Adsorption of Cd(II) and Cu(II) onto Clay Modified with Sludge Activated Carbon
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pISSN 1226-7988, eISSN 1976-3808 www.springer.com/12205
DOI 10.1007/s12205-020-0593-1
Geotechnical Engineering
Adsorption of Cd(II) and Cu(II) onto Clay Modified with Sludge Activated Carbon Kaifan Lia, Haijun Lua, Qian Zhanga, and Jixiang Lia a
School of Civil Engineering and Architecture, Wuhan Polytechnic University, Wuhan 430023, China
ARTICLE HISTORY
ABSTRACT
Received 14 April 2019 Revised 1st 19 October 2019 Revised 2st 7 January 2020 Accepted 23 February 2020 Published Online 28 April 2020
Sludge Activated carbon was prepared by heating dewatered municipal sludge to 400°C using ZnCl2 as an activator. The abilities of clay modified with 1%, 3%, and 5% of the sludge activated carbon to adsorb heavy metals were determined. The materials were subjected to scanning electron microscopy and low-temperature nitrogen-adsorption, extraction efficiency, adsorption kinetics, and isothermal adsorption tests to allow the pore sizes, pore volume distributions, pore structures, and adsorption capacities to be assessed. The pores were mostly mesopores and were mostly amorphous (e.g., ink-bottle-shaped holes). With the solid/liquid ratio kept constant, the adsorption capacity at equilibrium increased as the sludge activated carbon content of the clay increased. For clay modified with 1% sludge activated carbon, the adsorption capacity for Cd(II) at equilibrium decreased from 314 to 280 mg/kg as the solid/ liquid ratio increased from 80 to 160 g/L. The adsorption capacities for Cu(II) at equilibrium at solid/liquid ratios of 80, 120, and 160 g/L were 442, 409, and 383 mg/kg, respectively, which were 41%, 34%, and 37% higher, respectively, than the Cd(II) adsorption capacities at the same solid/liquid ratios. It was concluded that the sludge activated carbon was suitable for trapping heavy metals such as Cd(II) and Cu(II).
KEYWORDS Sludge activated carbon Modified clay Adsorption Heavy metals Pore
1. Introduction Dewatered municipal wastewater sludge is extremely complex. However, sludge is produced around the world, and there is great concern about disposing of sludge without damaging the environment. In China, sludge is currently most often buried, but this can lead to risks to human health and the environment. However, the various ways that may be used to treat sludge are expensive. Modifications of sludge to make it useful or more easily disposed of have been investigated. Sludge has a high organic matter content and contains other potentially useful materials. Sludge activated carbon (SAC) could be a substitute for other forms of carbon. The pyrolysis temperature is key to the SAC yield, and the time and activator used do not directly affect the yield (Agrafioti et al., 2013). In one study, SAC was produced at temperatures between 300 and 700°C, and the three types of SAC produced had different heavy metal adsorption capacities (Wang et al., 2017). SAC prepared using ZnCl2 as an activator had a good adsorption capacity and, at a concentration of 180 g/L, decreased CORRESPONDENCE Haijun-Lu
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