生物炭-锰氧化物复合材料吸附砷(Ⅲ)的性能研究

Adsorption of Arsenic(Ⅲ) on Biochar-manganese Oxide Composites

以生物炭为对照,采用吸附试验,考察了炭-锰复合材料和生物炭对砷(Ⅲ)的吸附性能,应用Langmuir、Freundlich方程和吸附动力学方程分析了其对砷(Ⅲ)的吸附特征,并结合不同时间、吸附剂加入量及p H条件下对砷的吸附效果来探讨其吸附性能。结果表明,生物炭与炭-锰复合材料对砷(Ⅲ)的吸附均较迅速,在30 min内对砷(Ⅲ)的吸附即可达到最大,且吸附过程较符合准二级动力学方程(R2>0.99)。利用粒子分散模型进行拟合,发现炭-锰复合材料和生物炭吸附过程符合多过程吸附模型,炭-锰复合材料对砷的吸附能力明显提高,最大吸附容量从11.41 mg·g-1(生物炭)增加到20.08 mg·g-1(炭-锰复合材料),其吸附机制可能是炭-锰复合材料中的锰氧化物增加了复合材料表面的吸附位点;p H在3~7的范围内对复合材料吸附砷的影响作用不大。实验结果表明,炭-锰复合材料是一种很有发展前景的功能吸附材料。

Both biochar and manganese oxide are good adsorbents for metals. However there is little information about metal adsorption on their composited material. In this study, the adsorption of arsenic(Ⅲ)on manganese oxide-modified biochar was investigated under different contact time, adsorbent doses and solution p H, using batch adsorption method. The arsenic(Ⅲ)adsorption on both unmodified biochar and biochar-manganese oxide composite was rapid, reaching adsorption equilibrium within 30 min. The adsorption behavior could be well described with pseudo-second-order kinetic equation with a R2>0.99. The adsorption process appeared to be a multistep process that could be fitted with an intraparticle diffusion model. The maximum capacity of arsenic(Ⅲ)adsorption increased from 11.41(unmodified biochar)to 20. 08 mg·g-1(manganese oxide modified biochar), which should be attributed to the increase of adsorption sites on the surface of biochar-manganese oxide composite due to the presence of manganese oxides. The effect of solution p H on arsenic(Ⅲ)adsorption was negligible in p H 3~7. The present results show that biochar-manganese oxide composite is a promising functional adsorbent as it is easy to be synthesized and works well in a wide p H range.