生物炭-锰氧化物复合材料对红壤吸附铜特性的影响

锰氧化物作为改性材料应用于制造复合材料一直是环境领域的研究热点,锰氧化物改性的复合材料在水处理、空气清新剂等领域应用广泛。但目前,将生物炭-锰氧化物复合材料作为吸附材料改变土壤对铜吸持能力的研究还不多见。采用等温平衡吸附法,测定生物炭-锰氧化物复合材料对红壤吸附铜的能力影响,并应用Freundlich方程Cs=KfCen分析红壤对铜的吸附特征。结果表明：不同用量的生物炭-锰氧化物复合材料加入后,均会明显提高红壤对铜的吸附量。添加0.5%、1.0%、2.0%和4.0%生物炭-锰氧化物复合材料的红壤处理,其铜的吸附量较未添加处理分别增加了63.1%、130%,310%和509%。Freundlich吸附方程能较好的描述不同用量生物炭-锰氧化物复合材料影响红壤对铜的吸附特征。添加0.5%、1.0%、2.0%和4.0%炭-锰材料处理的分配系数（Kf值）分别为0.176、0.286、0.653和0.800。生物炭-锰氧化物复合材料用量为4.0%时,分配系数（Kf值）较对照红壤提高了5倍,生物炭-锰氧化物复合材料加入红壤后对红壤pH值影响不大,对CEC（阳离子交换量）有较大的影响;生物炭-锰氧化物复合材料用量为4.0%时,CEC为5.59 cmol·kg-1,较对照增加了14.1%,温度升高,有利于提高红壤对铜的吸附能力。生物炭-锰氧化物复合材料加入红壤后,红壤在1034.63、537.22、471.45 cm-1处有吸收峰出现,红壤表面-OH、Mg-O、Si-O等活性官能团数量明显增加。生物炭-锰氧化物复合材料增加红壤对铜的吸附机制可能是红壤表面Mg-O、Si-O等官能团与铜形成了Mg-O-Cu-、Si-O-Cu-络合物,提高了红壤对铜的吸持能力。从土壤化学与土壤修复的角度出发,生物炭-锰氧化物复合材料可用于铜污染红壤修复。

Effects of biochar-manganese oxides composite on adsorption characteristics of Cu in red soil

As the modified material, manganese oxide used in manufacturing composite is a hot research topic for environmental field. The manganese oxide modified composite was widely applied to water treatment, air fresheners, and so on. However, there were few reports on changing sorption characteristics of copper in soil with biochar-manganese oxide composite as adsorption materials. In the present study, the sorption batch experiments were employed to investigate the effects of biochar-manganese oxides composite on copper sorption in red soils. Freundlich equation was used to characterize the sorption of copper and calculate distribution coefficients. The results showed that the adsorption of Cu increased significantly by adding biochar-manganese oxides composite. Compared to the non biochar-manganese oxides composite system, the percentages of Cu adsorption increased 63.1%, 130%, 310%, and 509% with adding 0.5%, 1.0%, 2.0%, and 4.0% of biochar-manganese oxides, and their distribution coefficient （Kf） were 0.176, 0.286, 0.653, and 0.800, respectively. Among all dosages, the distribution coefficients were five times at 4.0% of biochar-manganese oxides higher than that at no adding composite materials. There was little effect on red soil pH value after adding biochar-manganese oxide composite, while, the CEC （Cation Exchange Capacity） were great influenced, especially, the dosage of biochar-manganese oxide composite was 4.0%, and CEC was 5.59 cmol.kg-1, increasing by 14.1%. The absorption peak were measured at 1034.63, 537.22, 471.45 cm-1 and the activity functional groups such as -OH, Mg-O, Si-O increased significantly in red soil after adding biochar-manganese oxide composite. Due to the complex such as Mg-O-Cu- and Si-O-Cu- were formed in red soil surface, the copper adsorption capacity of red soil was improved. It was demonstrated that biochar-manganese oxide composite could be considered as a promising material to immobilize heavy metal-contaminated soils.