Simultaneous removal and oxidation of arsenic from water by δ-MnO2 modified activated carbon

The ubiquitous arsenic in groundwater poses a great risk to human health due to its environmental toxicity and carcinogenicity. In the present work, a new adsorbent, δ-MnO₂ modified activated carbon, was prepared, and its performance for the uptake of arsenate and arsenite species from aqueous solutions was investigated by batch experiments. Various techniques, including FESEM-EDX, p-XRD, XPS and BET surface area analysis, were employed to characterize the properties of the adsorbent and the arsenic adsorption mechanisms. The results showed that δ-MnO₂ covered on the surface and padded in the pores of the activated carbon. Adsorption kinetic studies revealed that approximately 90.1% and 76.8% of As(III) and As(V), respectively, were removed by the adsorbent in the first 9 hr, and adsorption achieved equilibrium within 48 hr. The maximum adsorption capacities of As(V) and As(III) at pH 4.0 calculated from Langmuir adsorption isotherms were 13.30 and 12.56 mg/g, respectively. The effect of pH on As(V) and As(III) removal was similar, and the removal efficiency significantly reduced with the increase of solution pH. Arsenite oxidation and adsorption kinetics showed that the As(V) concentration in solution due to As(III) oxidation and reductive dissolution of MnO₂ increased rapidly during the first 12 min, and then gradually decreased. Based on the XPS analysis, nearly 93.3% of As(III) had been oxidized to As(V) on the adsorbent surface and around 38.9% of Mn(IV) had been reduced to Mn(II) after As(III) adsorption. This approach provides a possible method for the purification of arsenic-contaminated groundwater.     

Effect of competing solutes on arsenic（Ⅴ） adsorption using iron and aluminum oxides

The study focused on the effect of several typical competing solutes on removal of arsenic with Fe_2O_3 and AL_2O_3.The test results indicate that chloride,nitrate and sulfate did not have detectable effects,and that selenium(Ⅳ)(Se(Ⅳ))and vanadium(Ⅴ)(V(Ⅴ)) showed slight effects on the adsorption of As(Ⅴ)with Fe_2O_3.The results also showed that adsorption of As(Ⅴ)on AL_2O_3 was not affected by chloride and nitrate anions,but slightly by Se(Ⅳ)and V(Ⅴ)ions.Unlike the adsorption of As(Ⅴ)with Fe_2O_3,that with Fe_2O_3 was affected by the presence of sulfate in water solutions.Both phosphate and silica have significant adverse effects on the adsorption of As(Ⅴ)adsorption with Fe_2O_3 and Al_2O_3.Compared to the other tested anions,phosphate anion was found to be the most prominent solute affecting the As(Ⅴ)adsorption with Fe_2O_3 and Al_2O_3.In general,Fe_2O_3 has a better performance than Al_2O_3 in removal of As(Ⅴ)within a water environment where multi competing solutes are present.     

Removal of phosphate by Fe-coordinated amino-functionalized 3D mesoporous silicates hybrid materials

Phosphate removal from aqueous waste streams is an important approach to control the eutrophication downstream bodies of water. A Fe(III) coordinated amino-functionalized silicate adsorbent for phosphate adsorption was synthesized by a post-grafting and metal cation incorporation process. The surface structure of the adsorbent was characterized by X-ray di raction, N2 adsoropion/desoprotion technique, and Fourier transform infrared spectroscopy. The experimental results showed that the adsorption equilibrium data were well fitted to the Langmuir equation. The maximum adsorption capacity of the modified silicate material was 51.8 mg/g. The kinetic data from the adsorption of phosphate were fitted to pseudo second-order model. The phosphate adsorption was highly pH dependent and the relatively high removal of phosphate fell within the pH range 3.0–6.0. The coexistence of other anions in solutions has an adverse e ect on phosphate adsorption; a decrease in adsorption capacity followed the order of exogenous anions: F?? > SO2?? 4 > NO??3 > Cl??. In addition, the adsorbed phosphate could be desorbed by NaOH solutions. This silicate adsorbent with a large adsorption capacity and relatively high selectivity could be utilized for the removal of phosphate from aqueous waste streams or in aquatic environment.     

Preparation and evaluation of Zr-β-FeOOH for efficient arsenic removal

A Zr-β-FeOOH adsorbent for both As(V) and As(III) removal was prepared by a chemical co-precipitation method.Compared with β-FeOOH,the addition of Zr enhanced the adsorption capacities for As(V) and As(III),especially As(III).The maximum adsorption capacities for As(III) and As(V) were 120 and 60mg/g respectively at pH 7.0,much higher than for many reported adsorbents.The adsorption data accorded with Freundlich isotherms.At neutral pH,for As(V),adsorption equilibrium was approached after 3 hr,while for As(III),adsorption equilibrium was approached after 5 hr.Kinetic data fitted well to the pseudo second-order reaction model.As(V) elimination was favored at acidic pH,whereas the adsorption of As(III) by Zr-β-FeOOH was found to be effective over a wide pH range of 4-10.Competitive anions hindered the adsorption according to the sequence:phosphate > silicate > bicarbonate > sulfate > nitrate,while Ca2+ and Mg2+ increased the removal of As(III) and As(V) slightly.The high adsorption capability and good performance in other aspects make Zr-β-FeOOH a potentially attractive adsorbent for the removal of both As(III) and As(V) from water.     

Fast and efficient aqueous arsenic removal by functionalized MIL-100(Fe)/rGO/δ-MnO2 ternary composites: Adsorption performance and mechanism

Because of its significant toxicological effects on the environment and human health,arsenic(As) is a major global issue.In this study,an Fe-based metal-organic framework(MOF)(Materials of Institut Lavoisier:MIL-100(Fe)) which was impregnated with reduced graphene oxide(rGO) by using a simple hydrothermal method and coated with birnessitetype manganese oxide(δ-MnO_2) using the one-pot reaction process(MIL-100(Fe)/rGO/δ-MnO_2 nanocomposites) was synthesized and applied successfully in As removal.The removal efficiency was rapid,the equilibrium was achieved in 40 min and 120 min for As(Ⅲ) and As(Ⅴ),respectively,at a level of 5 mg/L.The maximum adsorption capacities of As(Ⅲ) and As(Ⅴ) at pH 2 were 192.67 mg/g and 162.07 mg/g,respectively.The adsorbent revealed high stability in pH range 2-9 and saturated adsorbent can be fully regenerated at least five runs.The adsorption process can be described by the pseudo-second-order kinetic model and Langmuir monolayer adsorption.The adsorption mechanisms consisted of electrostatic interaction,oxidation and inner sphere surface complexation.     

A laboratory scale study on arsenic（Ⅴ） removal from aqueous medium using calcined bauxite ore

The present work deals with the As（Ⅴ） removal from an aqueous medium by calcined refractory grade bauxite （CRB） as a function of solution pH, time, As（Ⅴ） concentration and temperature. The residual As（Ⅴ） was lowered from 2 mg/L to below 0.01 mg/L in the optimum pH range 4.0-7.0 using a 5 g/L CRB within 3 h contact time. The adsorption data fits well with Langmuir isotherm and yielded Langmuir monolayer capacity of 1.78 mg As（Ⅴ）/g of CRB at pH 7.0. Presence of anions such as silicate and phosphate decreased As（Ⅴ） adsorption efficiency. An increase temperature resulted a decrease in the amount of As（Ⅴ） adsorbed by 6%. The continuous fixed bed column study showed that at the adsorbent bed depth of 30 cm and residence time of 168 min, the CRB was capable of treating 340 bed volumes of As（V） spiked water （C0 = 2 mg/L） before breakthrough （Ce = 0.01 mg/L）. This solid adsorbent, although not reusable, can be considered for design of adsorption columns as an efficiency arsenic adsorption media.     

Preparation and characterization of a lipoid adsorption material and its atrazine removal performance

A novel adsorbent named lipoid adsorption material (LAM), with a hydrophobic nucleolus (triolein) and a hydrophilic membrane structure (polyamide), was synthesized to remove hydrophobic organic chemicals (HOCs) from solution. Triolein, a type of lipoid, was entrapped by the polyamide membrane through an interfacial polymerization reaction. The method of preparation and the structure of the LAM were investigated and subsequent experiments were conducted to determine the characteristics of atrazine (a type of HOC) removal from wastewater using LAM as the adsorbent. The results showed that LAM had a regular structure compared with the prepolymer, where compact particles were linked with each other and openings were present in the structure of the LAM in which the fat drops formed from triolein were entrapped. In contrast to the atrazine adsorption behavior of powdered activated carbon (PAC), LAM showed a persistent adsorption capacity for atrazine when initial concentrations of 0.57, 1.12, 8.31 and 19.01 mg/L were present, and the equilibrium time was 12 hr. Using an 8 mg/L initial concentration of atrazine as an indicator of HOCs in aqueous solution, experiments on the adsorption capacity of the LAM showed 69.3% removal within 6–12 hr contact time, which was close to the 75.5% removal of atrazine by PAC. Results indicated that LAM has two atrazine removal mechanisms, namely the bioaccumulation of atrazine by the nucleous material and physical adsorption to the LAM membrane. Bioaccumulation was the main removal mechanism.     

Arsenic removal from groundwater by acclimated sludge under autohydrogenotrophic conditions

Arsenic in the environment is attracting increasing attention due to its chronic health effects. Although arsenite(As(III)) is generally more mobile and more toxic than arsenate(As(V)), reducing As(V) to As(III) may still be a means for decontamination, because As(III) can be removed from solution by precipitation with sulfide or by adsorption or complexation with other metal sulfides. The performance of As(V) bio-reduction under autohydrogenotrophic conditions was investigated with batch experiments. The results showed that As(V) reduction was a biochemical process while both acclimated sludge and hydrogen were essential. Most of the reduced arsenic remained in a soluble form, although 20% was removed with no addition of sulfate, while 82% was removed when sulfate was reduced to sulfide. The results demonstrated that the reduced arsenic was re-sequestered in the precipitates, probably as arsenic sulfides. Kinetic analysis showed that pseudo first-order kinetics described the bio-reduction process better than pseudo second-order. In particular, the influences of pH and temperature on As(V) reduction by acclimated sludge under autohydrogenotrophic conditions and total soluble As removal were examined. The reduction process was highly sensitive to both pH and temperature, with the optimum ranges of pH 6.5–7.0 and 30–40°C respectively. Furthermore, Arrhenius modeling results for the temperature effect indicated that the As(V) reduction trend was systematic. Total soluble As removal was consistent with the trend of As(V) reduction.     

Novel chitosan–ethylene glycol hydrogel for the removal of aqueous perfluorooctanoic acid

It is urgent to explore an effective removal method for perfluorooctanoic acid (PFOA) due to its recalcitrant nature. In this study, a novel chitosan-based hydrogel (CEGH) was prepared with a simple method using chitosan and ethylene glycol through a repeated freezing–thawing procedure. The adsorption of PFOA anions to CEGH agreed well to the Freundlich–Langmuir model with a maximum adsorption capacity as high as 1275.9?mg/g, which is higher than reported values of most adsorbents for PFOA. The adsorption was influenced by experimental conditions. Experimental results showed that the main removal mechanism was the ionic hydrogen bond interaction between carbonyl groups (COO^?) of PFOA and protonated amine (NH⁺) of the CEGH adsorbent. Therefore, CEGH is a very attractive adsorbent that can be used to remove PFOA from water in the future.     

Pb(II) removal from water using Fe-coated bamboo charcoal with the assistance of microwaves

Bamboo charcoal(BC) was used as starting material to prepare iron-modified bamboo charcoal(Fe-MBC) by its impregnation in FeCl 3 and HNO 3 solutions simultaneously,followed by microwave heating.The material can be used as an adsorbent for Pb(Ⅱ) contaminants removal in water.The composites were prepared with Fe molar concentration of 0.5,1.0 and 2.0 mol/L and characterized by means of N 2 adsorption-desorption isotherms,X-ray diffraction spectroscopy(XRD),scanning electron microscopy coupled with energy dispersive X-ray spectrometry(SEM-EDS),Fourier transform infrared(FT-IR) and point of zero charge(pH pzc) measurements.Nitrogen adsorption analyses showed that the BET specific surface area and total pore volume increased with iron impregnation.The adsorbent with Fe molar concentration of 2 mol/L(2Fe-MBC) exhibited the highest surface area and produced the best pore structure.The Pb(Ⅱ) adsorption process of 2Fe-MBC and BC were evaluated in batch experiments and 2Fe-MBC showed an excellent adsorption capability for removal Pb(Ⅱ).The adsorption of Pb(Ⅱ) strongly depended on solution pH,with maximum values at pH 5.0.The ionic strength had a significant effect on the adsorption at pH < 6.0.The adsorption isotherms followed the Langmuir isotherm model well,and the maximum adsorption capacity for Pb(Ⅱ) was 200.38 mg/g for 2Fe-MBC.The adsorption processes were well fitted by a pseudo second-order kinetic model.Thermodynamic parameters showed that the adsorption of Pb(Ⅱ) onto Fe-MBC was feasible,spontaneous,and exothermic under the studied conditions,and the ion exchange mechanism played an significant role.These results have important implications for the design of low-cost and effective adsorbents in the removal of Pb(Ⅱ) from wastewater.     

浅析连云港市工业废水处理设施所存在的问题

根据连云港市污染物排放量的比较和污染减排任务的要求,选取COD和NH3-N 2种具有代表性的污染物,详细研究连云港市工业行业的COD和NH3-N产、排量,根据数据测算出所占排放量比重,对比重较大的饮料制造业、食品加工业和化学品原料及化学品制造业的污染治理设施进行了详细调查,发现治理设施大部分为生物接触氧化法等废水生物处理法进行有机物治理.总结了连云港市在工业废水处理设施中存在的问题,提出对策与建议.     

多目标规划在预测区域总产值-排污-水质协调解中的应用研究

以某区域水环境－经济系统为研究实例，寻求值－排污－水质综合协调解方法，寻求净收益最大时的总体规划方案。建立目标参数规划模型，寻求不同生产规模条件下的产值－排污－水质协调解，又探讨了水环境标准约束下的某化工区废水治理费用的计算方法，提出了以供决策者选择的方案。     

土壤整体质量的生态毒性评价

土壤样品采自沈阳西部污灌区 .进行了污染物 (重金属和矿物油 )含量分析和生态毒性试验 .重金属采用原子吸收分光光度仪测定 ,矿物油采用紫外分光光度计测定 .生态毒性试验分别参照国际标准组织 (ISO)和OECD指南 ,进行了植物毒性试验、蚯蚓毒性试验和蚕豆根尖微核试验 .植物试验以小麦种子发芽根伸长抑制率为试验终点 ,试验周期50h ,蚯蚓毒性试验以蚯蚓死亡率、体重增长抑制率为试验终点 ,试验周期28d .土壤中矿物油含量在145mg/kg～1121mg/kg ,重金属Cd为0.34mg/kg～1.81mg/kg .土壤对植物和蚯蚓显示不同程度的毒性效应 ,土壤的蚕豆根尖微核率明显高于对照 .种子发芽根伸长抑制率为2.0%至-35.1% ,蚯蚓死亡率为0%～40%.体重增长抑制率由14d的-2.3%～-19.4%在28d增加到-2.1%～10.7% ,蚕豆根尖微核率最高达6.62/100.研究表明 ,土壤中的污染物积累较低 ,但具有明显的生态毒性 .     

滇池富营养化特性评价

介绍了滇池水质状况,对滇池富营养化特性进行了分析和评价,并提出了对策.     

国际化学危险品分类体系简介

介绍了当前国际化学危险品的各种分类体系,对比了GHS与TDG、EU_CLP、DOT、WHMIS等对化学危险品的具体分类。有助于GHS的理解与掌握,全面推进GHS在我国的实施。     

论给水管材发展的新趋向

本文从给水管材的发展阶段、国内外给水管材的发展动向详细地阐述了我国现阶段给水管材的应用和未来发展趋向，提出了我们现在面临的问题和发展前景。     

后勤装备防腐涂层加速试验环境谱研究

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试行高校学生体质健康标准的情况分析

本文通过对我校试行高等学校《学生体质健康标准》，对04级827人的身高体重指数、分数、耐力指数、握力指数等测试结果进行统计学分析和总结评价，从而得出了对《学生体质健康标准》的几点初步认识。     

烟气脱硫副产物的综合利用

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