污泥热解残渣对废水中Cr(Ⅵ)去除作用的研究

Study on removal of Cr (Ⅵ) from wastewater with pyrolyzed sludge residue

为探索污泥热解残渣的资源化利用途径,研究污泥热解残渣直接用作吸附剂去除废水中Cr(Ⅵ)的可行性,分析热解温度、时间以及吸附时间、溶液pH值和吸附剂用量等因素对污泥残渣吸附性能的影响。结果表明,在700℃下热解1.0h的污泥残渣的吸附性能最佳,吸附过程可以用准二级反应动力学方程描述;污泥残渣对Cr(Ⅵ)的吸附受多种过程(如化学吸附、颗粒内扩散等)反应速度的影响;Langmuir模型和Freundlich模型均能很好地对试验数据进行拟合,相对而言,吸附行为更符合Langmuir模型;当吸附时间为24.0h,初始溶液pH=4.0,吸附剂质量浓度为20g/L时,污泥残渣对Cr(Ⅵ)的最大吸附质量比q_(max)为13.87mg/g。研究表明,将污泥热解残渣作为廉价吸附剂处理含Cr(Ⅵ)废水有一定的应用前景。

The paper is to present our investigation results on the ability of the low-cost absorbent to remove Cr（VI） from the wastewater by means of pyrolyzed sludge residue. For the given purpose, we have performed batch experiments to explore the influence of the ad- sorption time, solution pH value and adsorbent dosage on Cr（VI） removal rate. The results showed that the properties of the pyrelyzed sludge residue varied with the pyrolysis temperature and time. The scanning electron microscope pictures illustrated porous structure development in the process of pyrolysis. The optimal absorbent with strong adsorption capacity can be obtained by 1.0 h carbonization at the temperature of 700 ℃. The removal rate of Cr（VI） tended to de- crease with the increase of pH value. The removal rate tended to increase with the absorbent dosage increase, but the efficiency of the adsorbent tended to decrease with the increase of its dosage substantially. The Cr（VI） adsorption process could be followed by a pseudo- second-order kinetics model with the rate constant of 6.33 × 10^-2 g/（mg·min）. And as a result, we have found the relation by using intraparticle diffusion model that the diffusion as well as chemical adsorption was related to the Cr（VI） load of the sludge residue. What is more, the Langmuir model and Freundlich model were also found in conformity with the isotherm data, with the former likely proven to be better than the latter. The maximum absorption mass ratio of the residue for Cr（VI） was 13.87 mg/g with pH = 4.0, the adsorption time of 24.0 h, the adsorbent mass concentration of 20 g/L. Thus, the pyrolyzed sludge residue proves to be experimentally developed as a promising adsorbent for Cr（VI） sewage treatment.