Biochar is a solid residue produced by thermochemical degradation of biomass. It has a graphitic-like structure and presents different functional groups that are responsible for its chemical properties. Thanks to these interesting characteristics it can be used in several applications, including water remediation, due to its remarkable adsorption capacity of organic and inorganic pollutants [1]. Recent studies have demonstrated that metal adsorption on biochar is influenced by many parameters, e.g. initial concentration and solution pH. A pH variation, indeed, could affect the surface’s charge, metal speciation and, as a consequence, adsorption capacity [2]. All these studies, however, were conducted by setting initial conditions and overlooking the possible pH variations during the tests that could be caused by the adsorption process itself.Aim of this study was the evaluation of the influence of pH and initial metal concentration on adsorption capacity, through Experimental Design approach, for a biochar sample obtained by Miscanthus straw pellets pyrolysis. After a preliminary physical chemical characterization of the sample and determination of its adsorption capacity of Cd2+ and Pb2+, a Central Composite Design was set establishing pH and initial Cd2+ concentration as factors and final metal concentration as response. In order to avoid pH variation during adsorption, pH was maintained steady at the set point chosen by the model. The test have demonstrated that not only pH and concentration influence the system promoting adsorption at high concentration and basic condition, but also that pH tends to vary during adsorption. This variation could be due to basifying characteristics of biochar and protons exchange that could take place when the metal ion is adsorbed on the surface [3].
Metal adsorption on biochar: study of pH influence
BRUZZONITI, Maria Concetta;RIVOIRA, LUCA;FABBRI, DEBORA;
2015-01-01
Abstract
Biochar is a solid residue produced by thermochemical degradation of biomass. It has a graphitic-like structure and presents different functional groups that are responsible for its chemical properties. Thanks to these interesting characteristics it can be used in several applications, including water remediation, due to its remarkable adsorption capacity of organic and inorganic pollutants [1]. Recent studies have demonstrated that metal adsorption on biochar is influenced by many parameters, e.g. initial concentration and solution pH. A pH variation, indeed, could affect the surface’s charge, metal speciation and, as a consequence, adsorption capacity [2]. All these studies, however, were conducted by setting initial conditions and overlooking the possible pH variations during the tests that could be caused by the adsorption process itself.Aim of this study was the evaluation of the influence of pH and initial metal concentration on adsorption capacity, through Experimental Design approach, for a biochar sample obtained by Miscanthus straw pellets pyrolysis. After a preliminary physical chemical characterization of the sample and determination of its adsorption capacity of Cd2+ and Pb2+, a Central Composite Design was set establishing pH and initial Cd2+ concentration as factors and final metal concentration as response. In order to avoid pH variation during adsorption, pH was maintained steady at the set point chosen by the model. The test have demonstrated that not only pH and concentration influence the system promoting adsorption at high concentration and basic condition, but also that pH tends to vary during adsorption. This variation could be due to basifying characteristics of biochar and protons exchange that could take place when the metal ion is adsorbed on the surface [3].
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