小麦秸秆生物炭对水中对羟基苯甲酸乙酯的吸附特性

Adsorption characteristic of ethyl paraben from aqueous solution using wheat straw biochar

对羟基苯甲酸乙酯属于尼泊金酯类物质,是一种典型的新兴环境污染物.本研究通过制得不同热解温度(300、500和700℃)下的小麦秸秆生物炭(分别表示为BC300、BC500、BC700),对水中对羟基苯甲酸乙酯进行间歇吸附.结果表明,热解温度升高会导致生物炭表面疏水性增强,且引起零电荷点从8.37升至9.42.溶液初始p H值由8升至12时,对羟基苯甲酸乙酯去除率显著递减;此外,溶液离子强度的增强会导致对羟基苯甲酸乙酯去除率的下降.生物炭吸附水中对羟基苯甲酸乙酯的等温吸附过程符合Langmuir方程,其中,最大吸附容量排序为:BC700>BC500>BC300.同时,吸附过程符合准二级动力学方程,且为吸热自发过程.此外,经过4轮再生吸附,生物炭吸附容量仍可达到最初的90%,其中,BC700展示出最高的吸附效率(92.76%).

As a representative emerging pollutant of parabens,ethyl paraben was subject to batch adsorption in aqueous medium by wheat straw-pyrolyzed biochars at 300,500 and 700 ℃,which are named BC300,BC500,and BC700,respectively. Results show that greater pyrolysis temperature enhanced the hydrophobicity of biochar and increased the point of zero charge of biochar from 8.37 to 9.42. In addition,alkaline conditions（ hydrophobic p H = 8 ~12） decreased the adsorption capacity significantly. Also,greater ionic strength weakened the adsorption capacity. Sorption isotherm of ethyl paraben agrees well with Langmuir isotherm model,and the order of maximum adsorption capacities is BC700BC500BC300.Adsorption kinetics is well described by the pseudo-second-order model,and the adsorption processes are endothermic and spontaneous. After 4 cycles of adsorption-regeneration test,the regenerated biochars still maintained 90% of their initial adsorption capacities,and BC700 showed the largest recovered adsorption capacity,which is92.76% of its initial adsorption capacity.