温控电动联合淋洗法去除污染淤泥质黏土中铬的试验研究

自行设计了温控电动联合淋洗试验装置,开展了铬污染淤泥质黏土室内土柱试验,分析了电流、电解质溶液pH的变化以及淋洗液种类、外加电压、温度对铬去除效果的影响。结果表明:电动联合淋洗法可以有效去除土体中的重金属铬,当电压较小为15 V,淋洗液为十二烷基苯磺酸钠(SDS)和草酸(OA)时,Cr(Ⅵ)的去除率分别高达95.86%和95.91%,Cr(总)的去除率分别为81.31%和78.08%。升高温度有助于草酸与铬的络合作用及铬的迁移,当温度升高至45℃时,Cr(Ⅵ)与Cr(总)的去除率可高达99.65%与82.50%;而当淋洗液为SDS时,升高温度使Cr(总)的去除率降低了10.99%。电压提高到55V对铬迁移的促进作用有限,淋洗剂为SDS和草酸时,Cr(VI)的去除率分别提高2.58%和3.05%,Cr(总)的去除率分别提高9.29%和3.78%,从节能角度考虑可采用较低的电压。电动联合淋洗法可有效去除污染土中水溶态及弱酸提取态的铬,降低污染土的毒性,并使土粒之间的孔隙变小,土粒结构更为紧密。     

电动法修复镉污染黏性土的试验研究

使用自行设计电动修复装置，针对镉污染黏性土开展了室内土柱试验，分析了土柱中镉的去除效果、修复前后污染土的微观结构变化和镉的形态特征，探究了土壤中镉的去除机制。结果表明：镉初始浓度较小时，增大电压可以显著提高镉的去除率，电压的增大可加快土中不稳定形态镉的迁移。当镉初始浓度较大时，残余在土柱中的镉含量呈现出从阳极侧到阴极侧逐渐增大的现象。经过电动修复后，土颗粒从球形呈现的黏聚体结构变为了光滑、松散的结构。电压为40V时，约95%的弱酸提取态及可还原态镉从土壤中去除，修复后土柱中的残渣态等稳定形态的镉约为总镉的60%，有效降低了镉污染土的毒性。     

高岭土中铅污染物的电动迁移及去除

以人工配制的铅污染高岭土为研究对象,引入新型电动土工合成材料电极,研究铅污染土的电动修复机理。采用两种不同的电动修复手段,通过分析电动修复过程中的电流、土体pH以及铅元素的存在形态,研究不同添加剂对铅污染土去除效率的影响及两种修复手段的差异性。结果表明:电动修复换水试验电流后期存在明显下降阶段,而循环试验电流后期没有下降,而是小幅波动;针对铅污染物修复而言,醋酸类添加剂比柠檬酸类添加剂更有利于铅的去除;柠檬酸与铅离子易生成难电离物质不利于铅的迁移,乙二胺四乙酸二钠能与绝大多数铅离子络合形成络合离子;通过蠕动泵循环阴、阳极电解液可以较好地控制电解水产生的氢离子和氢氧根,避免其对土体pH及重金属形态产生明显影响;修复试验中离子扩散和电解液循环引起的冲刷作用迁移出的重金属较少,占比小于10%,进一步说明电动法去除土体重金属污染物的有效性。     

钢渣处理含铬废水的机理研究

以钢渣颗粒为吸附剂,处理水中Cr（Ⅵ）,采用间歇振荡法,结合等温吸附方程及形态分析试验,探讨了钢渣处理Cr（Ⅵ）的去除机理．结果表明,钢渣吸附Cr（Ⅵ）是单层吸附,符合Langmuir方程;钢渣吸附Cr（Ⅵ）的机理主要表现为：先将Cr（Ⅵ）还原成Cr（Ⅲ）,一部分Cr（Ⅲ）被钢渣直接吸附,另一部分生成沉淀．另外,还有一部分Cr（Ⅵ）及还原后的Cr（Ⅲ）通过化学键的作用与铁锰氧化物结合,被包裹在钢渣内部．     

南水北调中线工程京石段干渠底泥吸附铬研究

近些年水质重金属污染事件频发,南水北调中线工程京石段干渠沿程交叉建筑物较多,对突发意外事故可能产生的水质重金属铬迁移转化规律进行了实验室模拟研究.结果表明,在模拟水流振荡过程中,Cr（Ⅲ）、Cr （VI）之间难以相互转化.酸性条件下底泥对Cr（Ⅲ）的吸附去除效果较好,在pH=5时,底泥对Cr（Ⅲ）的吸附效率最高,为97％;且吸附速度很快,10 min吸附率可达97％左右.Cr（Ⅲ）浓度为1～20 mg/L时,底泥对Cr（Ⅲ）的吸附去除率随铬浓度升高而略有下降,但均在94％以上,底泥对Cr（Ⅲ）的最大吸附量为0.952 mg/g.底泥吸附去除Cr （VI）的效率较低,不同pH、振荡时间条件下,底泥对Cr（VI）的最大去除率为12.50％.不同有机物浓度、吸附时间条件下,底泥对Cr（VI）的最大去除率为20.96％.     

不同含水介质对污染河流中六价铬去除的对比模拟实验研究

室内试验选用3种天然砂土作为渗透介质,以生活污水模拟污染河流,发现铬在粗砂中第13天产生穿透,以后去除率为81%~99%,2种中砂的去除率始终大于92%和96%,铬很难进入地下水;还原和沉淀反应是Cr(Ⅵ)去除的主要机理;由于长期污染河流下部渗透介质始终处于厌氧环境,其中富含还原性物质,Cr(Ⅵ)可以通过沉淀反应大部分得以去除,所以污染的河流不是地下水铬污染的来源。     

钢渣对水溶液中铬的吸附及其动力学研究

以钢渣为吸附剂去除溶液中的铬,考察了pH、钢渣投量及粒径、转速等因素对钢渣吸附效果的影响,并结合吸附动力学和扩散模型及钢渣的矿物组成变化探讨了钢渣对Cr(Ⅲ)的吸附去除机理.结果表明,钢渣对Cr(Ⅲ)具有明显的吸附去除效果,且不受溶液pH值的影响;当体系中存在还原剂Fe(Ⅱ)时,Cr(Ⅵ)可被还原为Cr(Ⅲ)而被钢渣吸附去除;在转速为180 r/min的条件下,钢渣对Cr(Ⅲ)的吸附过程遵循Lagergren一级吸附速率方程及Weber-Morris颗粒内扩散模型,此时钢渣内扩散是吸附过程的主要控制步骤.且Cr(Ⅲ)的初始浓度越高则吸附速率越低;X射线荧光(XRF)和X射线衍射(XRD)分析结果表明,铬在钢渣上的吸附去除主要是通过生成铬氧化物以及与钢渣中的Ca、Fe等元素生成难溶化合物来实现的.     

国标碱式消解法测定含铬土壤的适用性研究

国标碱式消解法(《危险废物鉴别标准》(GB 5085.3—2007))是用于从土壤、淤泥、沉积物等固体废弃物中提取可溶性、吸附和沉淀形式的铬化合物的方法,常用于检测修复后的含铬土壤是否达标.针对化学还原法修复的含铬土壤,怀疑使用国标碱式消解法提取土壤中Cr(Ⅵ)时,导致Cr(Ⅵ)的含量较土壤中实际含量偏低.为探究国标碱式消解法浸提过程中土壤中残留的还原剂对Cr(Ⅵ)的影响,试验用XANES、国标碱式消解法配合二苯碳酰二肼分光光度法检测化学还原法修复土壤中Cr(Ⅵ)浓度变化情况,以XANES检测结果为基准,通过模拟化学还原剂对土壤中Cr(Ⅵ)的还原情况,进一步对碱提取法的适用性进行分析.研究结果表明:Fe(Ⅱ)与Cr(Ⅵ)可共存于亚铁修复后的土壤;土壤中残留Fe(Ⅱ)时,使用国标碱式消解法提取后测得土壤中Cr(Ⅵ)含量偏低,不适合用作化学还原法修复后土壤的Cr(Ⅵ)浸提方法;堆放一段时间后,使用国标碱式消解法浸提后测得的土壤Cr(Ⅵ)含量出现回升,回升是由于土壤中亚铁还原剂的衰减导致消解过程中被还原的Cr(Ⅵ)减少,并非是由于土壤中Cr(Ⅲ)被氧化为Cr(Ⅵ).     

钢铁冷轧线含铬废水处理及同步资源化利用

针对某钢铁厂冷轧机组排放的含铬废水中Cr（Ⅵ）浓度达标但总铬不能稳定达标、铬泥作为危废出厂等问题，采用纤维吸附技术从源头对Cr（Ⅵ）进行回收，确保出水水质达标，并通过基于离子交换技术的转化系统实现Cr（Ⅵ）的资源化利用。通过试验确定吸附系统的最优吸附周期与转化系统的最适pH值。系统优化后，出水Cr（Ⅵ）及总铬浓度分别保持在0.048、0.1 mg/L以下，满足《钢铁工业水污染物排放标准》（GB 13456—2012）；与原工艺相比，无需再外加药剂调节pH值，极大地节省了处理成本；铬泥产量减少90%以上；产生的重铬酸液可实现资源化利用，据统计产生的综合经济效益可达520.6万元/a。     

新型絮凝剂APAC处理含Cr(Ⅵ)废水的研究

采用新型絮凝剂APAC处理含Cr(Ⅵ)的模拟废水,考察了各因素对Cr(Ⅵ)及浊度去除效果的影响。结果表明:该絮凝剂对Cr(Ⅵ)有很好的去除能力,对Cr(Ⅵ)的去除率最高可达92.65%;废水的pH越高,对Cr(Ⅵ)的去除率越大;APAC中的凹凸棒组分对Cr(Ⅵ)的去除起主要作用;当APAC的盐基度为80%、投量为32 mg/L、废水的pH值为7~12时,对Cr(Ⅵ)和浊度的去除效果较佳。APAC絮凝剂对Cr(Ⅵ)的良好去除效果为含铬废水的处理提供了一条新思路。     

An electrokinetic/Fe0 permeable reactive barrier system for the treatment of nitrate-contaminated subsurface soils

Effective nitrate removal by Fe⁰ permeable reactive barriers (Fe⁰ PRB) has been recognized as a challenging task because the iron corrosion product foamed on Fe⁰ hinders effective electron transfer from Fe⁰ to surface-bound nitrate. The objectives of this study were (i) to demonstrate the effectiveness of an electrokinetic/Fe⁰ PRB system for remediating nitrate-contaminated low permeability soils using a bench-scale system and (ii) to deepen the understanding of the behavior and fate of nitrate in the system. Bench-scale laboratory experiments were designed to investigate the influence of the Fe⁰ content in the permeable reactive barrier, the pH in the anode well, and the applied voltage on remediation efficiency. The experimental results showed that the major reaction product of nitrate reduction by Fe⁰ was ammonium and that nitrate reduction efficiency was significantly influenced by the variables investigated in this study. Nitrate reduction efficiency was enhanced by either increasing the Fe⁰ content in the Fe⁰ reactive barrier or decreasing the initial anode pH. However, nitrate reduction efficiency was reduced by increasing the applied voltage from 10 V to 40 V due to the insufficient reaction time during nitrate migration through the Fe⁰ PRB. For all experimental conditions, nearly all nitrate nitrogen was recovered in either anode or cathode wells as nitrate or ammonium within 100 h, demonstrating the effectiveness of the system for remediating nitrate-contaminated subsurface soils.     

羟基磷灰石对大肠杆菌吸附铬(Ⅵ)的影响

以实际水体作为实验用水,探究羟基磷灰石(HA)存在下大肠杆菌(E.coli)对六价铬[Cr(Ⅵ)]的捕获吸附特性。结果表明,E.coli对Cr(Ⅵ)的吸附符合假一级动力学,适宜pH值为6,该条件下E.coli对Cr(Ⅵ)的饱和吸附量为30.71 mg/g。纳米尺寸的HA释放和生物效应受浓度影响,当HA暴露浓度为5 mg/L时,正电性HA附着于细菌表面,促进E.coli与Cr(Ⅵ)接触,E.coli对Cr(Ⅵ)的饱和吸附量达到最高值55.98 mg/g。当HA暴露浓度为10~50 mg/L时,过量的HA附着在细菌表面,改变了细胞膜的通透性,因而吸附量略有降低,但依然高于E.coli单独对Cr(Ⅵ)的吸附量。当HA暴露浓度高于100 mg/L时,团聚在一起的HA对Cr(Ⅵ)也产生吸附作用,提高了体系对Cr(Ⅵ)的去除率。总体来说,HA和E.coli共同作用有助于提高对Cr(Ⅵ)的吸附效率。     

羟基磷灰石对大肠杆菌吸附铬(Ⅵ)的影响

以实际水体作为实验用水,探究羟基磷灰石(HA)存在下大肠杆菌(E.coli)对六价铬[Cr(Ⅵ)]的捕获吸附特性。结果表明,E.coli对Cr(Ⅵ)的吸附符合假一级动力学,适宜pH值为6,该条件下E.coli对Cr(Ⅵ)的饱和吸附量为30.71 mg/g。纳米尺寸的HA释放和生物效应受浓度影响,当HA暴露浓度为5 mg/L时,正电性HA附着于细菌表面,促进E.coli与Cr(Ⅵ)接触,E.coli对Cr(Ⅵ)的饱和吸附量达到最高值55.98 mg/g。当HA暴露浓度为10~50 mg/L时,过量的HA附着在细菌表面,改变了细胞膜的通透性,因而吸附量略有降低,但依然高于E.coli单独对Cr(Ⅵ)的吸附量。当HA暴露浓度高于100 mg/L时,团聚在一起的HA对Cr(Ⅵ)也产生吸附作用,提高了体系对Cr(Ⅵ)的去除率。总体来说,HA和E.coli共同作用有助于提高对Cr(Ⅵ)的吸附效率。     

Removal of co-present chromate and arsenate by zero-valent iron in groundwater with humic acid and bicarbonate

The interactions of co-present Cr(VI) and As(V), and the influences of humic acid and bicarbonate in the process of Cr(VI) and As(V) removal by Fe⁰ were investigated in a batch setting using simulated groundwater with 5 mM NaCl, 1 mM Na₂SO₄, and 0.8 mM CaCl₂ as background electrolytes at an initial pH value of 7. Cr(VI) and As(V) were observed to be subject to different impacts induced by co-existing As(V) or Cr(VI), humic acid and bicarbonate, originating from their distinct removal mechanisms by Fe⁰. Cr(VI) removal is a reduction-dominated process, whereas As(V) removal principally involves adsorption onto iron corrosion products. Experimental results showed that Cr(VI) removal was not affected by the presence of As(V) and humic acid. However, As(V) removal appeared to be inhibited by co-present Cr(VI). When the Cr(VI) concentration was 2, 5, and 10 mg/L, in the absence of humic acid and bicarbonate, As(V) removal rate constants were decreased by 27.9%, 49.0%, and 61.2%, respectively, which probably resulted from competition between Cr(VI) and As(V) for adsorption sites of the iron corrosion products. Furthermore, the presence of humic acid significantly varied As(V) removal kinetics by delaying the formation and aggregation of iron hydroxides due to the formation of soluble Fe-humate complexes and stably dispersed fine iron hydroxides colloids. In the presence of bicarbonate, both Cr(VI) and As(V) removal was increased and the inhibitory effect of Cr(VI) on As(V) removal was suppressed, resulting from the buffering effects and the promoted iron corrosion induced by bicarbonate, and the formation of CaCO₃ in solution, which enhanced As(V) adsorption.     

垃圾填埋场衬垫土壤材料对Cr(Ⅵ)的吸附特性研究

通过静态平衡吸附试验对采用颗粒活性炭及酸活化膨润土改良的垃圾填埋场衬垫土壤材料吸附重金属的特性进行了观察。试验结果表明:研究中的所有土壤样本对Cr(Ⅵ)的吸附属于非线性的Langmuir模式。经颗粒活性炭及酸活化膨润土改良的衬垫土壤材料与天然黏土材料相比,对Cr(Ⅵ)的吸附强度有了很大的提高,说明颗粒活性炭和酸活化膨润土可以作为改良衬垫土壤的材料去吸附重金属。所有土壤样本对Cr(Ⅵ)的吸附量均随着温度的升高而增大,随着土壤固体颗粒浓度的增大而减小。Langmuir等温参数(qm,b)随着土壤固体颗粒浓度的增大而呈对数性减小,但随着土壤固体颗粒浓度进一步增大到某一临界值(例如200 g/L),其值基本稳定了,另外等温参数也随着温度的升高呈线性增大的趋势。由试验结果可以得出,采用较低的土壤固体颗粒浓度所确定的吸附参数值不适合模拟实际工程条件,其值将引起对垃圾填埋场衬垫的迟滞因子作出过高估计。因此,为了获得与实际工程条件比较接近的吸附参数值,静态平衡吸附试验必须在一个充分大的固体颗粒浓度条件下进行。     

Influence of anode material on electrochemical oxidation for the treatment of tannery wastewater

The treatment of tannery wastewater by electrochemical oxidation, mediated by an electro-generated species was carried out under galvanostatic conditions in an electrochemical reactor equipped with anodes based on noble metals and metal oxides (Ti/Pt-Ir, Ti/PbO2, Ti/PdO-Co3O4 and Ti/RhO(x)-TiO2). The decrease in time of chemical oxygen demand, nitrogen (TKN and ammonia), Cr and sulphides was monitored. The study showed that the rate of pollutant removal was significantly influenced by the type of anode material and electrochemical parameters. Different mechanisms contributed to the removal of pollutants when the reactor operated under conditions close to the limiting current for chlorine evolution and under much higher current density, with the reactor performing better at a high current/voltage. The kinetic pseudo-first order model applied for the interpretation of the results showed that the Ti/Pt-Ir and Ti/PdO-Co3O4 anodes performed better than the other two electrodes under the majority of tested conditions, with the highest rate of removal obtained for ammonia (kinetic rate constant k=0.75 min(-1)). Electrochemical oxidation can be applied as a post-treatment after the conventional biological process in order to remove the residual ammonia with low energy consumption (0.4 kWh m(-3)).     

Synergistic effect of coupling zero-valent iron with iron oxide-coated sand in columns for chromate and arsenate removal from groundwater: Influences of humic acid and the reactive media configuration

A column study was conducted using a combination of zero-valent iron (Fe⁰) and iron oxide-coated sand (IOCS) for removing Cr(VI) and As(V) from groundwater. The removal efficiency and mechanism of Cr(VI) and As(V), the effects of humic acid (HA), and the various configurations of Fe⁰ and IOCS were investigated. The results showed that the use of an Fe⁰ and IOCS mixture in a completely mixed configuration can achieve the highest removal of both Cr(VI) and As(V), whilst the effects of HA were marginal in using these reactive materials. The solid phase analysis revealed the occurrence of the synergistic effect in these reactive materials as Fe²⁺ can be adsorbed onto the IOCS and transform the iron oxides to magnetite, providing more reactive surface area for Cr(VI) reduction and reducing the passivation on the Fe⁰. As(V) can then be removed by adsorption onto these iron corrosion products. HA can be adsorbed onto the IOCS so that the impacts of the deposition of HA aggregates on the Fe⁰ surface can be reduced, thus enhancing the Fe⁰ corrosion.     

Electro-oxidation of pistachio processing wastewater using Ti/Pt mesh-type anodes in batch system

In this study, the treatment of pistachio processing wastewater (PPW) by electro-oxidation method was investigated. Ti/Pt-plated electrodes were used for the anode material, and stainless steel electrodes were used for cathode material. Experimental studies were carried out in batch mode. Stirring speed, supporting electrolyte species and concentration, initial pH value, current density, temperature and dilution ratio were selected as experimental parameters effecting removal efficiency. In Ti/Pt electrode experimental studies on the optimum conditions, chemical oxygen demand (COD), total organic carbon (TOC) and total phenols (TP) removal efficiencies were obtained, respectively, as 99.98%, 70.74% and 100%, and energy consumption value was obtained as 297.5 kW-h/m³ (12.39 kW-h/kg COD, 51.29 kW-h/kg TOC and 64.68 kW-h/kg TP). As a result of the experimental studies, the PPW can be treated by electro-oxidation. Given the results of removal efficiency and energy consumption values, it was concluded the electro-oxidation using Ti/Pt anode very appropriate treatment of PPW.     

Chromium removal from ion-exchange waste brines with calcium polysulfide

Chromium removal from ion-exchange (IX) brines presents a serious challenge to the water industry. Although chromium removal with calcium polysulfide (CaS₅) from drinking waters has been investigated somewhat, its removal from ion-exchange brines has not been evaluated to date. In this study, a Central Composite Design as well as experimental coagulation tests were performed to investigate the influence of pH, CaS₅/Cr(VI) molar ratio, alkalinity, and ionic strength in the removal of chromium from IX brines. The optimal pH range for the process was found to be pH 8-10.3 and brine alkalinity did not affect coagulation. The efficiency of chromium removal improved only slightly when the ionic strength increased from 0.1 M to 1.5 M; no significant difference was observed for an ionic strength change from 1.5 to 2.1 M. For chromium (VI) concentrations typically found in ion-exchange brines, a CaS₅/Cr(VI) molar ratio varying from 0.6 to 1.4 was needed to obtain a final chromium concentration <5 mg/L. Maximum efficiency for total chromium removal was obtained when oxidation reduction potentials were between −0.1 and 0 (V). Solids concentrations (0.2-1.5 g/L) were found to increase proportionally with CaS₅ dosage. The results of this research are directly applicable to the treatment of residual waste brines containing chromium.