粉煤灰对含铬废水中六价铬的吸附性能研究

Study on adsorption of Cr(Ⅵ) from chromium containing wastewater by fly ash

由于六价铬的毒性强且易被人体吸收从而对人体健康产生危害,而粉煤灰的吸附效果佳且成本低廉,因而将粉煤灰用于含铬废水的处理技术具有巨大潜力。利用粉煤灰为原材料并对六价铬溶液的吸附效果及作用机理进行初步研究,探究粉煤灰投加量、吸附时间、pH值等单因素对六价铬的吸附性能影响,并对各反应条件再进行响应曲面优化实验,结合吸附动力学模型和吸附等温线模型分析,探讨粉煤灰吸附的最适宜条件和吸附机理。实验结果表明:当粉煤灰的投加量提高至0.6 g时,对六价铬的去除率达到86%;粉煤灰的投加量为0.3 g时,其比吸附量达到最大值14.87 mg/g;在吸附过程的前30 min时其反应速率最快,在pH为2时其吸附效果最佳。通过响应面曲线分析可知,pH值为粉煤灰吸附六价铬离子的主要影响因素,准二级动力学模型的拟合相关系数高达0.9998,说明粉煤灰吸附六价铬的过程主要由化学吸附推动。由吸附等温线实验结果可知,Freundlich模型实验数据拟合度为0.9947,Langmuir模型实验数据拟合度为0.9302。两者相关系数较高,说明整个吸附过程可能属于多相吸附,且包括单分子层吸附。通过对粉煤灰吸附六价铬吸附机理进行研究,为利用废物去除重金属提供了理论依据。

Because ofthe strong toxicity of Cr(Ⅵ) and its easy absorption by human body, Cr(Ⅵ) is harmful to human health, the adsorption effect of fly ash is good and the cost is low, so fly ash can be applied to the treatment of chromium containing wastewater and it has great potential.The adsorption effect and action mechanism of Cr(Ⅵ) solution with fly ash as raw material were preliminarily studied, and the effects of dosage, reaction time and pH on the adsorption performance of Cr(Ⅵ) solution were explored.The response surface optimization experiment was conducted for each reaction condition, and the most appropriate conditions and adsorption mechanism of fly ash adsorption were discussed based on the analysis of adsorption kinetics model and adsorption isotherm model.The experimental results show that when the dosage of fly ash is increased to 0.6 g, the removal rate of hexavalent chromium can reach 86%;when the dosage of fly ash is 0.3 g, its specific adsorption capacity reaches the maximum value of 14.87 mg/g;the reaction rate is fastest in the first 30 minutes of the adsorption process, and the adsorption effect is optimum when the pH is 2.According to the response surface curve analysis, we can see that the pH value is the most important factor for the adsorption of hexavalent chromium ions by fly ash, the fitting correlation coefficient of the Quasi second order dynamic model is as high as 0.999 8,which indicates that the adsorption process of hexavalent chromium ions by fly ash is mainly driven by chemical adsorption.It can be seen from the adsorption isotherm experiment results that the fitting degree of Freundlich model experiment data is 0.994 7,and the fitting degree of Langmuir model experiment data is 0.930 2.The high correlation coefficient indicates that the whole adsorption process may belong to multiphase adsorption, monolayer adsorption is also included.Through the study on the adsorption mechanism of hexavalent chromium by fly ash, a theoretical basis for the removal of heavy metals by waste is provided.