水葫芦/污泥共热解法制备生物炭粒及其对Cr^3+的吸附特性

Co-Pyrolysis of Water Hyacinth and Sewage Sludge for Preparation of Biochar Particles and Its Adsorption Properties for Cr^3+

为了促进水葫芦和污泥的资源化利用,探究水葫芦/污泥生物炭粒的基本理化性质及其对水中Cr^3+的吸附机制,以水葫芦、污泥为原料,在300~500℃热解温度下制得生物炭粒,通过产率分析、灰分分析、比表面积和孔径分析及SEM(扫描电镜)分析,同时利用吸附动力学模型和等温吸附模型对生物炭粒吸附水中Cr^3+的内在机制进行研究,最后采用TCLP(毒性浸出法)测定了不同生物炭粒中重金属的浸出毒性.结果表明:随着热解温度从300℃升至500℃,生物炭粒的产率从14.93%降至11.75%,生物炭粒的灰分含量逐渐升高,比表面积增大.SEM结果显示,水葫芦与污泥质量比为1∶10时,生物炭粒比表面积较大,孔隙结构明显.当水葫芦与污泥质量比为1∶10、热解温度为500℃时生物炭粒对Cr^3+的吸附量最大,为44.96 mg/g.热力学分析显示,生物炭粒对溶液中Cr^3+的吸附以化学吸附为主,且为单层吸附.TCLP试验表明,水葫芦/污泥生物炭粒中各重金属(Cd、Zn、Cu、Pb、Ni、Cr)的浸出浓度均低于GB 5085.3—2007《危险废物鉴别标准浸出毒性鉴别》的限值.研究显示,添加水葫芦能改善生物炭粒的理化性质,使得生物炭粒对Cr^3+的吸附量增大,以化学吸附为主,且为单层吸附,水葫芦/污泥生物炭粒浸出毒性较低,可为生物炭类环境功能材料的研制提供选材依据.

In order to promote the disposal and utilization of water hyacinth and sewage sludge,explore the basic physicochemical properties of water hyacinth and sludge biochar particles and their adsorption properties for Cr^3+,biochar particles were prepared with water hyacinth and sludge at temperatures of 300,400 and 500℃.The basic physicochemical properties of biochar particles were studied through the analysis of the yield,ash content,specific surface area,pore size analysis and scanning electron microscope(SEM)analysis.Furthermore,adsorption kinetic and isothermal models were used to explore the adsorption mechanism of the biochar particles for Cr^3+in aqueous solution.Finally,the toxic leaching method(TCLP)was used to determine the heavy metal leachability of different biochar particles.The results indicated that the biochar particles yields decreased from 14.93%to 11.75%with the increasing pyrolysis temperature from 300℃to 500℃.However,the ash content and specific surface area of biochar particles increased with increasing pyrolysis temperature.SEM images indicated that the specific surface areas of biochar particles were high and the tubular and pore structure were more obvious when the feedstock ratio of water hyacinth to sewage sludge was 1∶10.The results reveal that the maximum adsorption capacity of the biochar for Cr^3+was 44.96 mg/g at 1∶10 of the ratio of water hyacinth and sludge and 500℃.It was found that the chemisorption was the main mechanism of Cr^3+adsorption,and the adsorption was monolayer adsorption.The TCLP results indicated that the leaching concentrations of all heavy metals were below the limits of Identification Standard for Hazardous Waste Extraction Toxicity Identification(GB 5085.3-2007).The results showed that addition of water hyacinth could improve the physicochemical properties of biochar particles and increase the adsorption capacity of biochar particles for Cr^3+.Chemical and monolayer adsorption was the main adsorption mechanism.The leaching toxicity of water hyacinth sludge biochar particles was lower,which can provide a basis for the selection of raw materials in the development of biochar as environmental and functional materials.