Removal of chlorpyrifos from waste water by wheat straw-derived biochar synthesized through oxygen-limited method

Abstract

Systematic studies have been performed for the first time to investigate the pyrolysis behavior of wheat straw and the adsorption mechanism of chlorpyrifos by wheat straw-derived biochar. FTIR and elemental analysis indicated that aromatic and hydrophobic substances are produced during the pyrolysis process of wheat straw. The BET results suggested that the pyrolysis temperature of wheat straw should be above 450 °C to acquire the biochar with a surface area above 60.0 m² g⁻¹. The adsorption experiments show that wheat straw-derived biochar at 750 °C (WS750) can effectively adsorb chlorpyrifos and the largest adsorption quantity is 16 mg g⁻¹. The driving force for chlorpyrifos adsorption by WS750 is most likely attributed to the π⋯π stack between the aromatic ring of chlorpyrifos and these aromatic areas on WS750 surface. The adsorption behaviors follow the pseudo-second kinetic and Freundlich models. Recycle experiments show that the adsorption ability of WS750 can be recovered by washing with methanol. The present study shows that wheat straw-derived biochar can work as a highly effective and low-cost adsorbent to remove chlorpyrifos from waste water.