High-performance biochar from Chlorella pyrenoidosa algal biomass for heavy metals removal in wastewater

Abstract

In this research, a highly porous sodium bicarbonate modified biochar was produced by the fast pyrolysis of Chlorella pyrenoidosa biomass. The biochar without modification showed non-porous material characteristics based on the results of N2 isotherm adsorption–desorption. The modification with sodium bicarbonate successfully enhanced the BET specific surface area of biochar up to 1282 m2/g at a temperature of 750 °C, with microporous surface area of 871 m2/g and external surface area of 411 m2/g. XRD characterization showed broad peak around 24° which indicates amorphous carbon structure that is favorable for adsorption purposes. FTIR characterization after pyrolysis showed an important functional group that should enhance the adsorption process. Following that, a batch adsorption technique of lead synthetic wastewater is used to conduct more tests on its performance. The maximum adsorption capacity of lead (Pb) based on Langmuir model of modified biochar (qmax) is 159.071 ± 23.4008 mg/g. The heterogeneity factor (hf) based on Freundlich model is 0.4671 ± 0.06394, which mainly indicates the physical adsorption. The separation factor (RL) is nearly zero, indicating irreversible nature. The pseudo second order kinetic model showed that the rate of adsorption (k2) for modified biochar is 0.00931 ± 0.00222 g.mg−1 min−1. Overall, the results demonstrated that in terms of technological feasibility, modified biochar from Chlorella pyrenoidosa met the standards of commercial activated carbon, either based on characterization data or performance results.