Adsorption of Cr(Ⅲ) from acidic solutions by crop straw derived biochars

Cr（Ⅲ） adsorption by biochars generated from peanut, soybean, canola and rice straws is investigated with batch methods. Adsorption of Cr（Ⅲ） increased as pH rose from 2.5 to 5.0. Adsorption of Cr（Ⅲ） led to peak position shifts in the FFIR-PAS spectra of the biochars and made zeta potential values less negative, suggesting the formation of surface complexes between Cr^3＋ and functional groups on the biochars. The adsorption capacity of Cr（Ⅲ） followed the order： peanut straw char 〉 soybean straw char 〉 canola straw char 〉 rice straw char, which was consistent with the content of acidic functional groups on the biochars. The increase in Cr^3＋ hydrolysis as the pH rose was one of the main reasons for the increased adsorption of Cr（Ⅲ） by the biochars at higher pH values. Cr（llI） can be adsorbed by the biochars through electrostatic attraction between negative surfaces and Cr^3＋, but the relative contribution of electrostatic adsorption was less than 5%. Therefore, Cr（Ⅲ） was mainly adsorbed by the biochars through specific adsorption. The Langumir and Freundlich equations fitted the adsorption isotherms well and can therefore be used to describe the adsorption behavior of Cr（Ⅲ） by the crop straw biochars. The crop straw biochars have great adsorption capacities for Cr（Ⅲ） under acidic conditions and can be used as adsorbents to remove Cr（Ⅲ） from acidic wastewaters.

铝改性秸秆生物质炭去除水体中的大肠杆菌

用一次平衡实验和柱淋溶实验研究了秸秆生物质炭和铝改性秸秆生物质炭对水中大肠杆菌的吸附量和去除率。结果表明,未改性秸秆生物质炭对大肠杆菌的吸附量很低,铝改性秸秆生物质炭对大肠杆菌有很高的吸附容量和去除率,0.6 mol/L Al(Ⅲ)改性生物质炭对大肠杆菌的去除效果优于0.3 mol/L Al(Ⅲ)改性生物质炭。当大肠杆菌浓度低于0.63 mg/ml时,铝改性大豆秸秆炭对大肠杆菌的去除率达100%,铝改性花生秸秆炭和铝改性稻草炭对大肠杆菌的去除率在96%和90%以上。0.5 mg/ml的大肠杆菌悬液通过装有2 g铝改性稻草炭的淋溶柱,每次收集10 ml淋出液,共收集152次,大部分淋出液中大肠杆菌浓度小于0.02 mg/ml,大肠杆菌去除率在95%以上。因此,铝改性生物质炭可用于水体中大肠杆菌的去除。