesulfate in a neutral aqueous solution. The modified chitosans with a degree of substitution higher than 0.36 were soluble in water, whatsoever the pH. The structures of the polymers were characterized by Fourier transform infrared and ¹H‐nuclear magnetic resonance spectroscopies. The potentiometric titration revealed that the modified chitosan had an isoelectric point at around pH = 5.7, and its rheological behaviors in aqueous solution were studied under different conditions. The results showed that the modified chitosan had typical polyampholyte characteristics, which exhibited polyelectrolyte effect at pH = 1.7 or 13 and antipolyelectrolyte effect at pH = 8. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009