不同热解温度生物炭对Pb(Ⅱ)的吸附研究

Effect of the pyrolysis temperature on biochar adsorption of Pb^(2+)

以稻壳(RH)和棉花秸秆(CS)为原料,在300、400、500、600、700℃下制备了生物炭,研究不同添加量、不同初始pH、吸附时间对生物炭吸附水溶液中Pb^(2+)的影响。结果表明:生物炭添加量越大对Pb^(2+)的去除效果越好;热解温度越高,达到同样去除效果所需生物炭的量越少;吸附效果与溶液的pH呈正相关,pH在4~7的范围内,高温生物炭去除Pb^(2+)的效果更好。生物炭对Pb^(2+)的吸附更符合拟二级动力学模型(R^2≥0.992),热解温度越高,吸附速率越快,同时中温(500℃)和高温(600、700℃)生物炭对Pb^(2+)的平衡吸附量不低于49.0 mg·g^(-1)。制备稻壳和棉花秸秆生物炭较合适的温度是500℃。

To investigate the effects of additive amounts, initial pH, and adsorption duration on Pb2＋ adsorption, we prepared the biochars from rice husk and cotton straw at 300, 400, 500, 600, and 700℃. The results showed that the amount of Pb2＋ adsorbed was gradually enhanced with the increasing rate of biochars and was higher with the higher pyrolysis temperature at the same rate of biochars.The adsorption effect was positively correlated with the pH of the solution and better especially in the range of pH 4～7. The fitting curves of Pb2＋ adsorption by biochars were better by the quasi-second-order kinetic model （R2 ≥ 0.992） than the quasi-first-order kinetic model.The higher the pyrolysis temperature, the faster the adsorption rate. Meanwhile, the equilibrium adsorption capacity of Pb2＋ by biochars reached no less than 49.0 mg·g-1 at medium temperature （500℃） and high temperature （600℃ and 700℃）. The suitable temperature for preparing rice husk and cotton stalks is about 500℃.