改性玉米秸秆炭和花生壳炭对溶液中Cd^(2+)的吸附

Adsorption of Cd^(2+) from aqueous solution by modified corn straw biochar and peanut shell biochar

对玉米秸秆和花生壳炭化制备的生物炭,运用高锰酸钾进行改性,研究其对Cd^(2+)的吸附效果。通过批次吸附实验,考察了两种改性生物炭对Cd^(2+)吸附的初始浓度、pH值、接触时间等因素的影响。结果表明,在pH为6.0,Cd^(2+)浓度为100 mg·L^(-1),温度为20℃,吸附时间为12 h,吸附剂投加量为1.0 g·L^(-1)条件下,改性玉米秸秆炭和花生壳炭对Cd^(2+)的去除率分别为67.03%和46.10%,与未改性的生物炭相比,吸附率分别提高了3.8倍和6.2倍。改性玉米秸秆炭和花生壳炭对溶液中Cd^(2+)的吸附均符合Langmuir和Freundlich等温吸附模型,最大吸附量分别为68.97和55.55 mg·g-1。两种改性生物炭的吸附行为均符合准二级吸附动力学模型,说明其吸附以化学吸附为主。改性玉米秸秆炭和花生壳炭吸附Cd^(2+)后,可用NaOH溶液进行解吸,解吸4次后,对Cd^(2+)仍有较好的吸附效果,吸附量分别为31.40和24.10 mg·g^(-1)。这说明,高锰酸钾改性玉米秸秆炭和花生壳炭是一种吸附性能高且能够重复利用的去除溶液中Cd^(2+)的吸附材料。

Biochars produced from corn straw and peanut shell were modified using KMn O4 solution. A laboratory experiment was conducted to investigate the adsorption of Cd^（2＋）in simulated wastewater,and the effects of initial concentrations of Cd^（2＋）,pH values,and contact time on adsorption. Under conditions of pH 6. 0,initial Cd^（2＋）concentration 100 mg·L-1,wastewater temperature 20℃,contact time 12 h,and biochar dosage of 1. 0 g·L-1,modified corn straw biochar and peanut shell biochar achieved cadmium removal rates of 67. 03% and46. 10%,respectively. These removal rates were respectively 3. 8 and 6. 2 times those achieved with unmodified biochars. The adsorption process of modified corn straw biochar and peanut shell biochar can be fitted by Langmuir and Freundlich models. Using the Langmuir equation,the theoretical maximum adsorbance of modified corn straw biochar is 68. 97 mg·g-1and that of peanut shell biochar is 55. 55 mg·g-1. The adsorption process of the two types of biochars could be well described by a pseudo-second-order reaction kinetics model,which indicated that the adsorption was mainly chemical. Cd^（2＋）adsorbed onto the two types of biochar can be easily desorbed by using Na OH solution. After being recycled four times,the two biochars retained 31. 40 and 24. 10 mg·g-1adsorption capacity for Cd^（2＋）. To summarize,corn straw biochar and peanut shell biochar modified by KMn O4 solution have high adsorption capacities for Cd^（2＋）in solution and can beutilized repeatedly.