Adsorption capacity of bio-char prepared from the pyrolysis of hazelnut shells at different temperatures

Abstract

Abstract Biomass pyrolysis to produce bio-char is one of the scientific and effective means of utilizing biomass resources. Differ from previous studies, this paper explored the effect of pyrolysis temperature (400–1000 °C) on the adsorption capacity of hazelnut shell bio-char from two perspectives, including physical macroscopic structure and functional group microscopic adsorption, and the practical adsorption application tests on common 7 kinds of heavy metals in polluted water were further carried out. The results showed that the yield and adsorption of bio-char prepared at different pyrolysis temperatures varied significantly, as the temperature increased, bio-char yield and surface acid functional group content decreased, the adsorption rate on most of heavy metals increased firstly and then decreased (except for Cr6+), the adsorption capacity of bio-char prepared at above 600 °C was mainly affected by physical macroscopic structure, and at 800 °C, bio-char had a large number of pore structures, and pore structure has been fully developed, iodine adsorption value and BET specific surface area were 595.36 mg/g and 197.32 mg/m2, respectively, the adsorption effect of bio-char on Cr6+, Cd2+, Zn2+, Cu2+ and Ni2+ were best, and the adsorption rates were 45.23%, 44.14%, 60.11%, 61.28% and 65.07% respectively. It revealed that although the absorption effect of bio-chars prepared at different temperatures on different heavy metals had a great variation, large specific surface area and developed pore structure still played important role in the adsorption capacity of bio-char. These provided a reference for the application of hazelnut shell bio-char based on adsorption properties, especially absorbing heavy metals in polluted water.