Novel calcium lactate-activated biochar derived from corn straw for tenuazonic acid removal: Adsorbent preparation, adsorption mechanisms, and real application

Abstract

Alternaria in contaminated agricultural products can produce highly toxic tenuazonic acid (TeA). Due to its teratogenic, mutagenic, and carcinogenic effects, TeA seriously threatens human health. In this study, we synthesized a novel calcium lactate-modified adsorbent based on corn straw biochar (CLBC0.25-800) and investigated its performance in the removal of TeA from an aqueous solution and apple juice. CLBC0.25-800 was obtained using corn straw powder mixed with Ca lactate at a ratio of 1:4 and heated at 800℃ for 2 h, producing a large specific surface area (SSA) of 215.4440 m²∙g⁻¹ and pore volume of 0.1510 cm³∙g⁻¹. The large pore volume and large SSA, rich and irregular pore structure, and tubular cavity structure of CLBC0.25-800 were conducive to TeA adsorption. Batch experiments were conducted under different adsorbent doses, initial TeA concentrations, temperatures, and contact times. The results showed that 3 g/L of CLBC0.25-800 reacted with 25 mL of 0.100 mg/L TeA solution for 60 min achieved a high adsorption capacity of 0.0315 mg/g and a removal efficiency of 94.6 %. Moreover, to reveal the adsorption mechanism of CLBC0.25-800 for TeA, we studied the adsorption kinetics, isotherms, and thermodynamics. TeA was adsorbed on CLBC0.25-800 through pore adsorption, complexation between Ca²⁺ and TeA, and π–π interactions. The adsorption process was primarily homogeneous monolayer physical adsorption with secondary chemisorption. CLBC0.25-800 successfully adsorbed TeA in spiked apple juice without significant effects on the contents of sugar and organic acids. The findings provided a new strategy to adsorb TeA.