麦饭石负载壳聚糖对As(Ⅴ)的吸附性能研究

利用麦饭石负载壳聚糖制备一种复合吸附剂.研究了复合壳聚糖对As(Ⅴ)的吸附.结果表明:在PH值为4～7,吸附时间为40 min,复合壳聚糖对As(Ⅴ)的去除率达99%以上,残余As(Ⅴ)浓度低于国家综合排放标准(0.5 mg/L).通过对实验数据运用相关数学模型拟合,表明复合壳聚糖对As(Ⅴ)的吸附符合Iangmuir和Freundlich吸附等温式,最大吸附量q<,max>为39.1850 mg/g,n为4.7902,相关系数分别为:0.9967、0.9489.吸附过程动力学适合二级动力学方程.     

泡沫镍负载二氧化钛光电协同催化氧化砷

通过化学复合镀的方法制备成催化材料,TiO2粉末与镍磷合金共沉积在泡沫镍表面上,并通过光、电催化的方法将3价砷(As(III))氧化为5价砷(As(V))进行吸附试验。结果表明,As(III)吸附在7 h后达到平衡,As(V)吸附在5 h后达到平衡;As(III)和As(V)的吸附动力学与拟2级动力学特征相一致。在光催化、电催化和光电催化3种氧化As(III)的方法中,光电催化的效果最好;当As(III)的初始质量浓度为1 mg/L时,使用光电催化方法的除砷率能达到80.76%。     

蔗渣炭-镁铁双金属氧化物吸附剂对水中As(V)的吸附研究

采用共沉淀和焙烧法制备蔗渣炭-镁铁双金属氧化物(蔗渣炭-镁铁LDO),对合成的吸附材料进行表征,研究其对吸附As(V)的影响因素。结果表明,在p H=3.0~10时,蔗渣炭-镁铁LDO吸附剂对As(V)的吸附量较高。准2级动力学模型可用于描述其对As(V)的吸附动力学过程,吸附等温线符合Langmuir等温方程,其对As(V)的最大吸附量为25.40 mg/g。蔗渣炭-镁铁LDO受共存K~+、Na~+、Ca~(2+)、Mg~(2+)离子的影响较小,共存Cl~-、NO_3~-、SO_4~(2-)、CO_3~(2-)、HPO_4~(2-)离子影响较大,其影响大小顺序为HPO_4~(2-)CO_3~(2-)SO_4~(2-)Cl~-NO_3~-。材料再生循环利用4次后,对质量浓度20.0 mg/L的As(V)的吸附效率大于90%。     

磁性壳聚糖/膨润土的制备及其对铬(Ⅵ)的吸附研究

以膨润土为原料,先后用十二烷基苯磺酸钠及壳聚糖进行改性,最后用戊二醛交联,成功制备了磁性壳聚糖/膨润土复合吸附材料。采用静态吸附研究了吸附材料对水中铬(Ⅵ)的吸附性能,并研究了金属离子初始浓度、吸附时间、溶液pH、吸附剂投加量等对吸附效果的影响。实验结果表明:吸附材料在铬(Ⅵ)初始浓度为30 mg/L,吸附时间80 min,pH=3,投加量为2 g/L,吸附温度为323K时,脱除率可达95%以上;吸附动力学遵循准二级动力学模型。     

硅藻土复合磁性壳聚糖对铬(Ⅵ)离子吸附性能

以硅藻土、壳聚糖和Fe3O4为主要原料,制得硅藻土复合磁性壳聚糖材料DE/M-CS。分别考察了Fe3O4和壳聚糖与硅藻土质量比、pH、吸附时间、吸附温度等对铬(Ⅵ)离子吸附性能的影响。结果表明,低温有利于吸附,当m(Fe3O4)∶m(壳聚糖)∶m(硅藻土)=1∶1∶1、溶液pH为3、温度为15℃、吸附时间为6 h、达到吸附平衡时,DE/M-CS对铬(Ⅵ)离子吸附量为47.8 mg/g;吸附符合Langmuir等温模型,符合准二级动力学模型,吸附为放热反应。在吸附材料吸附饱和后,可以采用0.1 mol/L氢氧化钠溶液进行再生利用,重复使用4次后,DE/M-CS对铬(Ⅵ)离子吸附量为37.8 mg/g。     

SiO_2/CS交联复合吸附剂的制备

研究了对二氧化硅加入壳聚糖(CS)、硅烷,进行改性、冷冻干燥制备气凝胶复合吸附剂,探索对Fe⁽²⁺⁾的吸附特性。吸附等温线符合Langmiur吸附模型,其最大吸附量333.3 mg/g,吸附常数0.75 L/mg。吸附动力学符合二级动力学方程,吸附速率常数1.056 10 g/(mg·min),吸附容量125 mg/g。交联剂和冷冻干燥处理,提高了SiO_2/CS吸附剂的吸附性能。     

离子交换纤维除As(Ⅴ)性能研究

研究比较了几种吸附材料的除As(Ⅴ)性能,结果发现,颗粒活性炭的除As(Ⅴ)效果较差,活性氧化铝对As(V)有一定的去除效果,离子交换纤维(IEF)除As(Ⅴ)的效果最好.作者着重研究了IEF除As(Ⅴ)的吸附等温线和反应动力学,考察了pH、共存阴离子对IEF除As(Ⅴ)的影响.研究发现,Freundlich吸附等温线模型要好于Langmuir模型.吸附速率符合拟一级反应动力学.IEF的除As(Ⅴ)潜力较大,在As(Ⅴ)初始质量浓度为25 mg/L时,其吸附As(Ⅴ)的能力达285mg/g.pH偏酸性有利于吸附的进行.但共存离子的存在影响砷的吸附,通过负载铁到IEF上,可有效地解决这一问题,且总的吸附As(Ⅴ)的能力有一定的提高.     

Cu/N掺杂的木质素对水中阴离子的高选择吸附性及其对As(V)的高效吸附

木质素是一种广泛应用于去除水中重金属离子的吸附剂。原料可以从黑液中提取。利用木质素与三乙烯四胺(TETA)、CuCl2进行反应,得到了一种Cu/N掺杂的新型改性木质素吸附剂,其对特定阴离子具有高吸附率和高选择性。系统研究了Cu N掺杂的木质素(Cu/N-Lignin)、N掺杂的木质素(N-Lignin)和未掺杂的木质素(U-Lignin)在三种阴离子As(V)、Cl-和Cr(VI)上的吸附能力。在相同吸附条件下,Cu/N-Lignin对阴离子的选择性为Cl-Cr(VI)As(V)。从结果中可以看出,HAsO42-和N之间的氢键能够提高As(V)的选择性,掺杂Cu2+后,吸附剂对含氧阴离子的吸附能力进一步增强,说明了Cu2+与As之间具有一定的亲和力,最大吸附量高达253.4 mg/g。此外,As(V)初始浓度在10 mg/L的情况下,60 min内As(V)的去除率达到100%。吸附动力学曲线和吸附等温线分别遵循伪二阶和朗缪尔模型。     

SiO_2/CS交联复合吸附剂的制备

研究了对二氧化硅加入壳聚糖(CS)、硅烷,进行改性、冷冻干燥制备气凝胶复合吸附剂,探索对Fe~(2+)的吸附特性。吸附等温线符合Langmiur吸附模型,其最大吸附量333.3 mg/g,吸附常数0.75 L/mg。吸附动力学符合二级动力学方程,吸附速率常数1.056 10 g/(mg·min),吸附容量125 mg/g。交联剂和冷冻干燥处理,提高了SiO_2/CS吸附剂的吸附性能。     

印染硫化黑废水的铝盐壳聚糖絮凝试验

采用硫酸铝与壳聚糖复合絮凝剂处理某厂含硫化黑印染废水,通过正交试验对处理效果进行了优化,并进行了吸附动力学研究。结果表明,硫酸铝与壳聚糖可发生化学键合作用,当硫酸铝与壳聚糖复合质量比为10∶1,投加量为30 mg/L,p H为6~10时,对TOC为63.6 mg/L的印染硫化黑废水的TOC去除率达75.22%,脱色率达82.45%。吸附过程符合拟一级动力学方程,吸附活化能为9 k J/mol。     

Arsenic adsorption mechanism on clay minerals and its dependence on temperature

In the present study, the As(V) removal efficiency of different clay minerals was investigated as a function of solution pH, time, As(V) concentration, and temperature. Arsenic mobility was also investigated by determining the As(V) released from the loaded samples by leaching with various aqueous solutions. The kinetics of adsorption was observed to be fast and reached equilibrium within 3 h. As(V) adsorption on studied clays was pH dependent and maximum adsorption was achieved at pH 5.0. The maximum adsorption capacity was calculated by fitting the Langmuir equation to the adsorption isotherms and found to be 0.86, 0.64, and 0.52 mg As(V)/g of kaolinite, montmorillonite, and illite, respectively. The negative effect of temperature on As(V) adsorption showed the interactions to be exothermic. Based on the results, it was found that among the studied clay minerals, kaolinite was the best As(V) adsorbent and montmorillonite had strong retention capacity. The electrokinetic behavior of kaolinite and montmorillonite was modified in the presence of As(V), indicating that adsorption involves inner sphere surface complexation and strong specific ion adsorption.     

Simultaneous Removal of Fluoride and Arsenic from Aqueous Solution using Activated Red Mud

Red mud, a waste tailing from alumina production, was activated with calcination and acid treatment for simultaneous removal of F^? and As from water solution. After activation, the specific area and Si-O-M and Al-O-H functional groups of the activated red mud (ARM) greatly increased. Results showed that the adsorption equilibrium time for F^?, As(V), and As(III) was 18, 12, and 48 h, respectively. Kinetic data revealed that adsorption kinetics well followed the pseudo-second order model for F^?, As(V), and As(III). The presence of As(V)/As(III) improved the adsorption rate of F^?. With the co-existence of F^? and As, F^? adsorption was independent of initial solution pH between 4.0 and 10.0, and As adsorption between 2.0 and 10.0. Adsorption of F^?, As(V), and As(III) was better described by the Langmuir model than the Freundlich model, indicating that adsorption was in the form of a monolayer. Fluoride had a significant effect on As(V) adsorption, while the less affected As(III) adsorption. The presence of 1.0 mg/L As(III)/As(V) had no significant influence on F^? adsorption. ARM had high adsorption capacity for F^?, As(V), and As(III), which resulted from the increases in the specific area and Si-O-M and Al-O-H functional groups. Results demonstrated that ARM is a potential adsorbent for simultaneous removal of F^? and As from contaminated groundwater.     

Effective adsorption of As(V) and V(V) ions from water samples using 2,4-dinitrophenylhydrazine functionalized sodium dodecyl sulfate-coated magnetite nanoparticles

In this study, 2,4-DNPH coated magnetite was used for removal of As(V) and V(V) ions from aqueous solution. The synthesized nanoparticles were characterized by XRD analysis, FT-IR, SEM, and SEM-EDXS measurement. The size of the nanoparticles according to SEM was obtained as around 20–35 nm. Equilibrium isotherm data showed that the Langmuir–Freundlich model was in a good agreement with the experimental data according to high correlation coefficient. The maximum adsorption capacities of As(V) and V(V) on adsorbent were 338.4 and 266.8 mg g^?1, respectively. Kinetic study showed that the fractal like-PSO model was appropriate to describe the adsorption process. The optimum pH was obtained to be 7 and 5 for As(V) and V(V) ions, respectively.     

Response surface modeling,isotherm, thermodynamic and optimization study of arsenic (V) removal from aqueous solutions using modified bentonite-chitosan (MBC)

Arsenic contamination, a worldwide concern, has received a great deal of attention due to its toxicity and carcinogenicity. In the present study, we focused on the combined application of modified bentonite and chitosan (MBC) for the removal of As(V). Arsenic removal experiments were carried out to determine the amount of As(V) adsorbed as a function of pH (2-8), sorbent dosage (0.1-1.5 g/L), As(V) concentration (20-200mg/L) and time (60-240 min). The system was optimized by means of response surface methodology. The analysis of variance (ANOVA) of the quadratic model demonstrated that the model was highly significant (R²≈97.3%). Optimized values of pH, sorbent dosage, initial As(V) concentration and time were found to be 3.7, 1.40 g/L, 69mg/L, and 167min, respectively. The results reveal that the prepared adsorbent has a high adsorption capacity (122.23mg/g) for As(V) removal. Among the isotherm models used, the Langmuir isotherm model was the best fit for the obtained data. The adsorption kinetics following a pseudo-second-order kinetic model was involved in the adsorption process of As(V). Thermodynamic studies confirmed the spontaneous and endothermic character of adsorption process.     

Arsenic adsorption on goethite nanoparticles produced through hydrazine sulfate assisted synthesis method

Goethite nanoparticles synthesized using hydrazine sulfate as a modifying agent were evaluated for As(V) adsorption capacity. The nanoparticles were characterized for their morphological and structural features. The precipitated goethite particles were spherical with particle size of less than 10 nm. Batch adsorption study was carried out systematically varying parameters such as pH, contact time, initial As(V) concentration and adsorbent doses. The Langmuir isotherm represented the equilibrium data well and the estimated monolayer adsorption capacity at ambient temperature was 76 mg/g, which is significantly higher than most of the adsorbents reported in the literature. Adsorption kinetic data were better represented by the pseudo-second order kinetic model. Intra-particle diffusion played a significant role in the rate controlling process in the initial hour. Desorption study showed that the loaded adsorbent could be regenerated when treated with dilute sodium hydroxide solution of pH 13.     

Dispersion of FeOOH on Chitosan Matrix for Simultaneous Removal of As(III) and As(V) from Drinking Water

Bio-inorganic chitosan based spherical shaped beads were prepared by dispersing rod-shaped FeOOH nanoparticles into a chitosan matrix for the removal of pure As(III) and As(V) from aqueous media, such as drinking water. A homogeneous mixture of chitosan and ferric nitrate, ferric chloride was prepared respectively with or without oxalic acid. The mixture was added dropwise in to a NaOH bath, where iron salts reacted with NaOH to form FeOOH particles. The scanning electron microscopy (SEM) showed that rod shaped FeOOH particles were distributed homogenously in the chitosan matrix. Diffuse reflective UV-vis (DRUV) spectra revealed that hydrated iron oxide formed a complex with functional groups in chitosan. Adsorption of As(III) and As(V) on different iron salt based bead was found to be pH dependent. The bead prepared from iron nitrate showed better performance for arsenic removal from aqueous solution over the bead that was prepared using iron chloride salt. The bead prepared using chitosan and iron-FeOOH is known as a chitosan-iron oxyhydroxide (CFOH) bead. The CFOH beads were found to be more efficient in removing As(III) from the solution compared to As(V). The adsorption of As(III) and As(V) from aqueous solution on CFOH beads was studied under equilibrium conditions in the concentration range of 1 mg/L to 50 mg/L in the presence of 0.05 M NaNO₃ at pH 6.5 and 298 K temperature. The maximum adsorption capacity of the CFOH bead was found to be 5.4 mg/g for As(V) and 7.2 mg/g for As(III) using the Langmuir equation. The presence of sulphate, phosphate, and silicate in aqueous solution had no effects on adsorption of either As(III) or As(V) on CFOH beads but decreased significantly at pH> 8.     

Removal of As(V) Using an Iron-Impregnated Ion Exchange Bead

The ability of an iron-impregnated ion exchange bead (PWX5) to remove As(V) from ground water was investigated. The effects of particle size, solution pH, As(V) concentration, competition, adsorbent concentration, temperature, iron content, and iron accessibility on removal kinetics and/or equilibrium were determined. PWX5's performance was compared to other iron-based adsorbents, primarily Bayoxide® E-33 (E-33), a granular ferric oxide, for arsenic removal performance. All of the factors cited impacted either the amount of As(V) adsorbed or the rate of adsorption. Stirred batch reactor data showed the rate of adsorption increased as particle size decreased and bottle point isotherm data showed As(V) adsorption maximum capacity increased with higher initial adsorbate concentration. The presence of phosphate and silicate reduced the amount of As(V) adsorbed as did a pH > 7.0. PWX5 is durable, rather homogeneous in size and effective at removing As(V). It is a viable alternative to E-33 which has a wider size distribution and wears more easily.     

主要理化因素对FeCl_3除砷的影响

采用FeCl3作为化学沉淀除As药剂,研究了原水pH值、Fe/As质量比、搅拌参数、反应温度对As(V)去除效果的影响。试验结果表明,各因素的影响大小依次为:原水pH值>反应温度>Fe/As质量比>搅拌参数;FeCl3除As(V)的最佳反应条件为:原水pH值为9、反应温度为30℃、Fe/As质量比为1.0、搅拌转速为300/100/50 r/min及其对应搅拌时间为1/19/10 min、搅拌结束后静置90 min,As(V)的质量浓度由初始时的100 mg/L降低至3.8 mg/L,除As(V)率达到95%以上。连续提取方法分析沉淀样品中As(V)的形态结果表明,各种形态含量大小顺序依次为:与结晶态铁氧化物结合态>专性吸附态>与无定型铁氧化物结合态>水溶态>非专性吸附态;FeCl3与As(V)主要通过络合作用(如生成内层络合物FeAsO4沉淀)、吸附作用(专性吸附)达到除As目的,且生成的沉淀稳定性较强,不易产生二次污染。通过红外光谱测定发现,在波数为830 cm-1左右存在一个较为显著的波峰,这可能与沉淀样品中形成的内层络合物含有Fe—As—O以及吸附在铁氧化物上的As(V)含有As—O有关。     

Removal of As(V) and Cr(VI) in aqueous solution by sand media simultaneously coated with Fe and Mn oxides

In this research, sand media simultaneously coated with iron and manganese (iron and manganese coated sand, IMCS) were applied to treat synthetic wastewater contaminated with both Cr(VI) and As(V). Scanning electron microscopy (SEM) and X-ray diffraction spectroscopy (XRD) were used to characterize the surface properties of the coated layer of IMCS. Adsorption of Cr(VI) and As(V) onto IMCS followed a typical anionic type, showing a gradual decrease of adsorption as the solution pH increased. In a single system, IMCS showed a greater adsorption capacity for As(V) than that for Cr(VI) over the entire solution pH range. In a binary system, As(V) preferentially occupied the limited adsorption sites on IMCS and therefore Cr(VI) adsorption was suppressed. This result indicates that As(V) adsorption onto the surface of IMCS occurs through a strong chemical bonding such as an inner-sphere complex. As(V) adsorption onto the IMCS was well described by second-order kinetics. From the adsorption isotherm experiments at pH 4, the maximum adsorbed amount of Cr(VI) and As(V) onto IMCS in a single system was 102 mg/kg and 455 mg/kg, respectively.     

纳米零价铁对水溶液中钒离子的吸附性能

采用液相还原法制备纳米零价铁(nZVI),采用PXRD, SEM, TEM, BET(N2吸脱附)和XPS等表征材料性能,考察了纳米零价铁用量、初始钒(V)浓度和初始pH对纳米零价铁吸附钒(V)性能的影响,测定了纳米零价铁对钒(V)的吸附等温线和吸附动力学曲线. 结果表明,制备的纳米零价铁具有典型的核?壳结构,粒径为10~30 nm,BET比表面积为53 m2/g. 纳米零价铁对钒(V)的吸附容量随纳米零价铁用量和初始pH增大而减小. 25℃时的平衡吸附容量为227.8 mg/g. Langmuir等温线方程可很好拟合纳米零价铁对钒(V)的吸附,纳米零价铁对钒(V)的吸附动力学曲线符合准二级动力学模型.