改性粉煤灰处理低浓度含砷含氨氮废水

在冶金和采矿等行业里,排放废水中的砷和氨氮均存在不同程度的超标。本实验采用粉煤灰对砷和氨氮进行深度处理。考察了不同改性方法对粉煤灰除砷和氨氮的处理效果。实验结果表明： NaOH＋FeCl3复合改性的粉煤灰对两种污染物都有较好的去除效果,废水中含砷2 mg/L,含氨氮50 mg/L,复合改性粉煤灰的投加量为20 g/L,废水pH为6,搅拌1 h,砷和氨氮的去除率分别达到83.33%和82.48%,出水满足《污水综合排放标准》（GB8978-1996）中砷和氨氮的排放要求。     

结晶型砷酸镍的溶解性

结晶型砷酸镍的溶解性用溶液中的Ni和As的浓度来表征.TCLP实验结果表明Ni和As在溶液中的浓度随着实验重复次数的增加而显著降低,说明自制结晶型砷酸镍中含有部分非晶态物质.长期溶解性实验证明结晶型砷酸镍的溶解在15 d后达到平衡,并且随着pH值升高溶液中Ni和As浓度降低,在pH 9时达到最低的48 mg•L^-1 As和0.2 mg•L^-1 Ni,砷酸镍中的As和Ni在pH 3和pH 4时按分子式理论值n(Ni)∶n(As)=1.5同步溶解,而由于Ni(OH)₂的生成,在高pH值溶液中的n(Ni)∶n(As)远低于理论值1.5.实验结果表明本研究合成的结晶型砷酸镍比Nishimura等的更稳定,具有更低的溶解性.     

利用硫化亚铁从污酸废水中回收砷

针对铜冶炼过程中产生的高浓度的含砷酸性废水,研究了一种新的处理方法：采取两段操作的方式,一段利用硫化亚铁作为除砷剂,使砷生成硫化砷沉淀去除。二段利用石灰调节pH,进一步除砷。通过两段能够使污酸废水在处理后达到国家排放标准,同时能够回收废水中的砷。研究了投药量、pH、反应时间和曝气时间等因素对除砷率的影响。实验结果表明：在硫化亚铁的投加量为理论计算所需摩尔质量的2倍时,一段室温下反应3h,二段曝气反应30min后,水中砷含量由进水时的6240 mg·L^-1降低至0.5 mg·L^-1以下,水中砷的平均去除率可以达到99.9%以上,渣中砷含量可以达到15% 以上。     

排管水pH值的连续测量

用于冷却硫酸的排管水、常因管道漏酸、使排管水酸度达pH1～2。为了无害排放和工业用水的循环使用,需要在含有酸的排管水中加入NaOH或其他碱溶液进行中和,使其pH值达到6～8。如以NaOH做中和剂,其反应方程式为     

pH调整剂对含砷酸性废水中氧化Fe（Ⅱ）共沉淀固砷行为的影响

双氧水催化氧化Fe（Ⅱ）共沉淀砷的过程中,采用不同的pH调整剂调节溶液的pH,研究了不同的pH调整剂对废水中砷沉淀效果及沉淀渣性质的影响。结果表明：采用Na₂CO₃和CaO作为pH调整剂时有利于废水中砷的脱除,生成的共沉淀渣中砷主要是以无定形的非晶态块状颗粒形式存在的;使用Na₂CO₃作为pH调整剂时最有利于沉淀渣颗粒的长大,所得沉淀渣粒径最大,但是砷渣的稳定性最差,更容易从渣中释放出砷;采用CaO获得的沉淀渣中由于CaSO₄棒状颗粒的存在,渣的粒径相对较小,但砷的存在形式最为稳定,固砷效果最好。     

去除试剂硫酸铜中砷的新方法

硫酸铜在化学工业等生产中有广泛的应用。但其中的砷含量较高时,不能用于饲料工业中。我国国家标准规定,饲料级硫酸铜中的砷含量不能超过0.0005%。根据沉淀溶度积原理,利用吸附剂吸附分散在溶液中的沉淀质点,并使之凝聚下来以除去砷杂质。实验方法是:取一定量的硫酸铜溶液,用 NH_3水或 NaOH 调节 pH■5,加活性炭     

氢氧化铁胶体对砷吸附行为的初步研究

研究了pH值、铁与砷的量比和初始砷浓度等因素对用氢氧化铁胶体吸附去除砷的影响,确定了最佳吸附条件。研究结果表明,在初始As(Ⅴ)或As(Ⅲ)浓度为0.1mmol/L条件下,去除As(Ⅴ)的最佳pH值为4～8,去除As(Ⅲ)最佳pH值为6～9;在初始As(Ⅴ)浓度为0.5mmol/L条件下,去除As(Ⅴ)的最佳pH值为5～7,吸附后溶液中砷含量低于0.5mg/L,达到了《污水综合排放标准(GB8978-1996)》中工业废水最高容许排放总砷浓度一级标准。通过等温吸附试验的研究,得出了As(Ⅴ)和As(Ⅲ)的饱和吸附容量分别为0.4971mol/kg和0.3068mol/kg。     

预氧化-铁盐沉淀法处理高浓度含砷废水的试验研究

对某砷化镓半导体企业生产过程中产生的高浓度含砷(As)废水,采用过氧化氢(H2 O2)预氧化结合氯化铁(FeCl3)沉淀法进行处理.研究确定了H2O2的投加量,并考察了Fe与As物质的量比、pH值和反应时间等试验条件对砷去除效果的影响.结果表明,当30％H2 O2用量为1.5 mL/L,Fe与As物质的量比为2.5,pH值为8.0,反应时间为2 h时,废水中的总砷浓度可从884 mg/L降低至0.164 mg/L,达到项目环评要求的0.2 mg/L的排放标准.     

从生物氧化提金废液中制备砷酸铜

在前期实验的基础上,针对生物氧化提金废液砷铁分离后的砷浸出液,探讨了以砷酸铜形式回收砷的热力学和工艺参数,绘制了Cu-As-H2O系的电位-pH图,对砷酸铜制备过程进行了热力学分析,考察了pH值、温度、搅拌速度对砷回收率的影响,得到制备砷酸铜的最佳工艺条件为pH=4.0、温度50℃、搅拌速度500r/min.在该工艺条件下,制得了结构式为Cu5H2(AsO4)4的砷酸铜,砷回收率达95.10%以上.     

聚硅酸氯化铝铁处理含砷废水的实验研究

对聚硅酸氯化铝铁混凝处理含砷废水进行了研究。考察了混凝剂用量,(Fe Al)/SiO2物质的量比,碱化度对除砷率的影响。实验结果表明(Fe Al)/SiO2=5∶1,B=0.1时,在pH值7.0,投加量为120 mg/L的条件下,聚硅酸氯化铝铁除砷率达90.5%。实际水样处理后的水质能够达到废水中砷的排放标准。并且通过红外光谱分析讨论了混凝除砷机理。     

三价铁离子浓度对As(V)-Fe(II)-Fe(III)体系沉淀臭葱石的影响

在常压、95℃、初始pH=1.5的条件下,研究了As(V)–Fe(II)–Fe(III)体系中初始Fe(III)浓度对砷的去除率和臭葱石合成的影响。结果表明,溶液中初始Fe(III)/As(V)摩尔比为0时,沉淀产物为结晶度良好的臭葱石,但砷的去除率仅为24.3%,沉淀浸出砷浓度高于国标规定的浓度限值5 mg/L。溶液中初始Fe(III)/As(V)摩尔比大于0时,在升温过程中生成了无定形砷酸铁,当初始Fe(III)/As(V)摩尔比不超过1.6时,砷酸铁反应8 h后转化为臭葱石;随初始Fe(III)/As(V)摩尔比增大,砷的去除率增大,臭葱石沉淀的结晶度降低、浸出砷浓度降低;其中,初始Fe(III)/As(V)摩尔比为0.8和1.6时,臭葱石沉淀的浸出砷浓度低于5 mg/L,适合安全堆存。当初始Fe(III)/As(V)摩尔比大于1.6时,无定形砷酸铁反应8 h仍不能转化成臭葱石,砷的去除率降低,沉淀浸出砷浓度超标,不适合安全堆存。     

Arsenic(V) removal from enargite leach solutions by precipitation of magnesium ammonium arsenate

This study investigated a potential method for the removal of arsenic from enargite leach solution containing 5.86 g/L As(V) by precipitation of magnesium ammonium arsenate (MAA). The experimental results showed the As(V) concentration can be reduced to 1.8 mg/L under the optimum conditions. The molar ratio NH₄/Mg/As in precipitates formed at different pH values was checked by wet chemical analysis, indicating that some of by-products such as Mg₃(AsO₄)₂, Mg(OH)₂, and MgHAsO₄ will be formed at the solution pH above or below pH 9.5. Notably, this study indicated MAA has a better ability for arsenic removal than magnesium arsenate. The precipitates also were characterized by XRD and SEM.     

Physicochemical Characterization of Granular Ferric Hydroxide (GFH) for Arsenic(V) Sorption from Water

Abstract

Physical and chemical characterization of granular ferric hydroxide (GFH) [e.g., scanning electron micrographs (SEM), X‐ray diffraction (XRD) analysis, Brunauer‐Emmett‐Teller (BET) and Langmuir surface area measurements, pore size distribution, pH titration, and zeta potential measurements] were conducted to determine its performance as an adsorbent for trace arsenic(V) removal. Speciation diagrams for arsenate and phosphate were produced for the present system. The equilibrium adsorption isotherms were measured over initial arsenate concentrations ranging from 100–750 µg/L and the pH range of 4–9. The adsorption of arsenate was found to decrease as the pH of the solution was increased, thus giving the optimal adsorption of arsenate onto GFH at pH 4. Adherence to the Langmuir isotherm was found at all pHs for the arsenate adsorption. The competitive effect of phosphate on the uptake of arsenate at pH 4 by GFH was investigated, outlining the greater affinity of GFH for arsenate adsorption compared to phosphate. The kinetic performance of GFH was assessed and the results were analyzed by applying a particle diffusion model.     

Arsenic adsorption on Ti‐pillared montmorillonite

BACKGROUND: Arsenic pollution in drinking water has been found in most countries. Arsenate (As(V)) and arsenite (As(III)) are two major forms of inorganic arsenic species, and the latter is the more toxic. The removal of arsenic ions from water has attracted increased attention, and therefore further understanding and development of techniques for removal of arsenic ions are required. RESULTS: Adsorption of arsenate and arsenite from aqueous solutions using Ti‐pillared montmorillonite (Ti‐MMT) was investigated as a function of contact time, pH, temperature, coexisting ions, and ionic strength. The adsorption of both arsenate and arsenite were temperature and pH dependent, indicating different adsorption mechanisms. The effect of coexisting ions on the adsorption was also studied and, among the ions investigated, only phosphate had a noticeable influence on the adsorption of arsenate, while the effect of other ions was negligible. A pseudo‐second‐order chemical reaction model was obtained for both arsenate and arsenite; adsorption isotherms of arsenate and arsenite fitted the Langmuir and Freundlich isotherm models well. X‐ray diffraction (XRD) and X‐ray photoelectron spectroscopy (XPS) were used to study the nature of surface elements before and after adsorption. CONCLUSIONS: This work demonstrates that Ti‐pillared montmorillonite is an efficient material for the removal of arsenate and arsenite from aqueous solutions. Experimental parameters such as contact time, solution pH, temperature, initial concentration, coexisting ions, and ionic strength have been optimized. Copyright © 2010 Society of Chemical Industry     

砷铁渣中砷酸铁的热力学分析及热分解试验

利用铁盐法处理某铅冶炼工业含砷废水,得到砷质量分数为10%的砷铁渣,物相分析表明砷与铁在渣中以砷酸铁的形态存在。据热力学分析,砷酸铁化合物在1600℃以下不会热分解,表明其热力学性质稳定;而在有添加剂碳的情况下,砷酸铁的热分解温度大大降低。试验结果表明:在1200℃条件下,静态焙烧5h,砷酸铁砷的挥发率在90%以上,铁富集10%以上。     

高砷烟道灰预处理水浸液中锌砷分离

对经热水浸出的高砷烟道灰水浸液进行锌砷分离,基于单独使用Fe2(SO4)3和CaO除砷的实验结果,提出了Fe2(SO4)3-CaO耦合分离锌砷工艺. 结果表明,在溶液pH=2、摩尔比H2O2/As3+ 1.3:1, Fe3+/As5+ 1:1.5, Ca2+/As5+ 1.5:1及反应温度70℃、反应时间1.5 h的条件下,砷脱除率超过80%,锌没有损失,实现了锌砷高效分离.     

臭氧氧化合成臭葱石除砷

用臭氧发生器产生的臭氧氧化模拟酸性含砷废水,在95℃下加热反应7 h合成臭葱石,考察了Fe(II)氧化速率及溶液初始pH值对砷去除率及臭葱石合成的影响. 结果表明,提高Fe(II)氧化速率及增大初始pH值均可促进As沉淀. 初始pH为2.0时通入臭氧,溶液中As的最终去除率可达89.64%,反应所得臭葱石颗粒尺寸较大、结晶良好.     

次氯酸钠氧化与铁盐沉淀组合处理废水中的草甘膦

采用次氯酸钠氧化与铁盐沉淀组合工艺处理草甘膦模拟废水,总磷去除率大于99%,对草甘膦废水的处理有较好的应用参考价值。实验结果表明,在次氯酸钠溶液投加量为1.5 mL/L,反应pH为7,反应时间1 h的条件下,草甘膦的降解率为96.77%,无机磷的转化率为85.66%;次氯酸钠溶液氧化后再投加n(Fe~(3+))∶n(P)为1.2∶1的铁盐,沉淀pH为5,可将溶液中转化的无机磷及剩余的草甘膦沉淀去除,总磷去除率大于99%。推测次氯酸钠氧化降解草甘膦的产物为肌氨酸和磷酸。     

Nanofiltration Membrane Process for the Removal of Arsenic from Drinking Water

The removal of arsenic from drinking water by nanofiltration membranes was investigated. Experiments were conducted with tap water to which arsenate and arsenite were added. Two types of nanofiltration membranes, i.e., NF‐90 and NF‐200, have been tested. The effect of various operating conditions, e.g., applied pressure, feed concentration, pH and temperature, were also investigated. The pH and arsenic concentration in the feed and the operating temperature are found to be decisive factors in determining the arsenic concentration remaining in the permeate. The level of removal of As(V) was higher than 98 % for both membranes, but that of As(III) was much lower. It can be concluded that by controlling the operating parameters, source water containing As(V) may be recovered as drinking water to EPA maximum contaminant level quality standards, but that water containing As(III) must undergo a pre‐oxidation treatment before passing through the nanofiltration membrane in order to maintain drinking water quality.     

三氯化铁除砷的工艺研究

为了减少铁盐除砷过程中产生的危险废渣的数量,研究了三氯化铁作为除砷剂处理砷(Ⅲ)和砷(Ⅴ)废水的工艺条件,主要包括pH值、铁砷摩尔比(nFe/As)、反应时间等.结果表明,用三氯化铁处理含砷(Ⅲ)1647.8 mg·L-1废水的最佳工艺条件为:pH=9、反应时间1h、nFe/As=2；处理含砷(Ⅴ) 3697.2 mg· L-1废水的最佳工艺条件为:pH=8、反应时间1h、nFe/As=2.此外,阳离子型絮凝剂PAM209cc适合于铁砷沉淀物的沉降,对砷(Ⅲ)废水和砷(Ⅴ)废水的最佳投加量分别为40 mL· L-1、20 mL· L-1.