Development of chitosan-alginate based biosorbent for the removal of p-chlorophenol from aqueous medium

Removal of p-chlorophenol (pCP) from synthetic aqueous solutions was studied through adsorption on a biosorbent developed from chitosan (CS) and sodium alginate (SA), the natural cationic and anionic polysaccharides, respectively. Chitosan-coated sodium alginate beads were prepared and treated with calcium chloride solution in order to improve the stability as well as hydrophobic character. The resulting beads (CS/CA) were characterized using FTIR spectra, scanning electron microscopy (SEM), and BET surface analysis. The efficiency of this biosorbent in removing pCP from aqueous medium was studied under batch equilibrium and dynamic column flow experimental conditions. The binding capacity of the biosorbent was studied as a function of initial pH, contact time, initial concentration of adsorbate and amount of biomass. The data were fitted to pseudo-first-order, pseudo-second-order, and Weber–Morris models and found that the adsorption process followed pseudo-first-order kinetics. Further, the equilibrium data were fitted to Freundlich, Langmiur, and Dubinin–Radushkevich (D–R) adsorption isotherms and the isotherm constants were evaluated for adsorption of pCP. The maximum monolayer adsorption capacity of CS/CA beads was found to be 127 mg g^?1. Column flow results were used to generate breakthrough curves. The experimental results suggested that the chitosan–calcium alginate blended biosorbent was effective for the removal of pCP from aqueous medium.     

软水中EPS对铜管/磷酸盐体系溶解性铜释放的影响

以海藻酸钠模拟水体中的细胞外高聚物(EPS)，研究软水体系中海藻酸钠对铜管／磷酸盐缓蚀行为的影响，结果表明：低浓度海藻酸钠能明显提高软水一铜管一磷酸盐体系中溶解性铜的释放，从而降低磷酸盐对铜管的缓蚀效果，而且从新管释放的溶解性铜远高于老化6个月、12个月和10年的铜管，释放溶解铜的顺序为Cnew＞C6m＞C12m＞C10y；随着海藻酸钠含量的增加，溶解性铜的释放浓度降低，但仍高于对照试验．在低pH条件下，海藻酸钠对溶解性铜的释放影响显著，从新管释放的溶解性铜浓度低于老化6个月、12个月和10年的铜管，这可能是由于不同老化时间的铜管其腐蚀表面的组成不同，水质pH值明显影响这些腐蚀副产物的溶解性铜释放；在不同停留时间内，随着水体组成的变化，溶解性铜的释放浓度不断发生变化，表明海藻酸钠与铜离子形成的络合物影响磷酸与铜的相互作用，从而影响磷酸盐对铜管的缓蚀效果．     

壳聚糖/膨润土复合絮凝剂处理染料废水的研究

利用壳聚糖/钠基膨润土复合絮凝剂对活性艳红X3B等11种染料模拟废水及实际印染废水进行絮凝脱色处理。考察了复合絮凝剂投加量、pH值、搅拌速率、搅拌时间等因素对模拟染料废水絮凝脱色的影响。结果表明,在染料浓度为100 mg.L-1,pH为5的条件下,复合絮凝剂投加量为1.25 g.L-1时,3种质量比的复合絮凝剂对活性艳红X3B的脱色率分别达到75%、90%和97%以上;质量比为1∶10的壳聚糖/钠基膨润土复合絮凝剂,对其它活性、还原性、分散性、水溶性等8种印染厂常用染料也具有很好的絮凝脱色作用,脱色率均可达94%以上。对印染废水处理厂进水口废水和经过A/O处理后废水的色度去除率和COD去除率分别可以达到81.05%、83.74%和53.21%、41.22%,具有一定的应用前景。     

Efficient oxidation of sulfides into sulfoxides catalyzed by a chitosan–Schiff base complex of Cu(II) supported on supramagnetic Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles

Sulfoxides are versatile synthetic intermediates for the preparation of biological products. Therefore, there is a need for efficient methods to oxidize sulfides into sulfoxides. Such oxidation may be catalyzed by magnetic nanocatalysts due to their good stability, easy synthesis, high surface area, low toxicity and easy separation by magnetic forces. Here we prepared a nanocatalyst by immobilization of the chitosan–Schiff base complex on supramagnetic Fe₃O₄ nanoparticles. The chitosan–Schiff base complex has been previously prepared by functionalization of chitosan with 5-bromosalicylaldehyde and metalation with copper(II) acetate. The catalyst was characterized by Fourier transform infrared, powder X-ray diffraction, transmission electron microscope, scanning electron microscopy, energy-dispersive X-ray spectroscopy and thermogravimetric analysis. Results show that the Fe₃O₄ nanoparticles and nanocatalyst were spherical in shape with an average size of 20 nm. Upon the covalently anchoring of chitosan–Schiff base Cu complex on the magnetic Fe₃O₄ nanoparticles, the average size increased to 60 nm. The prepared Fe₃O₄–chitosan–Schiff base Cu complex catalyzed very efficiently the oxidation of sulfides to sulfoxides with 100 % selectivity in all cases under green reaction conditions and excellent yields. Additionally, ease of recovery and reusability up to four cycles without noticeable loss of catalytic activity make the present protocol beneficial from industrial and environmental viewpoint.     

Biopolymer-supported TiO2 as a sustainable photocatalyst for wastewater treatment: a review

The rising water pollution by pesticides, pharmaceuticals and dyes is a major health issue calling for advanced remediation methods such as photocatalysis with titanium dioxide (TiO₂), yet the use of TiO₂ displays issues of aggregation, mass loss, recovery, and reusability. These issues have been recently solved by synthesizing biopolymer-supported photocatalysts using cheap, biodegradable and safe biopolymers such as chitosan, alginate, cellulose, cyclodextrin, guar gum and starch. Here we review biopolymer-supported TiO₂ photocatalysts for the removal of organic compounds, with focus on preparation methods, photo and chemical stability, reusability, and adsorptive capacity. We discuss applications of immobilized photocatalysts at the industrial scale.

     

钾改性蒙脱石磁性微球对铯的吸附性能

本研究以钙基蒙脱石(Ca-MMT)为原料,通过K+作用制得改性蒙脱石粉(K-MMT),经海藻酸钠交联作用,将改性蒙脱石与永磁体(BaFe12O19)结合,制成钾改性蒙脱石磁性微球(KMBC).对比了 Ca-MMT、K-MMT、KMBC对Cs+的吸附差异,并通过SEM-EDS、FTIR、XRD、XPS分析了 K-MMT的...     

Large-scale synthesis and antibacterial activity of fungal-derived silver nanoparticles

There is a demand for environmentally friendly processes to synthesize nanoparticles. Here, we synthesized silver nanoparticles using encapsulated biomass beads of Phoma exigua var. exigua. Nanoparticles were characterized by nanoparticle tracking and analysis (NTA), Fourier-transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy and zeta potential. Results of NTA show that nanoparticle size was homogenous. Concerning nanoparticle stability, zeta potential decreased with batch number. Silver nanoparticles exhibited an antibacterial activity against Escherichia coli and Staphylococcus aureus. Overall, the encapsulation of fungal biomass by calcium alginate for the batch synthesis of silver nanoparticles was easy, cost-effective, eco-friendly and suitable for the large-scale synthesis of silver nanoparticles. We have also demonstrated the reusability of the fungal biomass during biosynthesis of silver nanoparticles using the sodium alginate encapsulation method.     

蒙脱石颗粒吸附剂的制备

利用PVA为包埋剂、硼酸溶液为交联剂制备蒙脱石颗粒吸附剂,确定了适宜的包埋条件,即PVA浓度为10%、海藻酸钠浓度为0.2%、包埋量为1:1和交联时间为24 h。在该条件下制备的颗粒吸附剂,强度较大,对低浓度氨氮废水去除效果好于粉末状蒙脱石吸附剂,为粉末状吸附剂提供一种新型有效的成型方法。     

Fe3O4@SA/Ce微球的表征及对染料的吸附特性

以天然高分子化合物海藻酸钠(sodium alginate,SA)为骨架,结合磁性Fe₃O₄和稀土铈离子Ce(Ⅲ)通过溶液反应制备出一种新型的磁性海藻酸铈复合微球(Fe₃O₄@SA;Ce).采用X射线衍射(XRD)、孔结构比表面积分析(BET)、扫描电子显微镜(SEM)、红外光谱(FT-IR)及振动样品强磁计(VSM)对Fe₃O₄@SA;Ce的结构进行了表征,并以直接桃红12B(direct red 12B,DR 12B)和直接橙S(direct orange S,DO S)两种染料为吸附对象,探讨了Fe₃O₄@SA;Ce的吸附剂性能、吸附动力学和热力学.结果表明,Fe₃O₄@SA;Ce对室温下自然pH染料溶液中DR 12B和DO S均表现出良好的吸附效果,吸附量分别可达464 mg·g^-1和730 mg·g^-1.在不同温度下(298、313、328 K),Fe₃O₄@SA;Ce对DR 12B和DO S的吸附过程均可用拟二级吸附动力学方程准确描述.通过等温吸附研究,发现Fe₃O₄@SA;Ce对两种染料的等温吸附较好地符合Freundlich模型.各种表征结果表明,SA与Ce(Ⅲ)和Fe₃O₄交联反应后生成的Fe₃O₄@SA;Ce凝胶球表面有大量深浅不一的褶皱沟纹,形貌发生了显著变化.作为一种绿色环保、制备方法简单、可高效吸附的磁性高分子复合吸附剂,Fe₃O₄@SA;Ce对高浓度染料具有很好的吸附效果,期望能够在染料废水处理中得到广泛应用.     

Maximum uptakes of cadmium on free and immobilised bacteria and actinomycetes cells

Studies of adsorption of cadmium by free bacterial and free actinomycete cells, alginate beads and immobilised bacterial or actinomycete cells in alginate beads were performed in ultrapure water. The immobilisation in alginate beads allows the survival of the microorganisms in non-ideal conditions. Here, we found the following affinity for the cadmium ion: R25 free cells<alginate beads<R25 immobilised cells<ZAN 044 immobilised cells<ZAN 044 free cells, obtained with the b Langmuir parameter. The maximum uptakes gave the series: ZAN 044 free cells<ZAN 044 immobilised cells<R25 free cells<alginate beads<R25 immobilised cells.     

Oleoyl-carboxymethyl chitosan as a new carrier agent for the rotenone pesticide

Rotenone is an active ingredient that has been widely used as pesticide. However, rotenone is poorly soluble in water. Therefore, a water-soluble carrier is needed. Here, we synthesised, characterised and applied oleoyl-carboxymethyl chitosan for the first time as a carrier agent for rotenone. Oleoyl-carboxymethyl chitosan is soluble in acidic, neutral and basic media. The critical micelle concentration of oleoyl-carboxymethyl chitosan is 0.096 mg/mL. Oleoyl-carboxymethyl chitosan formed self-aggregates and exhibited spherical shape with the values of 35.5–66.4 nm. We studied the encapsulation efficiency and loading capacity of oleoyl-carboxymethyl chitosan micelles with different weight ratios of oleoyl-carboxymethyl chitosan to rotenone. We found an encapsulation efficiency of 97 % and a loading capacity of 0.97 % for oleoyl-carboxymethyl chitosan/rotenone 100:1 w/w. Oleoyl-carboxymethyl chitosan released 96.00 % of the rotenone loaded within 50 h. Overall, our findings show the feasibility of oleoyl-carboxymethyl chitosan as a novel water-solubilising agent for pesticide formulations.     

Calcium alginate accelerates elimination of environmental lead in preschool children

Environmental lead poses a serious threat for public health, particularly, for children. The use of substances with metal-binding properties, such as natural alginates, may be a potentially effective method for elimination of toxic metal ions from human body. In present study, effect of calcium alginate isolated from brown algae on distribution of the lead ions in preschool children was investigated. In the beginning of the study, lead concentration in urine, feces, and hair was determined. Then these children were administered a dietary supplement containing calcium alginate for four weeks. The results showed that all children participated in the study had a high baseline median lead level in urine (1.1 µg/L), feces (4.6 µg/g), and hair (5.0 µg/g). Administration of calcium alginate resulted in twofold increase of the urine lead level within two weeks from the start of the treatment. At the end of alginate administration, significant decrease of lead concentration in hair was registered. These results suggest that calcium alginate can potentially prevent accumulation of the lead ions in the body and may be used as an active agent for elimination of this toxic metal from human body.     

壳聚糖对菠菜中毒死蜱和乐果的降解作用（Effects of Spraying Chitosan on Degradation of Chlorpyrifos and Dimethoate Residues in Spinach）

在露地栽培条件下,研究了叶面喷施壳聚糖水溶液对菠菜中毒死蜱和乐果的降解作用.结果表明,叶面喷施不同浓度的壳聚糖(50、100、200、400mg·L-1)可有效降低菠菜中毒死蜱和乐果残留量,其中较低浓度壳聚糖能更有效地降低菠菜中毒死蜱、乐果的残留量.50mg·L-1壳聚糖使菠菜中毒死蜱残留量较对照降低40.2%,安全间隔期缩短2.07d;100mg·L-1壳聚糖使菠菜中乐果残留量较对照降低46.9%,安全间隔期缩短0.5d.壳聚糖作为一种有机磷农药降解剂应用于蔬菜生产是可行的.     

Removal of clofibric acid from aqueous solution by polyethylenimine-modified chitosan beads

Polyethylenimine （PEI）-modified chitosan was prepared and used to remove clofibric acid （CA） from aqueous solution. PEI was chemically grafted on the porous chitosan through a crosslinking reaction, and the effects of PEI concentration and reaction time in the preparation on the adsorption of clofibric acid were optimized. Scanning electron microscopy （SEM） showed that PEI macromolecules were uniformly grafted on the porous chitosan, and the analysis of pore size distribution indicated that more mesopores were formed due to the crosslinking of PEI molecules in the macropores of chitosan. The PEI-modified chitosan had fast adsorption for CA within the initial 5 h, while this adsorbent exhibited an adsorption capacity of 349 mg· g^-1 for CA at pH 5.0 according to the Langmuir fitting, higher than 213 mg· g^-1 on the porous chitosan. The CA adsorption on the PEI- modified chitosan was pH-dependent, and the maximum adsorption was achieved at pH 4.0. Based on the surface charge analysis and comparison of different pharmaceu- ticals adsorption, electrostatic interaction dominated the sorption of CA on the PEI-modified chitosan. The PEI- modified chitosan has a potential application for the removal of some anionic rnicropollutants from water or wastewater.     

壳聚糖改性膨润土处理焦化废水的实验研究

焦化废水是煤制焦炭、煤气净化及焦化产品回收过程中产生的废水,其成分复杂多变,属于难处理的工业废水。利用壳聚糖对膨润土进行改性,制备了壳聚糖改性膨润土,并应用于焦化废水的处理,并对影响处理效果的工艺参数进行了优化,结果表明：在pH=8.6,投加量为10g·mL-1,搅拌时间为30min,离心时间为12min条件下,改性膨润土对焦化废水CODcr的去除率达到82.5%以上,处理效果明显优于原土和壳聚糖。此外,通过对原土和壳聚糖改性膨润土进行的比表面积和扫描电镜等表征测定分析可知,壳聚糖的加入并没有改变膨润土的基本框架,只是增大了膨润土的比表面积,从而提高吸附性能。     

The use of chitosan of shrimp Penaeus sp. as cadmium adsorbent

Cadmium (Cd) is one of the heavy metals which contaminate the environment including water, air, and soil. At low concentrations, Cd produces adverse effects in aquatic organisms. An effort to reduce the level of Cd was conducted by removing the metal with chitosan. The aim of this study was to study the adsorption of Cd by using chitosan isolated from the shrimp Penaeus sp. as a function of stirring duration and chitosan concentration in aqueous solution. In this study, chitin was isolated by using NaOH 3% and HCl 1.25 N, adding NaOH 50% for the transformation of chitin to chitosan. For the adsorption test, chitosan was added to Cd solutions at concentrations of 0.2, 0.4, or 0.6 g per 10 ml Cd(NO₃)², stirring the solution for 5, 10, or 15 min, respectively. The results showed that the yield of isolated chitosan was 56% of crude prawn shell. The optimum concentration of chitosan was 0.6 g/10 ml with a stirring duration 10 min reducing Cd concentration by 91.7%.     

壳聚糖絮凝剂对聚合氯化铝的助凝作用

以壳聚糖絮凝剂作为聚合氯化铝(PAC)的助凝剂,絮凝处理颐和园昆明湖湖水,考察了PAC在壳聚糖助凝作用下对浊度和有机物的去除效果,以及水中残留铝浓度的变化．结果表明,壳聚糖对PAC的助凝作用显著,PAC中加入壳聚糖絮凝剂后,浊度和有机物去除率均明显提高．     

壳聚糖辅助下玉米修复铅污染土壤能力的研究

为了研究壳聚糖辅助下玉米(ZeamaysL.)对铅污染土壤的修复能力,采用L9(34)正交试验进行研究,考虑了4因素3水平,4因素为土壤铅含量、壳聚糖含量、壳聚糖溶液pH值以及加入壳聚糖后的提取时间.研究结果表明,加入壳聚糖会造成玉米生长停滞,甚至死苗,原因在于壳聚糖属于天然高分子有机物,会造成土壤板结,阻碍植物吸收水分,同时壳聚糖将土壤中的大量重金属溶出,造成玉米重金属中毒.加入壳聚糖后,玉米对铅的吸收较对照结果有很大提高,壳聚糖能够促进铅元素从土壤向植物体内转移,但壳聚糖促进铅元素从玉米地下部分向地上部分转移的能力较弱;综合壳聚糖的促进效果,在土壤铅含量为1.8g·kg-1,壳聚糖含量为5mmol·kg-1(土),壳聚糖溶液pH值为4.5,提取时间为7天的条件下,有利于促进铅在玉米地上部分的吸收.     

Solvent-free mechanochemical mild oxidation method to enhance adsorption properties of chitosan

• Solvent-free chitosan oxidation is obtained by rapid mechanochemical reaction. • Different oxidants induce very diverse physicochemical changes on chitosan. • Oxidized chitosan with persulfate or percarbonate has improved adsorption capacity. • Uptake on oxidized chitosan with persulfate is 125-fold faster than on pristine one. Oxidation has been profitably utilized to improve some properties of chitosan. However, only solvent-based oxidation procedures have been proposed so far, which are hardly feasible at industrial scale in an economic way because of product recovery cost. In this study, a solvent-free, rapid, and effective oxidation method is proposed. It is based on direct solid-state reaction between chitosan and oxidant powder in a mechanochemical reactor. Results prove that by short high energy ball milling (<3 h) it is possible to achieve diverse physicochemical modifications employing different reagents. Apart from polysaccharidic chain shortening, persulfate provokes high amorphization and induces formation of ketonic groups; percarbonate heightens deacetylation degree, preserving in part crystallinity; calcium peroxide merely deprotonates amino groups and increases amorphization degree. Adsorption tests with the azo-dye reactive red 2 show that adsorption capacity of chitosan co-milled with persulfate (974 mg/g milled product), which is the best performing adsorbent, is twice that of pristine chitosan, while adsorption rate is outstandingly boosted (125 times).     

壳聚糖负载膨润土处理高浊度废水的效果

以天然膨润土为原料,壳聚糖为改性剂,采用微波改性技术制备了壳聚糖负载膨润土,应用于高浊度废水的处理.通过正交试验确定了废水处理工艺各种影响因素的最佳条件.比较了负载土、原土、壳聚糖的处理效果,结果表明:负载土对高浊度废水的去浊效果明显好于原土、壳聚糖;对于浊度为9250～9480 NTU的废水,经30 min自由沉降后,在投土量为4.0 g·L~(-1)、投土粒度为0.150 mm、搅拌速度为100 r·min~(-1)、搅拌时间为10 min的条件下,废水剩余浊度为6.0～7.0 NTU,浊度去除率高达99.9%.出水水质满足<再生水作循环冷却水水质>的水质要求.