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近年来,土壤重金属污染日益严峻,已成为制约中国农业可持续发展的因素之一[1]。虽然土壤修复技术众多,但是随着绿色可持续修复(GSR)运动的兴起,研究者更希望通过绿色方法修复污染土壤,减少潜在的二次污染,以确保过程的可持续性。因此,探索碳排放更低和净环境效益更高的修复技术势在必行[2]。钝化是一种经济有效的土壤修复方法,主要通过物理吸附和化学稳定来固定有毒元素。该技术的关键在于材料的选择。农业废弃物如玉米芯、果壳、秸秆等,直接进行焚烧会产生大量温室气体,如若可以废物利用,不仅能降低处理成本,还能减少碳排放。SHAN et al[3]利用山竹壳制备的生物炭吸附水溶液中的Cr(Ⅵ),去除率可达95.00%以上。SHEN et al[4]通过热解氯化镁预处理玉米芯制备生物炭(MCB),MCB在水溶液中对铅的去除率可达74.00%,应用于土壤后,铅的毒性浸出浓度从10.63 mg/L降低至5.24 mg/L。
山竹是藤本植物科山竹属的一种热带季节性植物,在亚洲国家有大量种植,每公斤山竹大约会产生0.6 kg果壳[5],由于尚未被发现开发利用的价值,造成每年有大量的山竹果壳(Man)被当做农业废物丢弃,对环境造成极大的负担。大量研究表明[3, 6-7],Man经过适当的化学改性,可以显著提高其吸附金属离子的能力,但这些研究大多只关注其在废水处理中的应用,鲜有在土壤中的钝化修复研究。本研究利用KMnO4对Man进行改性,探究了不同条件对改性材料吸附金属离子的影响,并且将其用于重金属污染土壤的钝化修复,为实现土壤的绿色可持续修复(GSR)提供科学参考。
改性山竹壳钝化Cd、Cu、Zn复合污染土壤的研究
Study on passivation of soil polluted by Cd, Cu and Zn by modified mangosteen shell
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摘要: 以天然山竹壳(Man)为原料,采用KMnO4氧化法制备得到改性山竹壳(Mn-Man),通过扫描电镜和红外光谱对Mn-Man进行了物化性质表征,研究了Mn-Man对水溶液中Cd2+、Cu2+、Zn2+的吸附特征,在此基础上将Mn-Man投入重金属复合污染土壤中研究其钝化效果,分析了钝化前后土壤理化性质和重金属稳定性。结果表明:经KMnO4改性后,Mn-Man表面形成粗糙多孔形貌,显著提高了其对金属离子的吸附能力;在pH<5时,静电作用对金属离子的吸附起主导作用,在pH>5时,沉淀作用开始对吸附产生重要影响,Mn-Man对金属离子的吸附顺序为Cu2+>Cd2+>Zn2+;经Mn-Man钝化后,污染土壤pH和肥力明显提高,有效促进重金属从活泼态向不活泼态转化,降低了重金属的TCLP浸出,表明Mn-Man可对重金属污染土壤进行有效修复。Abstract: Modified mangosteen shell (Mn-Man) was produced by using KMnO4 oxidation method with natural mangosteen shell (Man) as the raw materials. The physical and chemical properties of samples were analyzed with FE-SEM and FT-IR. The adsorption characteristics of Mn-Man on Cd2+, Cu2+ and Zn2+ in aqueous solution were studied. On this basis, the passivation effect of Mn-Man was studied in a heavy metal contaminated soil. The changes of soil physical and chemical properties associated with the heavy metal stability before and after passivation were analyzed. The results showed that the surface morphology of Mn-Man was rough and porous after modification by KMnO4. The adsorption capacity of Mn-Man to metal ions was significantly improved. The electrostatic action dominated the adsorption of metal ions with pH<5. The precipitation had an important effect on the adsorption with pH>5. The adsorption sequence of Mn-Man on metal ions was Cu2+>Cd2+>Zn2+. After Mn-Man passivation, pH and fertility of contaminated soil were significantly increased, which effectively promoted the transformation of heavy metals from active state to inactive state, and reduced the TCLP leaching of heavy metals, thus indicating that Mn-Man could effectively restore the contaminated soil by heavy metals.
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Key words:
- mangosteen shell /
- passivation /
- heavy metals
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表 1 供试土壤基本理化性质
pH SOM
/g·kg−1DOC
/mg·kg−1CEC
/cmol·kg−1砂粒
/%粉粒
/%黏粒
/%Cu
/mg·kg−1Zn
/mg·kg−1Cd
/mg·kg−14.78 30.53 269.68 9.28 21.92 42.21 35.87 1 024.61 975.00 54.33 注:SOM、DOC、CEC分别为土壤有机质、可溶性有机碳、阳离子交换量。 -
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