改性纳米炭黑对生活垃圾堆肥重金属不同形态的影响

Effects of Modified Nanoparticle Carbon Black on Heavy Metal Forms in Municipal Solid Waste Compost

垃圾堆肥富含N、P、K、有机质等植物所需的营养物质,但同时也含有大量的重金属,需要钝化处理。纳米炭黑具有吸附性,在钝化修复重金属方面具有应用前景;但纳米炭黑是疏水性的非极性吸附剂,为了提高其钝化能力,需进行改性处理。本实验采用2种氧化性无机酸、酸性高锰酸钾、3种无机碱对纳米炭黑进行了改性处理,并按5%的比例添加到垃圾堆肥产品中,研究了改性纳米炭黑对堆肥重金属不同形态含量的影响。结果表明,改性纳米炭黑均可显著降低重金属的可交换态及碳酸盐结合态比例,其中,KMnO4改性纳米炭黑对Cr、Pb最为有效,分别比对照降低了71.13%和73.48%;而HNO3改性纳米炭黑使Cu和Zn的可交换态及碳酸盐结合态比例分别比对照降低了67.67%和74.33%。另外,3种氧化改性纳米炭黑降低了Fe/Mn氧化物结合态重金属含量,增加有机物及硫化物结合态含量,而3种碱改性纳米炭黑的结果正好相反。改性纳米炭黑明显降低了堆肥结合态重金属的总含量,增加了残渣态重金属的含量,使重金属从植物易吸收态向不易吸收态转化。

Composting has been proved to be an effective way to reduce the amount of municipal solid wastes （MSW） and to recycle MSW. Composted MSW contains abundant nutrients such as organic matter, N, P and K. It is not only a fertilizer but also a soil conditioner. How- ever, toxic metals in MSW composts have limited its agricultural use. Nanoparticle carbon black（nano-CB） has showed a potential to reme- diate soil heavy metal pollution. Nano-CB, a nonpolar and hydrophobic sorbent, needs to be modified to enhance its adsorption of heavy metals. In this study, nano-GB modified by KMnO4, H2SO4, HNO3, NaOH, Na2CO3 and NH3 H2O was added into MSW compost at a rate of 5% and the composts were then incubated for 45 d. Heavy metal forms in the MSW composts were extracted with the BCR sequential ex- traction procedures. The modified nano-CB significantly reduced exchangeable and carbonate fractions of heavy metals. Compared with the control, KMnO4 modified nano-CB decreased exchangeable and carbonate fractions of Cr and Pb by 71.13% and 73.48%, respectively. HNO3 modified nano-CB respectively reduced exchangeable and carbonate fractions of Cu and Zn by 67.67% and 74.33%. Nano-CB modi- fied by three oxidizing agents lowered Fe-Mn oxide fractions but increased organic/sulphide fractions, while nano-CB modified with three alkali agents yielded contrary results. Adding modified nano-CB to composts enhances transformation of heavy metals from loosely- into tightly- absorbed forms and reduces heavy metal bioavailability.