Removal of chromium (VI) from aqueous solutions using quaternized chitosan microspheres

In this study, quaternized chitosan microspheres (QCMS) were prepared and its Cr(VI) removal potential was investigated. Batch experiments were conducted to examine kinetics, adsorption isotherm, pH effect, and thermodynamic parameters. Equilibrium was attained within 50 min and maximum removal of 97.34% was achieved under the optimum conditions at pH 5. Adsorption data for Cr (VI) uptake by the QCMS were analyzed according to Langmuir, Freundlich, and Temkin adsorption models. The maximum uptake of Cr(VI) was 39.1 mg·g^-1. Thermodynamic parameters for the adsorption system were determinated at 293 K, 303 K, 313 K and 323 K. (ΔH°=16.08 kJ·mol^-1;ΔG°=-5.84 to -8.08 kJ·mol^-1 and ΔS°=74.81 J·K^-1·mol^-1). So the positive values of both ΔH° and ΔS° suggest an endothermic reaction and increase in randomness at the solid-liquid interface during the adsorption.ΔG° values obtainedwere negative indicating a spontaneous adsorption process. The kinetic process was described by a pseudo-second-order rate equation very well. The results of the present study indicated that the QCMS could be considered as a potential adsorbent for Cr (VI) in aqueous solutions.     

Effective and selective adsorption of uranyl ions by porous polyethylenimine-functionalized carboxylated chitosan/oxidized activated charcoal composite

Composite materials have elicited much interest because of their superior performance in the removal of toxic and radioactive uranyl ions from aqueous solutions.With polyethyleneimine as a functional group,carboxylated chitosan as a matrix,and oxidizing activated carbon as a nanofiller,this study synthesized a novel environment-friendly polyethylenimine-functionalized carboxylated chitosan/oxidized activated charcoal(PCO)biocomposite with a unique three-dimensional porous structure.PCO was synthesized through an easy chemical cross-linking method.Detailed characterization certified the formation of the unique three-dimensional porous structure.The obtained PCO was used to remove uranyl ions from an aqueous solution,demonstrating the maximum adsorption capacity of 450 mg·g^?1.The adsorption capacity of PCO decreased by less than 7.51%after five adsorption-desorption cycles.PCO exhibited good adsorption selectivity(K_d=3.45×10⁴ mL·g^?1)for uranyl ions.The adsorption mechanism of PCO was also discussed.The material showed good potential for application in the treatment of wastewater containing uranyl ions.     

Removal of Reactive Red 198 from aqueous solution by combined method multi-walled carbon nanotubes and zero-valent iron:Equilibrium,kinetics, and thermodynamic

Dyes often include toxic,carcinogenic compounds and are harmful to humans' health.Therefore,removal of dyes from textile industry wastewater is essential.The present study aimed to evaluate the efficiency of the combination of zero valent iron(ZVI) powder and multi-walled carbon nanotubes(MWCNTs) in the removal of Reactive Red 198(RR198) dye from aqueous solution.This applied research was performed in a batch system in the laboratory scale.This study investigated the effect of various factors influencing dye removal,including contact time,p H,adsorbent dose,iron powder dose,initial dye concentration,and temperature.The equilibrium adsorption data were analyzed using three common adsorption models:Langmuir,Freundlich and Temkin.Besides,kinetic and thermodynamic parameters were used to establish the adsorption mechanism.The results showed,in pH =3,contact time = 100 min,ZVI dose = 5000 mg·L~(-1),and MWCNTs dose = 600 mg·L~(-1)in 100 mg·L~(-1)dye concentration,the adsorption efficiency increased to 99.16%.Also,adsorption kinetics was best described by the pseudo-second-order model.Equilibrium data fitted well with the Freundlich isotherm(R2= 0.99).The negative values of ΔG0and the positive value of ΔH0(91.76) indicate that the RR198 adsorption process is spontaneous and endothermic.According to the results,the combination of MWCNTs and ZVI was highly efficient in the removal of azo dyes.     

乙二胺丙酰化交联壳聚糖微球对甲基橙的吸附性能

通过丙烯酰化交联壳聚糖微球（AGCS）上的丙烯酰基团与乙二胺的Michael加成反应，制备乙二胺丙酰化交联壳聚糖微球（EAGCS）。分别采用傅里叶变换红外光谱（FT-IR）、X射线光电子能谱（XPS）和X射线衍射（XRD）表征了EAGCS的结构，利用激光粒度分析仪进行了粒径分布分析，考察了甲基橙（MO）溶液pH、温度、浓度和EAGCS用量对EAGCS吸附性能的影响。结果表明：EAGCS为球形，微球的体积平均粒径为57.4 μm，粒径分布系数1.53；在最佳条件下，EAGCS的吸附去除率为99.6%，吸附容量可达545.40 mg·g^-1，吸附过程属于自发放热过程，吸附动力学符合二级动力学，吸附过程可采用Langmuir和Freundlich等温吸附模型来描述。     

Preparation of a porous,magnetic, quaternary chitosan salt by preadsorption and desorption for azo dye adsorption from water

A porous magnetic quaternary chitosan salt (pre‐CS/EPTAC/Fe₃O₄) was successfully prepared via a kind of novel method of preadsorption and desorption. The physicochemical properties of pre‐CS/EPTAC/Fe₃O₄ were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and vibrating sample magnetometry. The adsorption of pre‐CS/EPTAC/Fe₃O₄ for methyl orange (MO) showed much higher dye uptakes compared with Npre‐CS/EPTAC/Fe₃O₄ without the preadsorption and desorption of MO, and the maximum adsorption capability for MO was 486.1 mg/g. Adsorption isotherms and adsorption kinetics were well fitted by the Freundlich isotherm model and the pseudo‐second order model, respectively. Thermodynamic parameters, such as the standard free energy change, enthalpy change, and entropy change, were also calculated; this indicated that the adsorption was spontaneous and exothermic. The introduction of MO preadsorption and desorption into the process of preparation improved not only the adsorption of MO but also the adsorption of acid red 1 and orange G. Furthermore, pre‐CS/EPTAC/Fe₃O₄ particles could be easily regenerated and remained almost constant (98.5%) for six cycles of adsorption and desorption. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43448     

季铵盐链长及用量对CnTA+/蒙脱石纳米复合物吸附PAEs的影响

用具有相同结构但不同烷基碳链长度的系列季铵盐制得C_nTA⁺/蒙脱石纳米复合物,并对水溶液中邻苯二甲酸酯进行吸附实验。探讨了季铵盐烷基碳链链长和用量对制得的C_nTA⁺/蒙脱石纳米复合物吸附水溶液中PAEs效果的影响。结果表明:C_nTA⁺/蒙脱石纳米复合物能有效地吸附溶液中的PAEs,季铵盐烷基碳链链长及用量均对C_nTA⁺/蒙脱石纳米复合物的吸附效果产生影响。当季铵盐用量较低时,随着季铵盐烷基链长的增加,PAEs的吸附去除率增加;增大季铵盐用量,随着季铵盐烷基链长的增加,PAEs的吸附去除率先增大后减小。     

新型壳聚糖/锆复合球的制备及硼吸附性能

通过氧氯化锆与壳聚糖的配位反应以及Zr （OH）4在壳聚糖内的原位沉淀,制备了一种新型壳聚糖-锆复合球（CTS-Zr）并用于硼的吸附分离。采用扫描电子显微镜（SEM）和傅里叶红外光谱（FTIR）对CTS-Zr进行了表征,系统考察了溶液pH、硼初始浓度、接触时间、温度及共存阴离子Cl^-、NO₃^-和SO₄^2-对CTS-Zr吸附性能的影响。结果表明：pH=2～7时,CTS-Zr对硼的吸附效率较高;吸附平衡行为符合Langmuir等温吸附模型;pH=7时,最大吸附量计算值为21.1 mg·g^-1;吸附动力学符合准二级动力学模型;常见的共存阴离子对硼的吸附影响很小;吸附热力学研究表明,CTS-Zr对硼的吸附过程为放热的非自发过程;使用pH=12的NaOH水溶液,对吸附剂CTS-Zr进行了洗脱,洗脱效率为96.3%,且经过3次吸附-解吸循环后,CTS-Zr的吸附效率没有明显降低。     

Adsorption removal of o-nitrophenol and p-nitrophenol from wastewater by metal–organic framework Cr-BDC

In the present paper, a metal–organic framework Cr-BDC was prepared and used as adsorbent for adsorption of o-nitrophenol(ONP) and p-nitrophenol(PNP) from aqueous solutions. Cr-BDC was characterized by scanning electron microscopy, transmission electron microscope, X-ray diffraction and BET methods. The results indicate that Cr-BDC gets a very large specific surface area of 4128 m~2·g~(-1)and pore sizes are concentrated in 1 nm, which is a benefit for using for wastewater treatment. The influences of the adsorption conditions, such as temperature,solution concentration, adsorption time and reusability on adsorption performance were investigated. Cr-BDC exhibited an encouraging uptake capacity of 310.0 mg·g~(-1)for ONP, and adsorption capacity of Cr-BDC for ONP is significantly higher than that for PNP under suitable adsorption conditions. The characterizations of adsorption process were examined with the Lagergren pseudo-first-order, the pseudo-second-order kinetic model, and the intra-particular diffusion model. Kinetics experiments indicated that the pseudo-second-order model displayed the best correlation with adsorption kinetics data. Furthermore, our adsorption equilibrium data could be better described by the Freundlich equation. The results indicate that the as-prepared Cr-BDC is promising for use as an effective and economical adsorbent for ONP removal.     

交联氧化铝-壳聚糖新杂化吸附剂的制备及去除废水中Cu(Ⅱ)(英文)

A novel biosorbent was developed by coating chitosan,a naturally and abundantly available biopolymer,on to activated alumina based on oil shale ash via crosslinking.The adsorbent was characterized by various techniques,such as Fourier transform infrared spectroscopy,scanning electron microscopy,thermogravimetric-differential thermal analysis,and X-ray photoelectron spectroscope.Batch isothermal equilibrium adsorption experiments were condcted to evaluate the adsorbent for the removal of Cu(Ⅱ) from wastewater.The effect of pH and agitation time on the adsorption capacity was also investigated,indicating that the optimum pH was 6.0.The equilibrium adsorp-tion data were correlated with Langmuir and Freundlich models.The maximum monolayer adsorption capacity of chitosan coated alumina sorbent as obtained from Langmuir adsorption isotherm was found to be 315.46 mg·g-1 for Cu(Ⅱ).The adsorbent loaded with Cu(Ⅱ) was readily regenerated using 0.1 mol?L?1 sodium hydroxide solution.All these indicated that chitosan coated alumina adsorbent not only have high adsorption activity,but also had good stability in the wastewater treatment process.     

Adsorption of Methyl Orange on Magnetically Separable Mesoporous Titania Nanocomposite☆

The adsorption of mesoporous Fe3O4–SiO2–TiO2 (MFST), which can be separated easily from solution by a mag-net, for the removal of methyl orange (MO) was investigated. The nitrogen adsorption–desorption...     

Synthesis of graphene oxide nanoribbons/chitosan composite membranes for the removal of uranium from aqueous solutions

In this study, a graphene oxide nanoribbons/chitosan (GONRs/CTS) composite membrane was successfully prepared by encapsulating CTS into GONRs, which were unzipped from multi-walled carbon nanotubes. The GONRs/CTS composite membrane so prepared was characterized using scanning electron microscopy, X-Ray diffraction and Fourier transform infrared spectroscopy. The effects of the experimental conditions such as the pH (2‒7), adsorbent dosage (10‒50 mg), experimental time (5 min–32 h), uranium concentration (25‒300 mg∙L⁻¹), experimental temperature (298 K‒328 K) on the adsorption properties of the composite membrane for the removal of U(VI) were investigated. The results showed that the U(VI) adsorption process of the GONRs/CTS composite membrane was pH-dependent, rapid, spontaneous and endothermic. The adsorption process followed the pseudo-secondary kinetics and Langmuir models. The maximum U(VI) adsorption capacity of the GONRs/CTS composite membrane was calculated to be 320 mg∙g⁻¹. Hence, the GONRs/CTS composite membrane prepared in this study was found to be suitable for separating and recovering uranium from wastewater.     

污泥含炭吸附剂的制备及其吸附模拟烟气中汞蒸汽的应用(英文)

The carbonaceous adsorbent was prepared from mixtures of dewatered sludge and sawdust with enhanced ZnCl2 chemical activation.Characteristics of the adsorbent were studied using scanning electron microscope(SEM) ,Fourier transform infrared spectroscopy(FT-IR) ,and adsorption of nitrogen.The surface analysis showed that the carbonaceous adsorbent had good specific surface and porosity(394 m 2 ·g-1of BET surface,0.12 and 0.10 ml·g-1of microporous and mesoporous volume,respectively) .The oxygen functional groups such as OH,C O and C O were found on the surface by FTIR and XPS(X-ray photoelectron spectroscopy) .The adsorption of elemental mercury(Hg0) on the carbonaceous adsorbent was studied in a fixed bed reactor.The dynamic adsorption capacity of carbonaceous adsorbent increased with influent mercury concentration,from 23.6μg·g-1at 12.58μg·m-3to 87.9μg·g-1at 72.50μg·m-3,and decreased as the adsorption temperature increased,from 246 μg·g-1 at 25°C to 61.3μg·g-1 at 140°C,when dry nitrogen was used as the carrier gas.The carbonaceous adsorbent presented higher dynamic adsorption capacity than activated carbon,which was 81.2μg·g-1and 53.8μg·g-1respectively.The adsorption data were fitted to the Langmuir adsorption model.The physical and chemical adsorption were identified on the adsorbent.     

Dye removal from colored textile wastewater using chitosan in binary systems

In this paper, the removal of two anionic dyes from textile effluent in single and binary systems was investigated. Direct Red 23 and Acid Green 25 were used as anionic dyes. The surface characteristics of chitosan were investigated using Fourier transform infrared. The effects of operational parameters such as chitosan dosage, initial dye concentration, salt and pH on dye removal were studied. The isotherms of dye adsorption were investigated. It was found that the isotherm data of Direct Red 23 and Acid Green 25 in single and binary systems followed Tempkin isotherm. In addition adsorption kinetics of dyes was studied in single and binary systems and rate sorption was found to conform to pseudo-second order kinetics with a good correlation. Results indicated that chitosan could be used as a biosorbent to remove the anionic dyes from contaminated watercourses in both single and binary systems of pollutants.     

壳聚糖印迹聚合物对Zn2+的吸附动力学

以Zn²⁺作为模板,加入分散剂石蜡、预交联剂甲醛、交联剂环氧氯丙烷,制得特性壳聚糖印迹聚合物,用X射线衍射仪表征了聚合物的结构,考察了聚合物用量、温度等对吸附Zn²⁺的影响,研究了印迹聚合物对Zn²⁺的吸附动力学、等温吸附特性。结果表明,印迹聚合物合成过程中打破了壳聚糖原有晶体的规整性,增加了大量的配位基团,使聚合物的吸附容量大大增加,同时聚合物对Zn²⁺有很好的选择吸附性,对Zn²⁺、Cd²⁺、Mg²⁺、Mn²⁺溶液的分离因子均大于1.5;印迹聚合物能快速吸附溶液中Zn²⁺,整个吸附过程符合拟二级动力学模型：t/Q_t=8.1744+2.0186t,相关系数为0.998,吸附平衡容量模型计算值与实验值较为吻合;印迹聚合物对Zn²⁺的等温吸附过程符合Langmuir吸附等温吸附模型：C_e/Q_e=1.3297+0.02701C_e,最大吸附容量为37.023 mmol/g,吸附过程主要以单分子层的吸附形式进行。     

Optimization and mechanisms analysis of indigo dye removal using continuous electrocoagulation

Electrocoagulation (EC) is among the most effective techniques that remove color and decontaminate effluent. Coagulants are delivered in situ by anode corrosion. In this research, indigo dye removal using iron electrodes in continuous electrocoagulation process and the responsible species for decolorization were investigated. The Response Surface Methodology (RSM) was used to optimize the process parameters. The finding in this study shows that at fixed conductivity at 15,000 μS·cm^-1, the neutral conditions (pH from 6 to 8), the low absorbance, the low flow rate and the high voltage level enhance the color removal efficiency. The high R² value of 97.8% and ANOVA analyses show a good correlation between the experimental and predicted results. Under the optimum conditions, which are pH of 7.5, solution concentration of 60 mg·L^-1, inlet flow rate of 2 L·min^-1 and voltage of 47 V, the predicted decolorization of 94.083% was achieved at 93.972% with a total cost of 0.0927 USD·m^-3 of treated effluent. At the optimum pH (7.5), the zeta potential value (-4 mV) of the effluent during EC match with the one of iron Ⅲ hydroxide. The dye removal is ensured thanks to physical adsorption and flocculation. The results exposed in this work prove that the continuous electrocoagulation process could be successfully used for indigo dye removal at industrial scale.     

Static and dynamic adsorption of fluoride using La(Ⅲ)-loaded chitosan beads crosslinked with EGDE

利用乙二醇二缩水甘油醚(EGDE)替代戊二醛对壳聚糖微球进行交联,然后负载稀土镧离子La(Ⅲ),制备得到新型的除氟剂（CEB-La）。研究了CEB-La对F^-的静态和动态吸附性能。静态吸附实验结果表明：该除氟剂的静态吸附条件为pH7.0、温度50℃、吸附时间60 min、振荡频率120 r·min^-1;当CEB-La用量3 g·L^-1时,对浓度10 mg·L^-1含氟水的除氟率可达92.9%;CEB-La对F^-的吸附过程符合Langmuir和Freundlich吸附等温线,饱和吸附容量为25.7 mg·g^-1;拟二级动力学方程能较好地描述CEB-La对F^-的吸附动力学过程;CEB-La吸附饱和后,经NaOH溶液处理后再与镧离子螯合,可有效再生;共存阴离子特别是CO ^{2 -}₃ 和HCO^-₃对CEB-La的除氟性能有不利影响。动态吸附实验结果表明：进水流量3 ml·min^-1时,CEB-La适于处理F^-浓度2～15 mg·L^-1的含氟水;利用Thomas模型可较好地描述CEB-La对F^-的动态吸附特征,动态饱和吸附容量为3.67 mg·g^-1。因此,CEB-La的除氟性能优越,再生方法简单,使用成本较低,具有较好的应用前景。     

Synthesis of cationic polymeric adsorbent and dye removal isotherm,kinetic and thermodynamic

Poly(quaternary ammonium salt) (PQAS) as a cationic polymeric adsorbent was synthesized and characterized by FTIR. Isotherm, kinetic and thermodynamic of dye removal from single and binary systems was investigated. Acid Blue 25 (AB25) and Acid Red 18 (AR18) were used. The effect of operational parameters (adsorbent dose, pH, dye concentration and salt) on dye removal was studied. The dye removal followed the Langmuir isotherm and pseudo-first order kinetics. The adsorbent maximum dye adsorption capacity (Q₀) was 2000 and 1667 mg/g for AB25 and AR18, respectively. The thermodynamic data showed that dye adsorption was spontaneous, endothermic, and a physisorption reaction.     

壳聚糖季铵盐对啤酒污水的絮凝研究

介绍了以3-氯-2-羟丙基三甲基氯化铵为改性剂接枝改性壳聚糖,制备了2-羟丙基三甲基壳聚糖季铵盐。用其对啤酒污水进行了絮凝处理,讨论了沉降时间,壳聚糖季铵盐的用量,pH值对啤酒污水絮凝效果的影响。结果表明:当沉降时间t=18 min,壳聚糖季铵盐添加量为10 mg/L,pH=8时,絮凝效果最好,污水的浊度值可降至3.5。     

L-胱氨酸交联球形壳聚糖凝胶的制备与Cu2+吸附性能

以L-胱氨酸(L-CYS)作为交联剂,利用滴液成球法制备交联球形壳聚糖凝胶,用傅里叶红外光谱、¹³C NMR、扫描电镜对产物进行了表征,结果表明L-CYS与壳聚糖发生了酰胺化及酯化反应,并且制得的凝胶内部存在着疏松的网络状大孔。交联剂L-CYS中的二硫键有助于二价铜离子的吸附。以L-CYS交联得到的球形壳聚糖凝胶对Cu²⁺的吸附量达到了72.96 mg·g^-1,接近于未交联的球形壳聚糖凝胶的吸附量,而耐溶胀性优于未交联的壳聚糖凝胶。     

Mechanically activated starch magnetic microspheres for Cd(Ⅱ) adsorption from aqueous solution

Magnetic starch microspheres(AAM-MSM) were synthesized via an inverse emulsion graft copolymerization by using mechanically activated cassava starch(MS) as a crude material, acrylic acid(AA) and acrylamide(AM) as graft copolymer monomers, and methyl methacrylate(MMA) as the dispersing agent and used as an adsorbent for the removal of Cd(II) ions from aqueous solution. Fourier-transform infrared spectroscopy(FT-IR), X-ray photoelectron spectroscopy(XPS), scanning electron microscopy(SEM), and vibrating sample magnetometry(VSM) were used to characterize the AAM-MSM adsorbent. The results indicated that AA, AM, and MMA were grafted to the MS, and the Fe_3 O_4 nanoparticles were encapsulated in the AAM-MSM adsorbent microspheres.The adsorbent exhibited a smooth surface, uniform size, and good sphericity because of the addition of the MMA and provided more adsorption sites for the Cd(II) ions. The maximum adsorption capacity of Cd(II) on the AAM-MSM was 39.98 mg·g~(-1). The adsorbents were superparamagnetic, and the saturation magnetization was 16.7 A·m~2·kg~(-1). Additionally, the adsorption isotherms and kinetics of the adsorption process were further investigated. The process of Cd(II) ions adsorbed onto the AAM-MSM could be described more favorably by the pseudo-second-order kinetic and Langmuir isothermal adsorption models, which suggested that the chemical reaction process dominated the adsorption process for the Cd(II) and chemisorption was the rate-controlling step during the Cd(II) removal process.