title: Metal immobilization by sludge-derived biochar: roles of mineral oxides and carbonized organic compartment.
abstract: Pyrolyzing sludge into biochar is a potentially promising recycling/disposal solution for municipal wastewater sludge, and the sludge-derived biochar (SDBC) presents an excellent sorbent for metal immobilization. As SDBC is composed of both mineral oxides and carbonized organic compartment, this study therefore compared the sorption behaviour of Pb and Zn on SDBC to those of individual and mixture of activated carbon (AC) and amorphous aluminium oxide (Al2O3). Batch experiments were conducted at 25 and 45 °C, and the metal-loaded sorbents were artificially aged in the atmosphere for 1-60 days followed by additional sorption experiments. The Pb sorption was generally higher than Zn sorption, and the co-presence of Pb reduced Zn sorption on each studied sorbent. Higher sorption capacities were observed at 45 °C than 25 °C for SDBC and AC, while the opposite was shown for Al2O3, indicating the significance of temperature-dependent diffusion processes in SDBC and AC. Nevertheless, metal sorption was more selective on Al2O3that showed a greater affinity towards Pb over Zn under competition, correlating with the reducible fraction of sequential extraction. Furthermore, significant amounts of Pb and Zn were additionally sorbed on SDBC following 30-day ageing. The X-ray diffraction revealed the formation of metal-phosphate precipitates, while the X-ray photoelectron spectroscopy showed a larger quantity of metal-oxygen bonding after 30-day ageing of metal-loaded SDBC. The results may imply favourable long-term transformation and additional sorption capacity of SDBC. In conclusion, SDBC resembles the sorption characteristics of both organic and mineral sorbents in different aspects, presenting an appropriate material for metal immobilization during soil amendment.
authors.affiliation: School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou, 510275, China.|Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Guangzhou, 510275, China.
authors.forename: Weihua
authors.initials: W
authors.lastname: Zhang
authors.affiliation: School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou, 510275, China.
authors.forename: Xinchen
authors.initials: X
authors.lastname: Huang
authors.affiliation: School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou, 510275, China.
authors.forename: Yanming
authors.initials: Y
authors.lastname: Jia
authors.affiliation: Laboratoire Sols et Environnement, UMR 1120, Université de Lorraine, 2, avenue de la Forêt de Haye, TSA 40602, 54518, Vandoeuvre-lès-Nancy cedex, France.|Laboratoire Sols et Environnement, UMR 1120, INRA, 2, avenue de la Forêt de Haye, TSA 40602, 54518, Vandoeuvre-lès-Nancy cedex, France.
authors.forename: Frederic
authors.initials: F
authors.lastname: Rees
authors.affiliation: Department of Civil and Environmental Engineering, Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China.
authors.forename: Daniel C W
authors.initials: DC
authors.lastname: Tsang
authors.affiliation: School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou, 510275, China.|Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Guangzhou, 510275, China.
authors.forename: Rongliang
authors.initials: R
authors.lastname: Qiu
authors.affiliation: School of Environmental Science and Engineering, Southern University of Science and Technology, Shenzhen, 518055, China. wangh6@mail.sustc.edu.cn.
authors.forename: Hong
authors.initials: H
authors.lastname: Wang
mesh_terms: D000537:Aluminum Oxide / Q000737:chemistry; D002606:Charcoal / Q000737:chemistry*; D007854:Lead / Q000737:chemistry; D008670:Metals / Q000737:chemistry*; D008903:Minerals / Q000737:chemistry; D056951:Photoelectron Spectroscopy; D012722:Sewage / Q000737:chemistry*; D013696:Temperature; D013997:Time Factors; D018505:Waste Management / Q000379:methods; D014961:X-Ray Diffraction; D015032:Zinc / Q000737:chemistry
chemical_list: D008670:Metals; D008903:Minerals; D012722:Sewage; C540010:biochar; D002606:Charcoal; D007854:Lead; D015032:Zinc; D000537:Aluminum Oxide
keywords: Activated carbons; Metal sorption; Mineral oxides; Sludge-derived biochar