Removal of heavy metals through adsorption using sand

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Removal of heavy metals from aqueous solution by sawdust adsorption

The adsorption of lead, cadmium and nicel from aqueous solution by sawdust of walnut was investigated. The effect of contact time, initial metal ion concentration and temperature on metal ions removal has been studied. The equilibrium time was found to be of the order of 60 min. Kinetics fit pseudo first-order, second-order and intraparticle diffusion models, hence adsorption rate constants were calculated. The adsorption data of metal ions at temperatures of 25, 45 and 60~C have been described by the Freundlich and Langmuir isotherm models. The thermodynamic parameters such as energy, entropy and enthalpy changes for the adsorption of heavy metal ions have also been computed and discussed. Ion exchange is probably one of the major adsorption mechanisms for binding divalent metal ions to the walnut sawdust. The selectivity order of the adsorbent is Pb（I1）~Cd（II）〉Ni（I1）. From these results, it can be concluded that the sawdust of walnut could be a good adsorbent for the metal ions from aqueous solutions.     

Pb(Ⅱ) biosorption using chitosan and chitosan derivatives beads: Equilibrium, ion exchange and mechamsm studies

The study examined the adsorption of Pb(Ⅱ) ions from aqueous solution onto chitosan, chitosan-GLA and chitosan-alginate beads.Several important parameters influencing the adsorption of Pb(Ⅱ) ions such as initial pH, adsorbent dosage and different initial concentration of Pb(Ⅱ) ions were evaluated. The mechanism involved during the adsorption process was explored based on ion exchange study and using spectroscopic techniques. The adsorption capacities obtained based on non-linear Langmuir isotherm for chitosan, chitosan-GLA and chitosan-alginate beads in single metal system were 34.98, 14.24 and 60.27 mg/g, respectively. However,the adsorption capacity of Pb(Ⅱ) ions were reduced in the binary metal system due to the competitive adsorption between Pb(Ⅱ) and Cu(Ⅱ) ions. Based on the ion exchange study, the release of Ca~(2+), Mg~(2+), K~+ and Na~+ ions played an important role in the adsorption of Pb(Ⅱ) ions by all three adsorbents but only at lower concentrations of Pb(Ⅱ) ions. Infrared spectra showed that the binding between Pb(Ⅱ) ions and the adsorbents involved mostly the nitrogen and oxygen atoms. All three adsorbents showed satisfactory adsorption capacities and can be considered as an efficient adsorbent for the removal of Pb(Ⅱ) ions from aqueous solutions.     

改性栗壳吸附重金属离子的动力学及热力学研究

对改性板栗壳吸附Cr(VI)、Cu(II)及Ni(II)3种重金属离子过程的动力学和热力学进行研究。结果表明:改性板栗壳吸附Cr(VI)、Cu(II)和Ni(II)3种混合离子时存在拮抗的竞争关系,竞争吸附顺序为Cu(II)﹤Ni(II)﹤Cr(VI);与单独吸附过程相比,混合吸附平衡时,改性板栗壳对3种离子相应的去除率均有所降低,Cr(VI)去除率比单独吸附时降低20.2%,Cu(II)和Ni(II)分别降低40.7%和35.6%;拟二级动力学方程能很好地描述Cr(VI)、Cu(II)和Ni(II)在改性板栗壳上的单独和混合吸附过程,结果表明此3种重金属离子在改性板栗壳表面以化学吸附为主;热力学研究数据表明:改性板栗壳对Cr(VI)的吸附为吸热反应,对Cu(II)和Ni(II)的吸附为放热反应。     

Preparation of organically functionalized silica gel as adsorbent for copper ion adsorption

A novel adsorbent (AMPS-silica) was synthesized by bounding AMPS (2-acrylamido-2-methylpropanesulfonic acid) onto silica surface, which functioned with -methacryloxypropyltrimethoxysilane reagent. The adsorbent was characterized by nitrogen adsorption/ desorption measurement, thermogravimetric analysis (TGA) and potentiometric titration analysis. The TGA result indicated that the surface modification reactions introduced some organic functional groups onto the surface of silica. The surface area of AMPSsilica was 389.7 m2/g. The adsorbent was examined for copper ion removal in series of batch adsorption experiments. Results showed that the adsorption of Cu2+ onto AMPS-silica was pH dependent, and the adsorption capacity increased with increasing pH from 2 to 6. The adsorption kinetics showed that Cu2+ adsorption was fast and the data fitted well with a pseudo second- order kinetic model. The adsorption of Cu2+ onto AMPS-silica obeyed both Freundlich and Langmuir isotherms, with r2 = 0.993 and r2 = 0.984, respectively. The maximum Cu2+ adsorption capacity was 19.9 mg/g. The involved mechanism might be the adsorption through metal binding with organic functional groups such as carboxyl, amino and sulfonic groups. Cu2+ loaded on AMPS-silica could be desorbed in HNO3 solution, and the adsorption properties remain stable after three adsorption-desorption cycles.     

改性柚皮粉对水中Cu(Ⅱ)和Zn(Ⅱ)的吸附

基于柚皮中富含纤维素、木质素、多糖等可与重金属发生络合、螯合作用的物质,将农林及生活废弃物柚子皮作为重金属离子的吸附剂。采用经NaOH改性的柚皮粉吸附水中Cu(Ⅱ)和Zn(Ⅱ)。考察了pH、吸附时间、改性柚皮粉用量以及Cu(Ⅱ)和Zn(Ⅱ)初始浓度等因素对吸附的影响,测定了吸附等温线,对等温吸附规律及动力学进行了探讨。结果表明,pH、吸附时间、改性柚皮粉用量、Cu(Ⅱ)和Zn(Ⅱ)初始浓度等因素对吸附效果均有影响。吸附Cu(Ⅱ)的适宜条件为:pH5.4～5.5,吸附时间10min,改性柚皮粉用量0.2g/100mL,Cu(Ⅱ)初始浓度20～80mg/L。在该条件下,Cu(Ⅱ)去除率达95%以上。吸附Zn(Ⅱ)的适宜条件为:pH5.5～5.6,吸附时间60min,改性柚皮粉用量0.4g/100mL,Zn(Ⅱ)初始浓度小于80mg/L。在该条件下,Zn(Ⅱ)去除率达90%以上。等温吸附规律可用Freundlich和Langmuir模式较好地描述,吸附呈单分层形式,吸附性能良好。吸附动力学规律符合准一级、准二级和Elovich动力学模型。     

Adsorptive removal of heavy metal ions from industrial effluents using activated carbon derived from waste coconut buttons

Removal of heavy metal ions from industrial effluents by the activated carbon prepared by steam activation of waste coconut buttons through batch adsorption process.     

给水厂污泥对Hg(Ⅱ)的吸附性能

给水厂污泥具有较强的吸附能力,可作为从水溶液中去除重金属的潜在吸附剂。通过试验分析了给水厂污泥(WTR)作为吸附剂去除溶液中Hg(Ⅱ)时,pH值、Hg(Ⅱ)初始浓度、污泥粒径以及温度对Hg(Ⅱ)吸附性能的影响,确定了吸附过程的动力学及吸附等温模型,并探究了其吸附机理。结果表明：溶液pH值对给水厂污泥吸附Hg(Ⅱ)具有较大影响,当pH=8.0时吸附效果最佳。采用粒径较小的污泥有利于对Hg(Ⅱ)的吸附,污泥对Hg(Ⅱ)的吸附量随着初始浓度的增加而增加。给水厂污泥对Hg(Ⅱ)的吸附符合准二级动力学模型,平衡等温线符合Langmuir吸附等温模型,25℃条件下pH为7.0时污泥的饱和吸附量达到69.13 mg/g。升温有利于给水厂污泥对Hg(Ⅱ)的吸附。通过分析吸附前后污泥比表面积和微孔体积的变化发现,颗粒内扩散是给水厂污泥吸附Hg(Ⅱ)的限速步骤。     

Selective adsorption of silver ions from aqueous solution using polystyrene-supported trimercaptotriazine resin

Trimercaptotriazine-functionalized polystyrene chelating resin was prepared and employed for the adsorption of Ag(I) from aqueous solution. The adsorbent was characterized according to the following techniques: Fourier transform infrared spectroscopy, elemental analysis, scanning electron microscopy and the Brunauer-Emmet-Teller method. The effects of initial Ag(I) concentration, contact time, solution pH and coexisting ions on the adsorption capacity of Ag(I) were systematically investigated. The maximum adsorption capacity of Ag(I) was up to 187.1 mg/g resin at pH 0.0 and room temperature. The kinetic experiments indicated that the adsorption rate of Ag(I) onto the chelating resin was quite fast in the first 60 min and reached adsorption equilibrium after 360 min. The adsorption process can be well described by the pseudo second-order kinetic model and the equilibrium adsorption isotherm was closely fitted by the Langmuir model. Moreover, the chelating resin could selectively adsorb more Ag(I) ions than other heavy metal ions including: Cu(II), Zn(II), Ni(II), Pb(II) and Cr(III) during competitive adsorption in the binary metal species systems, which indicated that it was a highly selective adsorbent of Ag(I) from aqueous solution.     

Immobilization study of biosorption of heavy metal ions onto activated sludge

Activated sludge was immobilized into Ca-alginate beads via entrapment, and biosorption of three heavy metal ions, copper(Ⅱ), zinc(Ⅱ), and chromimum(Ⅱ), from aqueous solution in the concentration range of 10-100 mg/L was studied by using both entrapped activated sludge and inactivated free biomass at pH≤5. A biphasic metal adsorption pattern was observed in all immobilized biomass experiments. The biosorption of metal ions by the biosorbents increased with the initial concentration increased in the medium. The adsorption rate of immobilized pre-treated activated sludge(PAS) was much lower than that of free PAS due to the increase in mass transfer resistance resulting from the polymeric matrix. Biosorption equilibrium of beads was established in about 20 h and the adsorbed heavy metal ions did not change further with time. No significant effect of temperature was observed in the test for free biomass while immobilized PAS appeared to be strong temperature dependent in the test range of 10 and 40℃.Besides, the content of activated sludge in the calcium alginate bead has an influence on the uptake of heavy metals. The sorption equilibrium was well modeled by Langmuir isotherm, implying monomolecular adsorption mechanism. Carboxyl group in cell wall played an important role in surface adsorption of heavy metal ions on PAS.     

Chemically modified silica gel with 1-{4-[(2-hydroxy-benzylidene)amino]phenyl}ethanone: Synthesis, characterization and application as an efficient and reusable solid phase extractant for selective removal of Zn(II) from mycorrhizal treated fly-ash samples

1-{4-[(2-hydroxy-benzylidene)amino]phenyl}ethanone functionalized silica gel was synthesized and used as a highly efficient, selective and reusable solid phase extractant for separation and preconcentration of trace amount of Zn(II) from environmental matrices. The adsorbent was characterized by fourier transform infrared spectroscopy (FT-IR), elemental analysis,¹³C CPMAS NMR spectroscopy, scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and BET surface area analysis. The dependence of zinc extraction on various analytical parameters such as pH, type and amount of eluent, sample flow rate and interfering ions were investigated in detail. The material exhibited superior adsorption efficiency for Zn(II) with high metal loading capacity of 1.0 mmol/g under optimum conditions. After adsorption, the recovery (> 98%) of metal ions was accomplished using 1.0 mol/L HNO₃ as an eluent. The sorbent was also regenerated by microwave treatment in milder acidic environment (0.1 mol/L HNO₃). The lower detection limit and preconcentration factor of the present method were found out to be 0.04 μg/L and 312.5 respectively. The modified silica surface possessed excellent selectivity for the target analytes and the adsorption/desorption process remained effective for at least ten consecutive cycles. The optimized procedure was successfully implemented for the extraction of Zn(II) from mycorrhizal treated fly ash and pharmaceutical samples with reproducible results.     

Biosorption of cadmium(Ⅱ) and lead(Ⅱ) ions from aqueous solutions onto dried activated sludge

The removal of heavy-metal ions from aqueous solutions by using dried activated sludge has been investigated in batch systems. Effect of solution pH, initial metal ion concentration, and temperature were determined. The results of the kinetic studies showed that the uptake processes of the two metal ions(Cd(Ⅱ) and Pb(Ⅱ)) followed the pseudo-second-order rate expression. The equilibrium data fitted very well to both the Langmuir and Freundlich adsorption models. The FT-IR analysis showed that the main mechanism of Cd(Ⅱ) and Pb(Ⅱ) biosorption onto dried activated sludge was their binding with amide I group.     

Removal of copper ions from aqueous solution by calcium alginate immobilized kaolin

Kaolin has been widely used as an adsorbent to remove heavy metal ions from aqueous solutions. However, the lower heavy metal adsorption capacity of kaolin limits its practical application. A novel environmental friendly material, calcium alginate immobilized kaolin (kaolin/CA), was prepared using a sol-gel method. The e ects of contact time, pH, adsorbent dose, and temperature on Cu2+ adsorption by kaolin/CA were investigated. The Langmuir isotherm was used to describe the experimental adsorption, the maximum Cu2+ adsorption capacity of the kaolin/CA reached up to 53.63 mg/g. The thermodynamic studies showed that the adsorption reaction was a spontaneous and endothermic process.     

Ethyl thiosemicarbazide intercalated organophilic calcined hydrotalcite as a potential sorbent for the removal of uranium(VI) and thorium(IV) ions from aqueous solutions

This work was conducted to determine the practicability of using a new adsorbent 4-ethyl thiosemicarbazide intercalated,organophilic calcined hydrotalcite(ETSC-OHTC) for the removal of uranium(U(VI)),and thorium(Th(IV)) from water and wastewater.The FTIR analysis helped in realizing the involvement of nitrogen and sulphur atoms of ETSC in binding the metal ions through complex formation.Parameters like adsorbent dosage,solution pH,initial metal ions concentration,contact time and ionic strength,that influence adsorption phenomenon,were studied.The optimum pH for maximum adsorption of U(VI) and Th(IV) was found to be in the range 4.0-6.0.The contact time required for reaching equilibrium was 4 hr.The pseudo second-order kinetic model was the best fit to represent the kinetic data.Analysis of the equilibrium adsorption data using Langmuir,Freundlich and Sips models showed that the Freundlich model was well suited to describe the metal ions adsorption.The K F values were 25.43 and 29.11mg/g for U(VI) and Th(IV),respectively,at 30°C.The adsorbent can be regenerated effectively from U(VI) and Th(IV) loaded ones using 0.01mol/L HCl.The new adsorbent was quite stable for many cycles,without much reduction in its adsorption capacity towards the metals.     

CTAB改性地聚合物同时去除Cu(II)和Cr(VI)

地聚合物（Geopolymer,简称GP）是由含硅铝酸盐的偏高岭土（Metakaolin,简称MK）或固体废料（如粉煤灰）经碱性激活制备的立体网状结构无机聚合物,对大部分重金属阳离子有良好的吸附作用,但对以阴离子形态存在的重金属吸附效果很差.本研究以偏高岭土为主要原料制备GP,同时用CTAB进行改性,研究其化学组成变化及对典型以阴、阳离子形态存在的重金属Cr（VI）和Cu（II）的同时吸附作用.结果表明,pH为5、吸附时间为24 h、初始浓度为50 mg·L^-1、吸附剂投加量为1 g·L^-1时,CTAB-GP对Cu（II）的去除率达到98.6%,Cr（VI）的最高去除率为25.6%,同时还发现溶液中Cu（II）的存在对吸附Cr（VI）有较大促进作用.整体来看,两种金属混合吸附时很好地符合二级动力学规律,单溶质吸附很好地符合Langmuir和Freundlich等温式,Cu（II）和Cr（VI）的理论最大吸附量分别为147.1 mg·g^-1和63.1 mg·g^-1.XRD、FTIR和BET表征分析结果表明,CTAB-GP中即使存在季铵盐阳离子,但依然属于地聚合物.CTAB-GP可以不牺牲对重金属阳离子吸附性能的同时吸附阴离子,优于常规地聚合物,鉴于CTAB-GP的这种特性,其在重金属污染防治中显示出极大的应用前景.     

富里酸在聚苯乙烯微塑料上的吸附行为

主要探究富里酸(FA)在聚苯乙烯(PS)和HBCD-PS复合物(HBCD-PS)微塑料上的吸附特性与作用机制.结果表明,PS对FA几乎没有吸附效果,然而HBCD的存在显著地促进了FA在HBCD-PS上的吸附行为.W-M颗粒内扩散和Boyd扩散模型证实了HBCD-PS对FA的吸附过程主要受颗粒内扩散控制.HBCD-PS对...     

Removal of heavy metal ions from aqueous solution using red loess as an adsorbent

The adsorption behaviors of heavy metals onto novel low-cost adsorbent, red loess, were investigated. Red loess was characterized by X-ray diffraction, scanning electron microscopy and Fourier transform infrared spectra. The results indicated that red loess mainly consisted of silicate, ferric and aluminum oxides. Solution pH, adsorbent dosage, initial metal concentration, contact time and temperature significantly influenced the efficiency of heavy metals removal. The adsorption reached equilibrium at 4 hr, and the experimental equilibrium data were fitted to Langmuir monolayer adsorption model. The adsorption of Cu(II) and Zn(II) onto red loess was endothermic, while the adsorption of Pb(II) was exothermic. The maximum adsorption capacities of red loess for Pb(II), Cu(II) and Zn(II) were estimated to be 113.6, 34.2 and 17.5 mg/g, respectively at 25°C and pH 6. The maximum removal efficiencies were 100% for Pb(II) at pH 7, 100% for Cu(II) at pH 8, and 80% for Zn(II) at pH 8. The used adsorbents were readily regenerated using dilute HC1 solution, indicating that red loess has a high reusability. All the above results demonstrated that red loess could be used as a possible alternative low-cost adsorbent for the removal of heavy metals from aqueous solution.     

溶磷微生物改性生物炭吸附重金属的机理研究

利用磷溶菌（PSB）对稻壳（RB）和污泥（SB）生物炭进行不同时间的改性,研究了其对水体中Pb²⁺和Cd²⁺（1000mg/L）的修复机制.主要通过测定改性生物炭的理化特性和重金属含量,并利用结构方程模型研究了微生物改性生物炭对重金属的吸附机理.结果表明,PSB显著改善生物炭的孔径结构、比表面积BET （增加了12.5%~175.0%）和表面官能团.特别是还增加了生物炭中C和P元素的释放,促进了生物炭表面的生物矿化机制.PSB改性显著提高了生物炭对Pb²⁺和Cd²⁺的吸附作用（RB提高：Pb²⁺=9.5%~34.5%,Cd²⁺=34.7%~219.9%,SB提高：Pb²⁺=65.3%~101.3%,Cd²⁺=106.6%~248.6%）.通过Pb和Cd的修复差异,发现不同重金属对微生物的胁迫是导致改性生物炭对重金属的修复反应路径相反的原因.此外,结构方程模型证实6~12h的PSB改性效果最好,且BET不是主要影响因素.不同的生物质炭改性后的修复机制也存在明显差异,孔径结构（R_max²=0.99）是改性RB的主要吸附途径,化学沉淀（R_max²=0.99）是改性SB的主要吸附途径.     

两种碳酸系Fe-LDHs负载改性沸石对Cd(Ⅱ)吸附特性对比研究

为提升以沸石为代表的天然吸附材料对重金属污染物吸附效果,并将新型功能材料层状双金属氢氧化物（layered double hydroxides,LDHs）有效应用于实际工程,采用水浴-共沉淀法制备两种Fe系碳酸型LDHs即时负载于沸石填料表面,利用场发射扫描电子显微镜（SEM）、能谱分析仪（EDS）和X射线衍射仪（XRD）对改性前后的沸石表面形态、化学成分和晶体结构进行表征;通过等温吸附及解吸附、吸附动力学、吸附热力学、竞争离子吸附和不同pH吸附试验,对比原始及改性沸石对Cd（Ⅱ）的吸附效果及其作用机理.结果表明:①改性沸石对Cd（Ⅱ）的吸附过程更符合Langmuir等温吸附模型和准二级动力学模型.②相较于原始沸石,两种改性沸石对Cd（Ⅱ）的吸附性能明显提升,且MgFe-LDHs负载改性沸石理论最大饱和吸附容量更高.③沸石改性后对Cd（Ⅱ）的吸附由放热过程变为吸热过程.④吸附时间、竞争离子及pH对沸石吸附Cd（Ⅱ）的效果产生不同程度的影响.研究显示,MgFe-LDHs负载改性沸石最大饱和吸附容量显著提升,吸附能力更强,且在不同条件下均表现出优良的吸附特性,具有作为高效除镉填料的潜力.      

Evaluation of the adsorptive capacity of peanut hull pellets for heavy metals in solution

This study assessed the potential of peanut hull pellets to capture metal ions from wastewater and compared their performance to that of raw peanut hulls and a commercial grade ion-exchange resin. The uptake of Cu²⁺, Cd²⁺, Zn²⁺, and Pb²⁺ onto these media was investigated using a system of standardized batch adsorbers under steady state and transient rate conditions. The influence of the pelletizing process on the rate of metal ion sorption was evaluated by comparing the rate and extent of metal ion uptake onto peanut hull pellets vs. raw peanut hulls. Although a slight reduction in rate of adsorption was apparent for metal ion adsorption onto the pellets, equilibrium capacity was unaffected. Peanut hull pellets are an effective adsorbent for metal ion removal. Though their capacity is lower than that of commercial grade ion-exchange resins, their low cost makes them an attractive option for the treatment of low-strength metal ion waste streams in once-through fixed bed applications.