Abstract
Three different types of feedstocks and their biochars were used to remove Cr(III), Cd(II), Cu(II) and Pb(II) ions from a mixture of multiple heavy metals. The effect of the initial concentration of heavy metals in solution has been analysed, and kinetics modelling and a comparison of the adsorption capacity of such materials have been performed to elucidate the possible adsorption mechanisms. The results show that the adsorption capacity is dependent on the type of feedstock and on the pyrolysis conditions. The adsorption capacity of the biomass types is ranked as follows: FO (from sewage sludge)>> LO > ZO (both from agriculture biomass waste)>> CO (from wood biomass waste). Biochars, which are the product of the pyrolysis of feedstocks, clearly improve the adsorption efficiency in the case of those derived from wood and agricultural biomasses. Complexation and cation exchange have been found to be the two main adsorption mechanisms in systems containing multiple heavy metals, with cation exchange being the most significant. The pore structure of biomass/biochar cannot be neglected when investigating the adsorption mechanism of each material. All the disposal biomasses presented here are good alternatives for heavy metal removal from wastewaters.
Highlights
Chromium, copper, cadmium and lead are the main heavy metal species in the wastewater industry[1,2]
LO has been shown to have a higher heavy metal removal efficiency than CO and ZO, which can be explained by the high porosity and the large pore size of LO
The results presented here demonstrate that pore structure is a key factor that can influence the sorption of heavy metals onto biomass, and Bagreev et al reported similar results[24,25,26]
Summary
Copper, cadmium and lead are the main heavy metal species in the wastewater industry[1,2]. Five sorption mechanisms have been proposed to explain biochar adsorption systems, which vary considerably with biochar properties and the target metals. Few studies have compared the sorption capacities of biochar derived from different types of feedstocks via different sorption mechanisms in multiple-heavy-metal systems. Three types of feedstock from wood, agriculture and industrial sewage sludge wastes were used to remove Cr(III), Cd(II), Cu(II) and Pb(II) ions from multiple-metal systems. The objectives of this study are (1) to compare the adsorption capacities of the three different types of feedstocks and derived biochars and (2) to evaluate the possible adsorption mechanisms of biochar in multiple-heavy-metal systems
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