Efficient Removal of Cu(II), Zn(II), and Cd(II) from Aqueous Solutions by a Mineral-Rich Biochar Derived from a Spent Mushroom (Agaricus bisporus) Substrate

This study evaluated the novel application of a mineral-rich biochar derived from a spent Agaricus bisporus substrate (SAS). Biochars with various pyrolysis temperatures (350-750 degrees C) were used to remove Cu(II), Zn(II), and Cd(II) from aqueous solutions. The adsorption characteristics and removal mechanisms of the biochars were investigated. The adsorption kinetics and isotherm data were fitted well by pseudo-second-order and Freundlich models. The Langmuir maximum removal capacity (Q(max)) values of Cu(II), Zn(II), and Cd(II) were ordered as SAS750 > SAS350 > SAS550, and the Q(max) values of SAS750 were 68.1, 55.2, and 64.8 mg center dot g(-1), respectively. Overall, the removal mechanisms of biochar at a low production temperature (350 degrees C) to Cu(II), Zn(II), and Cd(II) were mainly via ion exchange (54.0, 56.0, and 43.0%), and at a moderate production temperature (550 degrees C), removal mechanisms were mainly via coordination with pi electrons (38.3, 45.9, and 55.0%), while mineral precipitation (65.2, 44.4, and 76.3%, respectively) was the dominant mechanism at a high produced temperature (750 degrees C). The variation of the mutual effect of minerals and heavy metals was the predominant factor in the sorption mechanism of mineral precipitation and ion exchange. The results demonstrated that spent Agaricus bisporus substrate biochar is a potential candidate for the efficient removal of heavy metals, which provides a utilization route for spent mushroom substrates.

Automated summary

This study evaluated the novel application of a mineral-rich biochar derived from a spent Agaricus bisporus substrate for the removal of Cu(II), Zn(II), and Cd(II) from aqueous solutions. The adsorption mechanisms varied with the pyrolysis temperature, with ion exchange dominant at low temperatures, coordination with pi electrons at moderate temperatures, and mineral precipitation at high temperatures. The mutual effect of minerals and heavy metals played a significant role in the sorption mechanism.