EDTA、皂素及其混剂淋洗去除猪粪中Cu、Zn的研究

Removing Cu and Zn from pig manure via the leaching method with EDTA,saponin,and their mixture

为了解皂素、EDTA用作淋洗剂对畜禽粪便中重金属的去除效果,以某规模化养殖场的猪粪为研究对象,进行振荡提取实验,研究了单一和混合淋洗剂在不同淋洗剂浓度、pH、液固比、反应时间等条件下对猪粪中Cu、Zn的浸出效果,并对处理前后的重金属形态和农用性能进行了分析。结果表明:EDTA和混剂对重金属的去除效果较好,EDTA在浓度为0.1 mol·L-1,液固比25∶1,反应时间30 h,淋洗液原始pH值的条件下,对Cu、Zn去除率分别为75.28%和89.26%;0.05 mol·L-1EDTA和2%皂素组成的混剂在液固比25∶1,反应时间为12 h,淋洗液原始pH时,对Cu、Zn去除率分别为81.44%和91.27%。皂素主要去除离子可交换态和部分碳酸盐结合态,EDTA和混剂可以有效去除离子可交换态、碳酸盐结合态、铁锰氧化物结合态和有机结合态。淋洗后猪粪中有机质、全氮、全钾、全磷的平均含量分别为897.93、20.15、0.64、8.66 g·kg-1。研究表明:EDTA和混剂对猪粪中Cu、Zn的去除效果非常好,可以实现非稳定形态的高效去除,处理后猪粪中Cu和Zn的含量远低于限量标准,毋需后续固化处理,且淋洗后的猪粪仍有很高的营养价值和肥力。

The aim of this study is to explore the feasibility of using EDTA,saponin,and their mixture as eluting agents to remove heavy metals from livestock manure.The pig manure used in the experiment was obtained from a large-scale farm.The effects of EDTA,saponin,and their mixture(E-S mixture)on the removal of Cu and Zn from pig manure under different conditions,such as various concentrations,pH levels,liquid-solid ratios,and reaction time,were studied.The binding forms of heavy metals and the agricultural value of pig manure were analyzed before and after the treatment.Results showed that Cu and Zn could be efficiently leached out from pig manure by both EDTA and the E-S mixture.Under optimum operating conditions,the leaching efficiency of Cu and Zn were 75.28%and 89.26%,respectively,with EDTA and 81.44%and 91.27%,respectively,with the E-S mixture.The extracted Cu and Zn were primarily derived from the exchangeable forms and some carbonate fractions using saponin,and all fractions of heavy metals were removed using EDTA and the E-S mixture excluding the residual fraction.The average contents of organic matter,total nitrogen,total potassium,and total phosphorus in the treated pig manure were 897.93,20.15,0.64,and 8.66 g·kg^-1,respectively.The study indicates that chemical leaching with EDTA and the E-S mixture is highly efficient in the removal of Cu and Zn from pig manure.EDTA and the E-S mixture remove most of the heavy metals in unstable forms.In addition,the treated pig manure retain a high nutrient content and fertility and does not need to be further processed.