黏土矿物对镉污染土壤的原位钝化修复

分别以黏土矿物海泡石、凹凸棒土和硅藻土作为钝化材料,对重金属镉污染的土壤进行原位钝化修复,通过室内土壤培养实验考察了3种矿物在不同添加剂量下对土壤pH值和重金属镉形态变化的影响。结果表明,3种矿物均不同程度提高了土壤pH值,大大减少了可直接被生物利用的弱酸提取态镉含量,极大的增加了几乎不被生物利用的残渣态镉含量。这表明,3种矿物的施加均可促进土壤中镉的形态由弱酸提取态向残渣态转变,降低土壤中镉的生物有效性。其中施加3%海泡石处理下的土壤重金属镉由弱酸提取态向残渣态转变的比例最大,表现出较好的修复效果。     

生物土壤结皮的表征分析与吸附去除水体中镉的试验

通过从四个典型南方稻田环境采集灌溉水,土壤和生物结皮。筛选出镉污染程度最轻的生物土壤结皮并对其进行表征分析以及去除水体中镉的性能研究,表明生物土壤结皮为生物组分和土壤矿质元素的复合体,具有大量表面官能团。性能研究表明吸附容量与平衡浓度基本呈线性关系,最大吸附容量为8.481 mg/g;对水溶液中镉的最大去除率为99.79%。对镉吸附最适pH值为7且去除率达87.03%。在含高钙环境下对镉具有选择性吸收特征,同时对于平均分子量数量级低于10~7的络合态镉亦有较好的去除效果。生物结皮对去除水体中的镉具有潜在价值。     

龙葵吸附重金属镉的生物有效性的研究

选取龙葵及种植龙葵的土壤作为研究对象,测定土壤中重金属镉的含量、土壤重金属可交换态镉、碳酸盐结合态镉、铁锰氧化物结合态镉、有机结合态镉、残渣态镉的化学形态含量,同时测定土壤的阳离子交换量、比重、pH等,并分析了土壤中不同化学形态的重金属镉的分布特征,同时分析影响重金属镉形态分布及生物有效性的因素.结果表明,土壤重金属镉...     

不同钝化剂对轻污染农田镉和铅含量的影响

以中山市坦洲镇轻污染农田为研究对象,开展了铁基生物炭土壤调理剂、某研究所自主研发的土壤改良剂对土壤镉、铅污染修复效果的研究。结果表明两种钝化剂均能显著降低蔬菜中的镉含量;对铅的效果一般;土壤改良剂的修复效果优于铁基生物炭。对于同水平的轻污染农田,铁基生物炭调理剂最佳施用量为基准用量,即1亩50 kg,土壤改良剂的最佳施用量为基准用量的1.5倍用量,即1亩150 kg。施用后,土壤pH基本都有一定的下降。总镉、总汞、总铅、有效态镉、有效态铅基本均呈明显的减少。总铬呈现增减的略微波动。总砷略微增加。有机质明显增加。     

几种调节剂对农田土壤镉污染的原位修复研究

土壤污染日趋严重,我国土壤总超标率达16.1%,其中重金属镉超标率最高,可达7.0%。据统计,我国镉污染农田面积约为28万公顷,年产镉超标农产品150万余吨,治理农田镉污染问题刻不容缓。本文选取贝壳粉、氢氧化钙、氧化镁、钙镁磷肥等钝化材料,分别针对低镉及高镉污染的农田土壤进行实验,探究几种调节剂对镉污染农田土壤中pH值、土壤有效态镉含量及降低率的调控作用,从而对后期土壤修复工程做指导。     

石灰、腐植酸单施及复配对污染土壤铅镉生物有效性的影响

正通过盆栽试验研究在铅(Pb)、镉(Cd)污染土壤中单一及复合添加石灰(w=0.2%)和腐植酸(w=1%、2%和5%)对土壤理化性质、土壤有效态Pb和Cd含量、黑麦草生长及黑麦草吸收Pb和Cd的影响,探讨石灰和腐植酸对土壤Pb、Cd生物有效性的调控效率。结果表明:单施石灰和石灰配施腐植酸处理均能提高土壤pH,显著降低土壤中有效态Pb、Cd含量,     

生物炭对矿区土壤重金属有效性及形态的影响

为探索生物炭作为改良剂修复矿区重金属污染土壤的可行性,以玉米秸秆为原料在450℃制备生物炭,采用扫描电镜、能谱分析以及傅里叶变换红外光谱等分析与测试手段对其进行表征。采用室内连续培养的方法,研究在不同培养时间条件下,添加不同施用量（0、1%、3%和5%）的生物炭后,对矿区土壤pH,阳离子交换量（CEC）,土壤重金属Cu、Zn、Pb和Mn有效性以及重金属不同形态变化的影响。结果表明：生物炭能够提高土壤的pH和CEC,且都随着添加量的增加而增加。56d土壤培养后,与对照相比,1%、3%和5%添加水平下pH分别增加了1.14个、1.42个和1.67个单位,土壤CEC分别增加了2.02cmol/kg、3.60cmol/kg和5.39cmol/kg。添加不同含量生物炭后,土壤中有效态重金属均呈现不同程度的降低,而且生物炭添加量越大,降幅也越大。在5%添加水平下,生物炭分别使Cu、Zn、Pb和Mn有效态下降了49.2%、46.2%、72.5%和26.3%。重金属有效态含量与土壤pH、CEC均呈显著负相关关系。添加生物炭后,土壤中重金属的形态发生了变化,由易迁移的弱酸提取态向更加稳定的残渣态转化,且生物炭添加量越大,钝化效果越显著。综上所述,玉米秸秆生物炭的添加提高了矿区重金属复合污染土壤的pH和CEC,促进了重金属复合污染土壤中Cu、Zn、Pb和Mn的弱酸提取态向化学性质稳定的残渣态转化,降低了土壤重金属的有效性,实现了对重金属复合污染土壤的修复。     

生物钝化修复镉污染土壤研究进展

回顾了我国含镉土壤的场地修复。综述了利用生物钝化技术修复镉污染土壤的研究现状,重点探讨了微生物的代谢产物与镉产生硫化物或磷酸盐沉淀的微生物沉淀作用、微生物的细胞壁和其分泌的胞外聚合物直接吸附镉的微生物吸附作用以及镉离子透过微生物的细胞膜而被固定在细胞内的微生物摄取作用等生物钝化机理,并对有机钝化过程和无机钝化过程进行了介绍和评价。分析了镉在土壤中的离子交换态、碳酸盐结合态、铁锰氧化物结合态、有机结合态和残渣态等赋存形态以及土壤中pH值、氧化还原电位、有机质、共存重金属和微生物等因素对镉的生物可利用度的影响。最后阐述了生物钝化技术的优点以及该技术不能将重金属从土壤中永久去除的问题,指出生物钝化技术与其他修复方法相结合是其未来的发展方向。     

熟石灰-矿渣联合修复重金属污染土强度及淋滤特性研究

固化/稳定化修复技术已经成为治理重金属污染土的一种有效且经济的技术.以沈阳矿渣堆场污染土为研究对象,使用熟石灰和高炉矿渣作为混合固化剂,进行固化/稳定化联合修复重金属铬和镉污染土试验研究,测定不同固化剂掺量、不同含水量、不同养护龄期条件下,联合固化污染土的无侧限抗压强度、浸出特性及酸中和能力.结果表明,熟石灰-高炉矿渣联合修复镉和铬污染土壤具有有效性,力学性能主要由固化剂掺量和水含量控制,而重金属铬和镉的浸出主要受pH和固化剂掺量的影响;熟石灰与高炉矿渣质量比1∶4作为混合固化剂掺量20％、含水量为最佳含水率22％时,满足填埋场的废物接受标准和相关环境质量标准要求.     

某锌冶炼厂下游农田土壤镉污染成因分析

为查明某锌冶炼厂下游农田土壤镉污染现状及污染成因。于2021年3月在某锌冶炼厂下游采集了190个表层土壤、50个深层土壤和49个地表水样品,并对样品进行了pH、Cd含量的测定。采用富集因子法、重金属单因子评价法对土壤中Cd进行了评价。结果表明：研究区表层土壤pH值范围为4.52～6.45,土壤总体呈强酸性,镉含量范围为0.204～27.984mg/kg,地表水镉的含量范围为0.011～178.529μg/L;重金属分因子评价结果表明,研究区农田土壤镉环境质量类别以安全利用为主,面积1150.1亩,分布在研究区的西部、北部,在东南部也有较大面积分布;镉严格管控耕地面积600.2亩,分布在研究区南部以及沿中部河流两岸,在西南角有小面积分布;优先保护区面积很小,仅有50.7亩,在研究区北部零星分布。镉污染来源与迁移途径分析结果表明,研究区内农田土壤镉污染的主要来源为炼锌厂地块,越靠近该污染源,土壤和地表水中的镉含量就越高。从镉污染迁移途径分析可知,研究区沿河两岸农田土壤的污染类型为水型污染,炼锌厂周边为气型和水型的混合污染。     

Adsorption of zinc, cadmium and mercury ions from aqueous solutions on an activated carbon cloth

The adsorption of zinc, cadmium and mercury ions from aqueous solutions on an activated carbon cloth was studied as a function of their concentrations and solution pH. For that purpose, pertinent adsorption isotherm data was collected at different pH values. The amount of adsorbed zinc and cadmium ions increases while the amount of adsorbed mercury remains constant with an increase in the equilibrium pH of the solution. The adsorption mechanisms of metal ions on activated carbon cloth are discussed. Under the conditions investigated, these primarily involve adsorption of monovalent cations (Zn and Cd) or precipitation of metal hydroxides (Cd and Hg) on the activated carbon cloth tested.     

Influence of phosphate on cadmium adsorption by soils

In batch equilibrium experiments, it was found that orthophosphate increased Cd adsorption and decreased its desorption by three representative soils. Ion activity products in the equilibrium solution indicated that cadmium activity was under saturated with respect to Cd₃(PO₄) (s) on the Red earth(Typic Hapludult) and the Yellow-brown earth(Typic Hapludalf). With the calcareous Yellow fluvo-aquic soil(Typic Haplaquent), phosphate enhanced Cd adsorption at lower Cd concentration but it decreased the adsorption at high Cd level. Ion activity products and solubility diagrams suggested that at high Cd level Cd₃(PO₄)₂ had formed and the activity of Cd in solution was controlled by this precipitate. This implies that the formation of Cd₃(PO₄)₂ (s) is unable to decrease Cd activity so long as soil adsorption sites are unsaturated by Cd. It is suggested from these results that one could not expect decreasing soil Cd availability by phosphate fertilization unless a simultaneous rise in soil pH also occurs.     

内秦淮河逸仙桥处沉积物中镉吸附与释放及形态转化研究

通过研究不同环境条件对镉在内秦淮河逸仙桥处沉积物中的吸附与释放及形态转化规律的影响,发现吸附量和释放量都随温度升高而增大;吸附量随pH值增大而增大、随盐度增大而减小;pH值改变对沉积物中镉形态的影响较小。盐度增大,镉的生物有效性降低。镉释放量随pH值增大而减少、随盐度增大而增大。在不同环境条件下,沉积物中镉达最大释放量时释放的形态不同,pH值为5时,释放镉以碳酸盐结合态为主,由20.67%降至2.1%;盐度为10%时,释放镉以有机结合态为主,由15.24%降至6.32%;温度为30℃时,以可交换态为主,由16.48%减少至1.6%。     

Synergistic effects of phosphoric acid modified hydrochar and coal gangue-based zeolite on bioavailability and accumulation of cadmium and lead in contaminated soil

In this paper, a novel compound was developed by mixing H₃PO₄-modified cauliflower leaves hydrochar (CLH) and coal gangue-based Na-X zeolite (ZL). An alkaline soil contaminated with cadmium (Cd) and lead (Pb) was amended through the individual and synergistic application of CLH and ZL (1%CLH, 2%CLH, 1%ZL, 2%ZL and 1%CLH + 1%ZL), and Chinese cabbage was grown on it. Individual application of CLH was superior to ZL on decreasing the pH of alkaline soil and increasing soil available phosphorus (Olsen-P) and soil organic matter (SOM). In contrast, their combined application significantly improved the soil cation exchange capacity (CEC). Besides, the 1%CLH + 1%ZL was the most efficient treatment in decreasing diethylenetriamine pentaacetate (DTPA)-extractable Cd/Pb and concentrations of these two metals in cabbage root and shoot. Their synergistic application could better increase Cd and Pb immobilization and cabbage yield than their alone application. Furthermore, the immobilization of Pb for all treatments was higher than that of Cd. The synergistic immobilization mechanism of CLH and ZL reflected that the CLH precipitated and complexed with these two metals, which may block the pores of hydrochar or wrap on the surface of hydrochar. So the continuous adsorption and complexation were prevented. Nevertheless, ZL could probably alleviate this obstacle. This finding provides helpful information about using CLH combined with ZL as a soil stabilizer to immobilize heavy metals in contaminated alkaline soil.     

不同热解温度生物炭对溶液中镉的吸附性能研究

以玉米秸秆、枫杨树枝、花生壳为生物质材料,分别在450、550、650℃下,对3种生物质材料进行厌氧热解制备了9种生物炭,对溶液中的Cd2+进行吸附试验,研究了pH、生物炭投加量、吸附时间和Cd2+初始质量浓度对Cd2+吸附效果的影响。结果表明,吸附过程与Langmuir、Freundlich和准一级动力学方程拟合的相关性较好。pH对吸附的影响较大,吸附率与生物炭的投加量呈正比,650℃制备的3种生物炭的吸附能力更强,花生壳生物炭对溶液中的Cd2+具有更好的吸附能力。     

Effect of formate and methanol on photoreduction/removal of toxic cadmium ions using TiO2 semiconductor as photocatalyst

Photoreduction/removal of cadmium was studied at pH 7 using TiO₂ Degussa as photocatalyst, and either formate or methanol as hole scavengers. In the absence of organic additives, approximately 60% of cadmium was found to be removed from the solution by adsorption. Addition of formate resulted in the photoreduction of cadmium to its metallic form. No cadmium reduction was observed when methanol was added as the hole scavenger. Zeta potential measurements of the catalyst suspensions and studies on the extent of organic additive adsorption and mineralisation were used to prove the photoreduction process. It was found that the adsorption of both cadmium and the organic hole scavenger is crucial for the photoreduction of cadmium. It is postulated that to be an effective hole scavenger the organic additive needs to be easily photooxidised under an anoxic environment. In addition, the presence of formate radicals could be responsible for the Cd photoreduction.     

Electrokinetic remediation of lead‐, zinc‐ and cadmium‐contaminated soil

Electrokinetic remediation of lead‐, zinc‐ and cadmium‐contaminated sand and clayey soils has been investigated under laboratory‐scale conditions. Soil extracts of heavy metals (by 1 M HCl solution) were analysed by optical emission spectrometry. The efficiency of electrochemical remediation was partially dependent on the pH of the soil media. With pH increase, the migration of heavy metal ions toward the cathode was limited. When acetic acid was added to the sandy soil, almost complete remediation was achieved. A clay layer inserted in the cathode area did enhance the remediation rate. The most effective clean‐up was achieved for zinc and cadmium, with less effective clean‐up being achieved for lead. The effectiveness of the electrokinetic remediation of heavy metal‐contaminated clayey soil was low. The appropriate acidity was not achieved using acetic acid because of the high buffering capacity of clay, and metal ion migration was impeded by its sorption onto some clay components. The conclusion was made that clays could be used as immobilizing media for heavy metal ions by electrokinetic remediation of various soils. © 2001 Society of Chemical Industry     

Adsorption of cadmium from aqueous solution by phosphogypsum

In the present study, the adsorption of cadmium on phosphogypsum, a waste material from the manufacture of phosphoric acid by wet process, was studied. Before batch adsorption study, phosphogypsum was pre-conditioned by milk of lime. Effect of initial pH on cadmium adsorption was investigated. It was found that cadmium adsorption was dependent on solution pH and maximum cadmium removal was observed in the pH range of 9.5 and 11.5. The Langmuir and Freundlich theories were used to describe the cadmium adsorption process, and the Freundlich isotherm showed the best fit to the process. Maximum adsorption capacity of lime-preconditioned phosphogypsum was found to be 131.58 mg/g.     

柠檬酸工业废水强化镉污染土壤的电化学法修复

通过批量解吸附实验和电化学修复实验,研究利用柠檬酸工业废水作为电化学修复的增效剂从高缓冲容量的天然土壤中去除镉的可行性。批量实验结果表明,当加入柠檬酸工业废水时,85%以上的镉能在土壤pH≤5.0的条件下从土壤中溶解到溶液中;在pH5.0～8.0范围内镉的解吸附率比用去离子水增加20%～45%。电化学修复实验结果表明,与相同pH值的HNO₃相比,该废水作为电极溶液可使镉在土壤中发生明显迁移;在距离阳极0～4 cm及8～10 cm处土壤镉含量由282 mg·kg^-1降低至167～200 mg·kg^-1,而在距阳极4～8 cm处土壤镉含量升高至约400 mg·kg^-1。经过514 h的电化学修复,约84.7%的镉可以从土壤中去除,其中约94.6%从土壤中去除的镉富集在阴极溶液中。可见柠檬酸工业废水是一种非常有前景的重金属污染土壤电化学修复增效剂。     

海泡石处理含镉废水技术研究

对海泡石去除废水中镉离子的方法进行了实验探讨。结果表明．海泡石对去除水中的镉离子具有较好的作用,可以将含Cd^2 10mg/L的水净化至0．1mg／L以下,去除率达到了99％以上,海泡石与含(Cd^2 溶液的作用时间、海泡石用量、水中(Cd^2 浓度以及酸度等因素都会影响(Cd^2 的去除效果。海泡石去除(Cd^2 的机理是基于吸附和离子交换共同作用。其吸附交换容量为Y(mg／g)=X／(0．052X 0．047)。