Cascade sulfidation and separation of copper and arsenic from acidic wastewater via gas-liquid reaction

Copper and arsenic in acidic wastewater were separated by cascade sulfidation followed by replacement of arsenic in theprecipitates by copper in the solution which was realized by recycling precipitates obtained in the first stage into the initial solution.The effects of reaction time,temperature and H2S dosage on copper and arsenic removal efficiencies as well as the effects of solid-toliquidratio,time and temperature on the replacement of arsenic by copper were investigated.With20mmol/L H2S at50°C within0.5min,more than80%copper and nearly20%arsenic were precipitated.The separation efficiencies of copper and arsenic werehigher than99%by the replacement reaction between arsenic and copper ions when solid-to-liquid ratio was more than10%at20°Cwithin10min.CuS was the main phases in precipitate in which copper content was63.38%in mass fraction.

Reactive Crystallization of Calcium Sulfate Dihydrate from Acidic Wastewater and Lime

The present work focused on the recycle of the sulfate and the metal ions from acidic wastewater dis charged by nonferrous metallurgical industry. The effects of the temperature, the reactant concentration, the stirring speed and the metal ions on the reactive crystallization process of calcium sulfate between sulfuric acid and lime were systematically investigated. The morphology of the precipitated crystals evolved from plateletlike and nee dlelike shape to rodlike shape when the temperature was increased from 25 to 70 ℃. An increase in the agglom.

Selective recovery of Cu(II) from strongly acidic wastewater by zinc dimethyldithiocarbamate: Affecting factors, efficiency and mechanism

The selective recovery of copper from strongly acidic wastewater containing mixed metal ions remains a significant challenge.In this study,a novel reagent zinc dimethyldithiocarbamate(Zn(DMDC)_(2))was developed for the selective removal of Cu(II).The removal efficiency of Cu(II)reached 99.6%after 120 min reaction at 30°C when the mole ratio Zn(DMDC)_(2)/Cu(II)was 1:1.The mechanism investigation indicates that the Cu(DMDC)_(2) products formed as a result of the displacement of Zn(II)from the added Zn(DMDC)_(2) by Cu(II)in wastewater,due to the formation of stronger coordination bonds between Cu(II)and the dithiocarbamate groups of Zn(DMDC)_(2).Subsequently,we put forward an innovative process of resource recovery for strongly acidicwastewater.Firstly,the selective removal of Cu(II)fromactualwastewater using Zn(DMDC)_(2),with a removal efficiency of 99.7%.Secondly,high-value CuO was recovered by calcining the Cu(DMDC)_(2) at 800°C,with a copper recovery efficiency of 98.3%.Moreover,the residual As(III)and Cd(II)were removed by introducing H_(2)S gas,and the purified acidic wastewater was used to dissolve ZnO for preparation of valuable ZnSO_(4)·H_(2)O.The total economic benefit of resource recovery is estimated to be 11.54$/m^(3).Accordingly,this study provides a new route for the resource recovery of the treatment of copper-containing acidic wastewater.

Removal of Ni(Ⅱ) from strongly acidic wastewater by chelating precipitation and recovery of NiO from the precipitates

Strongly acidic wastewater produced in nonferrous metal smelting industries often contains high concentrations of Ni(Ⅱ), which is a valuable metal. In this study, the precipitation of Ni(Ⅱ) from strongly acidic wastewater using sodium dimethyldithiocarbamate(DDTC) as the precipitant was evaluated. The effects of various factors on precipitation were investigated, and the precipitation mechanism was also identified. Finally, the nickel in the precipitates was recovered following a pyrometallurgical method. The results show that, under optimised conditions(DDTC:Ni(Ⅱ) molar ratio = 4:1;temperature = 25 ℃), the Ni(Ⅱ) removal efficiency reached 99.3% after 10 min. In strongly acidic wastewater, the dithiocarbamate group of DDTC can react with Ni(Ⅱ) to form DDTC –Ni precipitates. Further recovery experiments revealed that high-purity Ni O can be obtained by the calcination of DDTC –Ni precipitates, with the nickel recovery efficiency reaching 98.2%. The gas released during the calcination process was composed of NO_(2), CS_(2), H_(2)O, CO_(2), and SO_(2). These results provide a basis for an effective Ni(Ⅱ) recovery method from strongly acidic wastewater.

Clean and effective removal of Cl(-I)from strongly acidic wastewater by PbO_(2)

Recycling strongly acidic wastewater as diluted H_(2)SO_(4) after contaminants contained being removed was previously proposed,however,Cl(-I),a kind of contaminant contained in strongly acidic wastewater,is difficult to remove,which severely degrades the quality of recycled H_(2)SO_(4).In this study,the removal of Cl(-I)using PbO_(2) was investigated and the involved mechanisms were explored.The removal efficiency of Cl(-I)reached 93.38%at 50℃ when PbO_(2)/Cl(-I)mole ratio reached 2:1.The identification of reaction products shows that Cl(-I)was oxidized to Cl_(2),and PbO_(2) was reduced to PbSO_(4).Cl_(2) was absorbed by NaOH to form NaClO,which was used for the regeneration of PbO_(2) from the generated PbSO_(4).Cl(-I)was removed through two pathways,i.e.,surface oxidation and•OH radical oxidation.•OH generated by the reaction of PbO_(2) and OH−plays an important role in Cl(-I)removal.The regenerated PbO_(2) had excellent performance to remove Cl(-I)after six-time regeneration.This study provided an in-depth understanding on the effective removal of Cl(-I)by the oxidation method.

弱酸性蓝AS 染料排放的废盐制碳基吸附剂及利用

将染料弱酸性蓝AS(AS)生产排放的含盐废水喷雾干燥后制成废盐,再将其有机污染物煅烧制备成类活性炭吸附剂(LAC),用于AS染料生产过程中产生的洗涤废水的吸附脱色净化,同时回收粗盐NaCl可循环用于AS工业生产的盐析过程。对LAC进行吸附过程动力学、热力学研究,并研究AS染料废水溶液初始浓度、温度及pH对吸附性能的影响。在40 mg/L的AS染料废水中,温度为318 K的条件下,平衡吸附量为29.22 mg/g。在酸性及温度较高时吸附能力较强。Langmuir等温线方程能更好拟合吸附实验结果。另外,采用一锅混合法,添加四水合乙酸镁对LAC进行改性,改性后的吸附剂LACMg0.75比表面积较LAC提升了近5倍,饱和吸附量能够达到550.02 mg/g,较LAC提升了接近20倍。

铝粉还原污酸中砷新工艺研究

由于硫化精矿中砷含量越来越高,致使烟气处理过程产生的污酸中砷含量也越来越高,同时污酸中含有铜、铁等有价金属。目前污酸除砷方法多以除砷为目的,形成的含砷渣属于危废,还需要二次处理。本研究研发了还原除砷新工艺,首先向污酸中加入硫化砷渣进行脱铜预处理并回收铜,然后用铝粉还原脱铜后液中的砷回收砷,最后向脱砷液中加入硫酸钾回收铝,还原后液回收还原剂后采用两段中和法处理。试验研究结果表明,在加入铜离子摩尔量1.1倍的硫化砷渣、反应温度85℃、反应时间3 h的条件下,污酸中的铜含量由2000 mg/L降至196 mg/L,硫化铜渣返熔炼配料系统;在还原温度70℃、还原时间2 h,还原剂用量1.8倍的条件下,砷的还原率大于96%,还原后液中的砷含量低于300 mg/L,得到的砷渣品位大于95%,可用于后续制备高品位单质砷;在硫酸钾用量1.1倍、反应温度常温、反应时间2 h的条件下,溶液含铝3.6 g/L,得到的明矾可达到《工业硫酸铝钾》(HG/T2565—2007)一等品标准。该方法除砷效果好,且能将污酸中的砷转变为具有经济价值的砷产品,还不会产生硫化氢气体,具有应用推广价值。

粉煤灰负载纳米FeS处理酸性含铬废水动态试验

针对矿区生态环境受酸性含铬废水污染严重的问题,采用超声沉淀法制备了粉煤灰负载纳米FeS吸附材料(nFeS-F)。并以粉煤灰、nFeS-F为填料分别构造1^(#)、2^(#)动态柱,进行酸性含铬废水动态处理试验,通过XRD、SEM、TEM、XPS对粉煤灰、nFeS-F进行表征,探究粉煤灰和nFeS-F处理酸性含铬废水的规律性、长效性和去除机理。结果表明:在进水Cr(Ⅵ)浓度为100 mg/L条件下,动态柱运行28 d内,1^(#)柱对Cr(Ⅵ)和总铬的平均去除率分别为42.86%和36.65%;2^(#)柱对Cr(Ⅵ)和总铬的平均去除率分别为70.74%和53.12%,至试验结束时,1^(#)柱和2^(#)柱的pH分别为5.50和6.38。通过nFeS-F的XRD、XPS表征分析表明,Cr(Ⅵ)被还原为Cr(Ⅲ),并以氢氧化物和硫化物沉淀的形式固定在nFeS-F的表面上。nFeS-F对Cr(Ⅵ)表现出优异的吸附性能,该研究可为处理酸性含铬废水提供一定的技术参考。

铁离子配位聚丙烯酸基芬顿催化纤维的制备及其性能

为改善聚丙烯酸(PAA)纤维的性能,在湿法纺丝过程中基于铁离子配位反应成功制备了可拉伸PAA初生纤维,利用后拉伸以及热定型工艺优化纤维性能,并探究其作为Fenton催化剂在染料废水处理领域的应用。结果表明:相较硫酸铁盐,氯化铁盐配位的PAA纤维具有更为优异的力学性能和尺寸稳定性;后拉伸和热定型工艺可显著提高PAA纤维的力学性能和催化活性,并抑制铁离子的流失,拉伸20倍且在130℃定型的纤维断裂强度为1.42 cN/dtex,与未拉伸纤维相比提高了914.3%,且可在3 min内脱色90%以上的亚甲基蓝(MB),循环使用40次未出现脱色率衰减现象。

赤泥用于酸性含锰废水中锰的净化研究

采用还原焙烧-磁选预处理赤泥,得到非磁性物;非磁性物经煅烧、盐酸溶出后加入饱和偏铝酸钠聚合剂聚合后过滤、熟化制备聚合氯化铝(PAC)基液;使用该PAC基液,在沉降时间5 h、PAC基液与废水体积比1∶120、搅拌转速140 r/min、pH值8、反应温度30℃、聚丙烯酰胺(PAM)投加量20 mg/L条件下处理含锰酸性废水,处理后液中锰质量浓度由325.3 mg/L降至1.5 mg/L,锰去除率达99.5%,净化后液中锰质量浓度达到国家一级排放标准。

F-53B胁迫下污水厌氧处理系统及微生物群落的响应

通过构建厌氧反应体系,评估低浓度(1mg/L)和高浓度(10mg/L)氯化多氟醚磺酸盐(F-53B)胁迫下,厌氧处理系统出水水质、污泥性状和细菌群落的响应特征.结果表明,在F-53B的胁迫下,COD、氮(TN、NH_(4)^(+)-N)和磷(TP、PO_(4)^(3-)-P)在出水中的含量会升高,而污泥相对生物量(MLVSS/MLSS)则出现下降,且F-53B的浓度越高影响越大.高通量测序分析发现,相较于对照组(0mg/L F-53B),仅高浓度F-53B胁迫下细菌群落的多样性(ACE、Chao1和PD指数)出现了显著下降.同时,研究还发现,随着高浓度F-53B暴露时间的延长,厚壁菌门的相对丰度逐渐增大,而变形菌门、拟杆菌门和硝化螺旋菌门的相对丰度逐渐降低.此外,基于FAPROTAX功能预测分析发现,F-53B胁迫下微生物表现出更低的氮(N)代谢潜力和更高的化能异养和发酵能力.冗余分析(RDA)表明,厚壁菌门主要受F-53B的正向影响,并与TN和NH_(4)^(+)-N呈正相关;而变形菌门受F-53B的负向影响,并与COD、TP和PO_(4)^(3-)-P呈正相关.揭示了新型氟化物—F-53B对污水厌氧处理系统的胁迫机制.

零价铁活化过氧乙酸降解水中双酚A的效果与机制

双酚A(BPA)是含酚工业废水中代表性污染物,采用零价铁(ZVI)活化过氧乙酸(PAA)去除水中BPA,探究了ZVI和PAA投量、pH以及工业废水中典型共存阴离子对PAA活化和BPA降解的影响,并通过探究反应活性物种和活性位点解析了ZVI活化PAA的反应机制。在投加50 mg/L ZVI,1.00 mmol/L PAA和初始pH为3.4的最优工艺条件下,ZVI/PAA体系反应30 min可去除水中99.24%的BPA;HCO_(3)^(-)和SO_(4)^(2-)对BPA降解具有抑制作用,Cl^(-)(0~20.0 mmol/L)则加速BPA降解。反应中ZVI及其表面氧化层分别释放溶解性Fe(Ⅱ)和Fe(Ⅲ),溶出的Fe(Ⅱ)活化PAA贡献26.46%的BPA降解,非均相ZVI活化PAA对BPA降解起主要作用;淬灭实验表明,ZVI/PAA体系存在CH_(3)C(O)OO·、CH_(3)C(O)O·、·OH和FeⅣO^(2+),其中CH_(3)C(O)OO·和FeⅣO^(2+)是降解BPA的主要活性物种。本研究可为工业废水中双酚A的有效去除提供理论和数据支撑。

贵州省废弃闭坑煤矿酸性废水治理新方法探讨

煤矿开采过程中和闭坑后产生的大量酸性废水未得到及时有效的处理,通过矿硐井口源源不断地向外排放,对周边生态环境造成了严重破坏。为有效处理废弃闭坑煤矿酸性废水排放问题,降低或消除其带来的环境破坏,在分析国内外有关煤矿酸性废水治理现行技术和方法基础上,围绕贵州省废弃闭坑煤矿酸性废水排放的现状及特点,根据煤矿酸性废水中有毒有害物质的成分和含量,结合有关规范标准对矿山废水污染物排放标准限值的要求,提出了一种治理该类矿山酸性废水的方法:即对闭坑煤矿井口排水采取巷道内设置挡水墙+巷道充填+封闭墙的巷道封闭充填技术。通过实例验证,矿山一井口不再排水,矿山二水质检测指标中pH值由原来的5.26上升至7.93,从酸性变为弱碱性;总铁由34.30 mg/L下降至0.06mg/L,总锰由4.34mg/L下降至0.05mg/L;总悬浮物、化学需氧量(COD_(Cr))和石油类指标变化不明显,基本实现从源头上对废弃闭坑煤矿酸性废水的有效治理。

矿山酸性废水治理的研究及SAPS技术展望

总结论述了矿山酸性废水(AMD)的形成和治理状况,重点论述了被动处理技术中的SAPS技术及其处理效果,认为SAPS技术是一种对酸性废水治理有发展前途的技术。

含铬废水和污泥中铬的处理研究进展

随着“绿色发展”观念的持续推进,传统制革行业因其生产工艺中产生的污染而逐渐受到冲击。制革鞣制过程所产生铬鞣废水及其处理后所产生的污泥,若得不到有效处理和利用,不仅会对环境和人的身体健康产生危害,还会造成铬资源的大量浪费,经济、高效的铬处理与利用技术的开发已迫在眉睫。基于此,分别对制革过程产生的含铬废水及其沉淀过程产生的污泥中铬的处理方法进行了介绍,如循环利用法、电絮凝法、生物沥滤法和超临界水氧化法等,并对含铬废水和污泥中铬的处理回收方法的发展进行了总结和展望,旨在为我国皮革行业的绿色化发展提供一种新的思路。

含氟废水中氟化钙颗粒结晶行为及其可浮性研究

为解决氟资源加工利用过程中的环境污染问题,并提高含氟废水中氟资源的综合利用率,系统研究了含氟酸性废水中形成的氟化钙结晶颗粒的沉降行为和粒度特征,探索了氟化钙结晶颗粒的浮选特性,并结合Visual MINTEQ软件模拟氟化钙化学沉淀形成过程,利用XRD表征结晶颗粒的物相组成,采用Zeta电位测试分析Na OL与氟化钙颗粒的作用机理。研究结果表明:用氯化钙处理含氟酸性废水时,在强酸条件下,无法形成氟化钙结晶颗粒;在p H>5时,能获得稳定的氟化钙结晶沉淀产物,且废水中F^(-)浓度越高,结晶颗粒数量越多,粒度越大,所获得氟化钙结晶纯度高,几乎不含其他杂质;油酸钠在p H为5~9时,能够吸附在氟化钙结晶颗粒表面,使其具备良好的可浮性,且油酸钠用量与废水中F^(-)浓度呈等比例关系,浮选回收效果良好。该研究结果可为处理含氟废水和回收氟化钙资源提供理论参考。

Redox behavior and chemical species of arsenic in acidic aqueous system

Arsenic(As)removal from smelting acidic wastewater is an urgent task.The most common method is oxidation of trivalent As(III)to pentavalent As(V)subsequently precipitated by ferric(Fe(III))salts.Foundations of redox behavior and chemical species are of great importance for understanding As removal.In this work,cyclic voltammetry(CV)and UV?Vis spectroscopy were used for laboratory observation;meanwhile HSC and MINTEQ software were employed for theoretical analyses.It is found that As(III)oxidation,a multiple electron transfer reaction,is diffusion-controlled.The oxidation over-potential is very high(about0.9V)in sulfuric acid solutions(pH1.0).In addition,Fe(III)?As(V)complexes are evidenced by UV?Vis spectra and chemical species analyses in series of Fe(III)?As(V)?H2SO4?H2O solutions.Therefore,the Fe(III)and As(V)species distribution against pH values are determined and a newφ?pH diagram with inclusion of Fe?As complexes is consequently compiled based on thermodynamic data predicted by other researchers.

焦化尾水资源化回用集成工艺中试

为实现焦化尾水的资源化回用,开发了以预处理、压力-电驱动膜组合及双极膜电渗析技术为核心的集成工艺,并进行了中试研究。集成工艺中,化学软化和臭氧-双氧水复合氧化工艺用于去除原水中的硬度和反渗透浓水中的难降解有机物,纳滤工艺完成了一价离子与高价离子的分离,电渗析和双极膜电渗析工艺实现了焦化尾水的近零排放和酸碱资源再生。化学软化工艺对原水的硬度去除率可达64.2%;臭氧-双氧水复合氧化工艺对反渗透浓水的COD去除率可达35.0%;纳滤工艺的脱盐率可达30.2%,对氯离子、硫酸根、硬度和TOC去除率分别可达-6.8%、97.3%、78.4%和87.4%;双极膜电渗析工艺可得浓度均为2 mol/L以上的酸和碱,能耗为4.0 kW·h/kg。该集成工艺的水回用率大于90%,酸碱可短程循环利用。

基于单宁酸-铁(Ⅲ)改性正渗透膜制备及抗污染性能

采用表面涂覆的方法对三醋酸纤维素(CTA)正渗透膜的活性层进行改性,首先利用单宁酸(TA)与铁离子(Fe^(3+))在膜表面以自组装的形式构建金属-多酚前体层,在此基础上进一步涂覆单宁酸/二乙烯三胺(TA/DETA)亲水功能层,最后借助TA的还原性在膜表面原位形成Ag/聚乙烯吡咯烷酮(PVP)抗菌功能层,制备了TA/Fe^(3+)-TA/DETA-Ag/PVP改性膜。利用错流式正渗透装置探究动态污染实验中膜通量的变化情况,通过扫描电子显微镜(SEM)和红外光谱(FTIR)分析膜污染前后表面形貌和组成,使用激光共聚焦显微镜(CLSM)对膜表面污染物微观分布进行表征,并对比CTA原膜和改性膜的清洗效能。结果表明:TA/Fe^(3+)-TA/DETA-Ag/PVP改性膜的水接触角由78.79°下降至33.05°,亲水性显著提升。在15天的动态污染实验结束后,CTA膜和TA/Fe^(3+)-TA/DETA-Ag/PVP改性膜的通量分别衰减为各自初始通量的52.14%和72.81%,且与CTA原膜相比,TA/Fe^(3+)-TA/DETA-Ag/PVP改性膜表面的活细菌数量和有机污染物量大幅减少。经过水力清洗和渗透反洗后,TA/Fe^(3+)-TA/DETA-Ag/PVP改性膜的通量恢复率可达80.37%,远高于CTA原膜的49.88%,具有较强的抗污染性。

基于SRB的升流式厌氧反应器处理AMD的探究

在矿山开采过程中产生的酸性矿山废水(AMD)具有pH低、重金属离子和硫酸根离子浓度大等特点,处理不当会导致严重的环境污染问题。以硫酸盐还原菌(SRB)为主的生物法是一种极具应用前景的技术。通过填充活性炭的升流式厌氧反应器,对120 d的连续流实验中SO_(4)^(2-)和重金属的还原效果进行了研究。结果表明,该升流式厌氧反应器对模拟AMD中的SO_(4)^(2-)和重金属具有很好的处理效果,在SO_(4)^(2-)、Cu^(2+)、Mn^(2+)、Fe^(2+)、Cd^(2+)进水浓度分别为1000、3、6、30、2 mg/L,去除率可达85%、92%、86%、80%、100%。运行过程中该反应器的ORP始终低于-420 mV,为SRB提供良好的厌氧环境。同时,该SRB菌群能适应进水pH为5.5的酸性废水,可顺利完成硫酸盐还原及重金属沉淀。微生物群落的变化表明,重金属离子浓度的增加显著改变了反应器内微生物的群落结构,但该SRB菌群具有较好的重金属耐受性,脱硫生孢菌属(Desulfurispora)、脱硫弧菌属(Desulfovibrio)和脱硫弯曲孢菌属(Desulfosporosinus)在重金属离子浓度增加的条件下,丰度都有明显增加。SRB对SO_(4)^(2-)和重金属的还原效果为处理AMD废水提供了理论依据和方法借鉴。