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 Fe2O3 and Al2O3. 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 Fe2O3. The results also showed that adsorption of As（Ⅴ） on A12O3 was not affected by chloride and nitrate anions, but slightly by Se（Ⅳ） and V（Ⅴ） ions. Unlike the adsorption of As（Ⅴ） with Fe2O3, that with Fe2O3 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 Fe2O3 and Al2O3. Compared to the other tested anions, phosphate anion was found to be the most prominent solute affecting the As（Ⅴ） adsorption with Fe2O3 and Al2O3. In general, Fe2O3 has a better performance than Al2O3 in removal of As（Ⅴ） within a water environment where multi competing solutes are present.

Evaluation of the adsorption potential of titanium dioxide nanoparticles for arsenic removal

The adsorption potential of titanium dioxide （TiO2） nanoparticles for removing arsenic from drinking water was evaluated. Pure and iron-doped TiO2 particles are synthesized via sol-gel method. The synthesized TiO2 nanoparticles were then immobilized on ordinary sand for adsorption studies. Adsorption isotherms were conducted on the synthesized nanoparticles as well as the sand coated with TiO2 nanoparticles under varying conditions of air and light, namely, the air-sunlight （A-SL）, air-light （AL）, air-dark （AD） and nitrogen-dark （ND）. X-ray diffraction （XRD） analysis showed that the pure and iron-doped TiO2 nanoparticles were in 100% anatase crystalline phase with crystai sizes of 108 and 65 nm, respectively. Adsorption of arsenic on the three adsorbents was non-linear that could be described by the Freundlich and Langmuir adsorption models. Iron doping enhanced the adsorption capacity of TiO2 nanoparticles by arresting the grain growth and making it visible light responsive resulting in a higher affinity for arsenic. Similarly, the arsenic removal by adsorption on the sand coated with TiO2 nanoparticles was the highest among the three types of sand used. In all cases, As（V） was adsorbed more compared with As（Ⅲ）. The solution pH appeared to be the most important factor in controlling the amount of arsenic adsorbed.

Synergistic Adsorption by Biomassbased Fe-Al(Hydr)oxide Nanocomposite of Fluoride and Arsenic

Fe-Al(hydr)oxide nano-/micro-particles were well grown and dispersed on a wheat straw template,which was characterized by a scanning electron microscope(SEM)with energy-dispersive X-ray spectroscopy(EDS),X-ray diffraction(XRD),and a vibrating sample magnetometer(VSM).The adsorption mechanism of the biomass-based Fe-Al(hydr)oxide nanocomposite was studied by the adsorption isotherms,which followed the Langmuir model better than the Freundlich and Temkin models.In particular,a synergistic adsorption by the mixed Fe-Al(hydr)oxide nano-/micro-particles based on the wheat straw was found,with higher maximum adsorption capacity(Q0)than that of the material containing only Fe3O4 or Al(OH)3 nano-/micro-particles,which was most obvious when the mole ratio of Fe to Al was 1:1.The degree of this unusual effect was reasonably determined by the departure between the experimental and calculated maximum adsorption capacity(Q0-Q0(cal)),which showed that the synergistic effect was most pronounced when the mole ratio of Fe to Al was approximately 1:1.The good adsorption capacity of the mixed Fe-Al(hydr)oxide nano-/micro-particles and the good dispersity by the wheat straw matrix were combined in the biomass-based Fe-Al(hydr)oxide nanocomposite.The nanocomposite material showed high adsorption capacity for both fluoride(F-)and arsenic(As(III)and As(V)),and had the advantage of magnetic separation by tuning its compositions.

Adsorption removal of roxarsone, arsenite(Ⅲ),and arsenate(Ⅴ) using iron-modified sorghum straw biochar and its kinetics

Arsenic(As)contamination in groundwater is a major problem in many countries,which causes serious health issues.In this paper,a novel method has been developed for the simultaneous removal of ROX and As(Ⅲ/Ⅴ)using the modified sorghum straw biochar(MSSB).The MSSB was characterized by X-ray diffraction,scanning electron microscopy,Fourier Transform Infrared,and Brunauer–Emmet–Teller(BET)surface area.The removal performance of MSSB for ROX,arsenite[As(Ⅲ)],and arsenate(As(Ⅴ))was investigated using batch experiments.At pH of 5,the arsenic concentration of 1.0 mg/L,adsorbent dose of 1.0 g/L,the maximum adsorptioncapacities of ROX,As(Ⅲ),and As(Ⅴ)were 12.4,5.3,and 23.0 mg/g,respectively.The adsorption behaviors were fit well with the Langmuir and the pseudo-second-order rate model.The results showed that MSSB acted as a highly effective adsorbent to simultaneously remove the composite pollution system consisted of ROX and As(Ⅲ/Ⅴ)in aqueous solutions,providing a promising method in environmental restoration applications.

Functionalized C,N-Bipyrazole Receptor Grafted onto Silica Surface for Arsenic Adsorption and Its Antibacterial Activity

The present study is based on the investigation of performance of C,N-bipyrazole receptor grafted onto silica surface (SG2P) of adsorption Arsenic (AS) from aqueous solutions. The effects of operating parameters that include pH, contact time, concentration of As and dosage of adsorbent on adsorption were accomplished. The results clearly showed that the removal efficiency of As was decreased with an increasing of As concentration, pH, and temperature, while it was continuously increasing with time and adsorbent dose. Moreover, the removal efficiency of Cr (VI) adsorption was 75% corresponding to pH;temperature (°C), initial concentration (ppm) and weight of dose (g) were 6, 25, and 0.04 respectively at 24 hours. The adsorption capacity of the synthesized sorbent (SG2P) for arsenic at pH Escherichia coli (ATCC25922) and Staphylococcus aureus (ATCC25932) were as a reference strains, while, the SG2P was able to inhibit growth only at high concentration (MIC = 1.5625 mg/ml).

Competitive and cooperative adsorption of arsenate and citrate on goethite

The fate of arsenic in natural environments is influenced by adsorption onto metal （hydr）oxides. The extent of arsenic adsorption is strongly affected by coexisting dissolved natural organic acids. Recently, some studies reported that there existed competitive adsorption between arsenate and citrate on goethite. Humic acid is known to interact strongly with arsenate by forming complexes in aqueous solution, hence it is necessary to undertake a comprehensive study of the adsorption of arsenate/citrate onto goethite in the presence of one another. The results showed that at the arsenate concentrations used in this study （0.006-0.27 mmol/L）, citrate decreased arsenate adsorption at acidic pH but no effect was observed at alkaline pH. In comparison, citrate adsorption was inhibited at acidic pH, but enhanced at alkaline pH by arsenate. This was probably due to the formation of complex between arsenate and citrate like the case of arsenate with humic acid. These results implied that the mechanism of the adsorption of arsenate and citrate onto goethite in the presence of one another involved not only competition for binding sites, but the cooperation between the two species at the watergoethite interface as well.

基于恒电容表面络合模型预测土壤中As(Ⅴ)吸附行为研究

吸附是控制As在土壤中迁移的重要过程之一,为了预测As(Ⅴ)在土壤中的吸附过程,使用恒电容表面络合模型(CCM)模拟As(Ⅴ)在土壤中的吸附行为,获取As(Ⅴ)在土壤上吸附的表面络合常数,建立土壤基本理化性质(pH、有机质、碳酸钙、无定形铁/铝/锰、总铁)与As(Ⅴ)表面络合参数的线性回归模型,以阐明As在土壤中吸附的主控因子。结果显示,As(Ⅴ)在不同类型的土壤中表现出不同的吸附特征,恒电容模型能够很好地模拟As(Ⅴ)在不同pH下的吸附特性(R^(2)为0.71~0.96),通过CCM模型拟合得到As(Ⅴ)在土壤表面的3个表面络合常数,绝大部分土壤lg K_(1)比lg K_(2)和lg K_(3)的值要大,说明As(Ⅴ)在土壤中的吸附相较于单齿络合物更偏向于形成双齿双核的络合物。As(Ⅴ)表面络合常数与土壤性质间的回归分析结果表明,As(Ⅴ)表面络合常数主要受土壤pH和无定形铁、无定形锰含量的影响。为了进一步验证上述线性模型的普适性,利用文献数据中土壤性质数据预测不同土壤上As(Ⅴ)的表面络合常数,并结合CCM模型预测了As(Ⅴ)在文献土壤中的吸附量,预测值和实测值具有很好的相关性,说明该模型具有一定的普适性。

Progress of gaseous arsenic removal from flue gas by adsorption:Experimental and theoretical calculations

Because of its high mobility and difficult capture,gaseous arsenic pollution control has become the focus of arsenic pollution control.It mainly exists in the form of highly toxic As_(2)O_(3)in the flue gas.Therefore,removing gaseous As_(2)O_(3)from flue gas is of great practical significance for arsenic pollution control.Stabilizing gaseous As_(2)O_(3)on the surface of adsorbents by physical or chemical adsorption is an effective way to reduce the content of arsenic in the flue gas and alleviate arsenic pollution.Over the past few decades,various adsorbents have been developed to capture gaseous As_(2)O_(3)in the flue gas,and their adsorption mechanisms have been studied in detail.Thus,it is necessary to review the strategies of arsenic removal from flue gas by adsorption,which can inspire further research.Based on summarizing the morphological distribution of gaseous As_(2)O_(3)in the flue gas,this review further summarizes the removal of gaseous As_(2)O_(3)by several adsorbents and the effect of temperature and the main components of the flue gas on arsenic adsorption.In addition,the mechanism of arsenic removal based on adsorption in the flue gas is discussed in depth through theoretical calculations,which is the particular focus of this review.Finally,prospects based on the present research state of arsenic removal by adsorption are proposed to provide ideas for developing effective and stable adsorbents for arsenic removal from flue gas.

煅烧水滑石同时去除废水中Sb(Ⅴ)和刚果红的性能及机制

研发能够同时有效去除重金属和有机污染物的环境材料对于工业废水绿色高效处理具有重要意义。本文采用水热法合成了镁铝水滑石(MgAl-LDH),结合高温处理的方法制备了煅烧水滑石(LDO)。在分析煅烧产物的结构和性质的基础上,运用静态批量法研究了在煅烧温度、初始质量浓度、接触时间和共存体系等条件下LDO去除Sb(Ⅴ)和刚果红(CR)的性能。结果表明,煅烧温度对于LDO去除Sb(Ⅴ)和CR的效果具有显著影响,在煅烧温度为500℃时,去除容量分别可达426.4 mg/g和1516.2 mg/g,这是因为高温煅烧后LDO的比表面积和孔隙体积增大,LDO与水溶液接触重建层状结构后具有较强的捕获Sb(Ⅴ)和CR阴离子污染物插入层间的能力;LDO对Sb(Ⅴ)和CR的去除容量在前3 h内增加迅速,之后缓慢增加,在6 h左右时达到吸附平衡,这是因为开始时LDO具有大量活性位点,随着接触时间的延长,Sb(Ⅴ)和CR被积累吸附在其表面并占据了部分活性位点,吸附质需要克服更大的空间位阻才能与吸附剂反应,因此吸附速度变慢,直至LDO表面的吸附位点被完全占据,吸附达到平衡;去除容量随着初始质量浓度的升高逐渐增加,这是因为较高的浓度使吸附质更容易突破液相与固体吸附剂表面间的传质阻力;在共存体系下LDO对Sb(Ⅴ)和CR的去除容量略低于单一体系,这可能与Sb(Ⅴ)和CR竞争LDO浸出的液相Mg^(2+)以及LDO表面吸附位点有关。LDO主要依靠静电引力、络合作用、结晶沉淀以及MgAl-LDH的记忆效应实现对Sb(Ⅴ)和CR的同时高效去除。

Practical performance and its efficiency of arsenic removal from groundwater using Fe-Mn binary oxide

A treatment unit packed by granular adsorbent of Fe-Mn binary oxide incorporated into diatomite （FMBO（1：1）-diatomite） was studied to remove arsenic from anaerobic groundwater without any pre-treatment or post-treatment. The raw anaerobic groundwater containing 35-45 μg/L of arsenic was collected from suburb of Beijing. Arsenic（Ⅲ） constituted roughly 60%-80% of the total arsenic content. Approximately 7,000 bed volumes （ratio of effluent volume to adsorbent volume） treated water with arsenic concentration below 10 μg/L were produced in the operation period of four months. The regeneration of FMBO（1：1）-diatomite had been operated for 15 times. In the first stage, the regeneration process significantly improved the adsorption capacity of FMBO（1：1 ）-diatomite. With increased loading amount of Fe-Mn binary oxide, the adsorption capacity for arsenic decreased 20%-40%. Iron and manganese in anaerobic groundwater were oxidized and adsorptive filtrated by FMBO（1 ： 1）-diatomite efficiently. The final concentrations of iron and manganese in effluents were nearly zero. The continued safe performance of the treatment units proved that adsorbent FMBO（1：1）- diatomite had high oxidation ability and exhibited strong adsorptive filtration.

Effect of ionic strength on adsorption of As(Ⅲ) and As(V) on variable charge soils

The study was to investigate the adsorption behavior of arsenite （As（HI）） and arsenate （As（V）） on two variable charge soils, i.e., Haplic Acrisol and Rhodic Ferralsol at different ionic strengths and pH with batch methods. Results indicated that the amount of As（HI） adsorbed by these two soils increased with increasing solution pH, whereas it decreased with increasing ionic strength under the acidic condition. This suggested that As（Ⅲ） was mainly adsorbed on soil positive charge sites through electrostatic attraction under the acidic condition. Moreover, intersects of As（Ⅴ） adsorption-pH curves at different ionic strengths （a characteristic pH） are obtained for both soils. It was noted that above this pH, the adsorption of As（Ⅴ） was increased with increasing ionic strength, whereas below it the reverse trend was true. Precisely the intersect pH was 3.6 for Haplic Acrisol and 4.5 for Rhodic Ferralsol, which was near the values of PZSE （soil point of zero salt effect） of these soils. The effects of ionic strength and pH on arsenate adsorption by these soils were interpreted by the adsorption model. The results of zeta potential suggested that the potential in adsorption plane becomes less negative with increasing ionic strength above soil PZSE and decreases with increasing ionic strength below soil PZSE. These results further supported the hypothesis of the adsorption model that the potential in the adsorption plane changes with ionic strength with an opposite trend to surface charge of the soils. Therefore, the change of the potential in the adsorption plane was mainly responsible for the change of arsenate adsorption induced by ionic strength on variable charge soils.

Arsenic in Drinking Water and Its Removal

Superfluous arsenic in drinking water can do harm to human health. In this paper, a broad overview of the available technologies for arsenic removal has been presented on the basis of literature survey. The main treatment methods included coagulation-sedimentation, adsorption separation and ion exchange, membrane technique, which have both advantages and disadvantages. It concluded that the selection of treatment process should be site specific and prevailing conditions and no process can serve the purpose under diverse conditions as each technology has its own limitations. In order to gain good results, some methods should be improved.

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.

Kinetics, thermodynamics, and equilibrium of As(Ⅲ),Cd(Ⅱ), Cu(Ⅱ) and Pb(Ⅱ) adsorption using porous chitosan bead-supported MnFe_(2)O_(4) nanoparticles

A novel porous nanocomposite,cross-linked chitosan and polyethylene glycol(PEG) bead-supported MnFe_(2) O_(4) nanoparticles(CPM),was developed as an efficient adsorbent to remove metalloid(As(Ⅲ))and heavy metals(Cd(Ⅱ),Cu(Ⅱ),and Pb(Ⅱ)).The characteristics of CPM showed a porous structure,well dispersed MnFe_(2) O_(4),and several of hydroxyl and amino groups(-OH,-NH_(2)).Batch experiments demonstrated that the best adsorption property of As(Ⅲ),Cd(Ⅱ),Cu(Ⅱ),and Pb(Ⅱ) was achieved within 8 h with maximum adsorption capacities of 9.90,9.73,43.94,and 11.98 mg/g,respectively.Competitive and synergistic effects(particularly precipitation) were included in the co-adsorption mechanism of As(Ⅲ) and heavy metals.Thereinto,As(Ⅲ) was partly oxidized by MnFe_(2) O_(4) to As(V),and both were coordinated on MnFe_(2) O_(4) nanoparticles.Pb(Ⅱ) could also bind to MnFe_(2) O_(4) by ion exchange and electrostatic attraction.Furthermore,Cd(Ⅱ) and Cu(Ⅱ) tended to be coordinated on chitosan.Therefore,CPM can serve as a remediation material for water and soil co-contaminated with As(Ⅲ) and heavy metals.

Removal of Arsenic(V) from Aqueous Solutions by Lanthanum-loaded Zeolite

A new adsorption process for the removal of As（V） ion from aqueous solutions is studied in this paper using lanthanum-loaded zeolite. The removal efficiency of different adsorbents, activated alumina and activated carbon are obtained in the study for comparison. The results show that lanthanum-loaded zeolite is an effective adsorbent for the removal of As（V） from aqueous solutions. Then, the pH effect and regeneration of modified zeolite on the As（V） removing efficiency are also assessed. It functions with a wide range of pH （2-8）. After adsorption, zeolite adsorbed with As（V） ions can be regenerated successfully with 1 M NaOH. Based on the data obtained, an adsorption mechanism and the possible complex structure are tentatively presented. Compare to other adsorbents, easy availability of this adsorbent, excellent adsorption capacity, wide optimum pH range, and regeneration are expected to be utilized in practical operations.

Experimental Study on the Removal of Arsenic in Waste Water from Semiconductor Manufacturing

An effective and economic process for removing arsenic in waste water which is acuminating in the process of etching, cutting and washing in semiconductor industry has been developed in this paper. The proposed technique of arsenic removal is as follows: first pretreatment step is to oxidize arsenite to arsenate by potas-sium permanganate, second key step is precipitation based on arsenic compound solubility with ferric sulfate and slaked lime under pH adjustment, and the last complementary step is followed by the adsorption of the bentonite with enhanced by activated carbon and organic adsorbent. Experimental results show that under the optimal condition the removal efficiency of arsenic in the waste water is better than 99.99%, or the concen-tration of arsenic is from its original 100mg/l reduced to less than 10µg/l accordingly.

Effect of Fe_(3)O_(4) nanoparticles on magnetic xerogel composites for enhanced removal of fluoride and arsenic from aqueous solution

Fe_(3)O_(4)magnetic xerogel composites were prepared by polycondensation of resorcinol(R)-formaldehyde reaction via a sol-gel process in an aqueous solution through varying the molar ratio of Fe_(3)O_(4)nanoparticles(MNPs),catalyst(C),and water(W)content.MNPs were obtained by co-precipitation(MC),oxidation of iron salts(MO),or solvothermal synthesis(MS).Both MNPs and magnetic xerogels were examined regarding the performance of arsenic and fluoride removal in a batch system.The MC-based MNPs had higher adsorption capacities for both fluoride(202.9 mg/g)and arsenic(3.2 mg/g)than other MNPs in optimum conditions.The X-ray diffraction,Fourier transform infrared spectroscopy,and energy-dispersive X-ray spectroscopy confirmed that Fe was composed into the polymeric matrix of magnetic xerogels that contained 0.59%-4.42%of Fe with a molar ratio of MNPs(M)to R between 0.01 and 0.10.With low R/C and optimum M/R ratios,an increase in the surface area of magnetic xerogels affected the fluoride and arsenic adsorption capacities.The magnetic xerogel composites with the MC-based MNPs prepared at a fixed R/C ratio(100)and at different R/W(0.05-0.06)and M/R(0.07-0.10)ratios had a high arsenic removal efficiency of 100%at an As(V)concentration of 0.1 mg/L and pH of 3.0.The maximum adsorption capacities of magnetic xerogels were approximately five times higher than those of the xerogels without MNP composites.Therefore,Fe_(3)O_(4)nanoparticles enhanced the adsorption of arsenate and fluoride.The variations of alkaline catalyst and water content significantly affected the resulting properties of textural and surface chemistry of magnetic xerogel composites.

Effect of chemical activation process on adsorption of As(V) ion from aqueous solution by mechano-thermally synthesized zinc ferrite nanopowder

Nanostructured ZnFe2O4 was synthesized by the heat treatment of a mechanically activated mixture of ZnO/α-Fe2O3.X-ray diffraction(XRD)and differential thermal analysis(DTA)results demonstrated that,after 5 h of the mechanical activation of the mixture,ZnFe2O4 was formed by heat treatment at 750°C for 2 h.To improve the characteristics of ZnFe2O4 for adsorption applications,the chemical activation process was performed.The 2 h chemical activation with 1 mol·L?1 HNO3 and co-precipitation of 52%?57%dissolved ZnFe2O4 led to an increase in the saturated magnetization from 2.0 to 7.5 emu·g?1 and in the specific surface area from 5 to 198 m2·g?1.In addition,the observed particle size reduction of chemically activated ZnFe2O4 in field emission scanning electron microscopy(FESEM)micrographs was in agreement with the specific surface area increase.These improvements in ZnFe2O4 characteristics considerably affected the adsorption performance of this adsorbent.Adsorption results revealed that mechano-thermally synthesized ZnFe2O4 had the maximum arsenic adsorption of 38%with the adsorption capacity of 0.995 mg·g?1 in a 130 mg·L?1 solution of As(V)after 30 min of agitation.However,chemically activated ZnFe2O4 showed the maximum arsenic adsorption of approximately 99%with the adsorption capacity of 21.460 mg·g?1 under the same conditions.These results showed that the weak adsorption performance of mechano-thermally synthesized ZnFe2O4 was improved by the chemical activation process.

磷石膏基吸附剂的制备及其对As(Ⅴ)的吸附性能试验研究

研究了用氧化钙(CaO)改性磷石膏(PG)制备吸附剂m-CaO-PG,并用于从废水中吸附去除As(Ⅴ),采用Design-Expert软件以响应面法中的Box-Behnken程序优化m-CaO-PG制备工艺,考察了球磨转速、球磨时间和物料质量比对m-CaO-PG吸附As(Ⅴ)的影响。结果表明:制备m-CaO-PG的最佳条件为球磨转速200 r/min,物料质量比6/4,球磨时间4 h;m-CaO-PG对As(Ⅴ)的最大吸附量为37.75 mg/g;吸附过程中产生了Ca_(3)(AsO_(4))_(2)和CaHAsO_(4)·2H_(2)O新物相,新物相中增加了羟基自由基;m-CaO-PG有更大表面积和孔隙体积,吸附去除As(Ⅴ)效果较好。