Fe₃O₄ nanoparticle-coated mushroom source biomaterial for Cr(VI) polluted liquid treatment and mechanism research

Agrocybe cylindracea substrate-Fe₃O₄ (ACS-Fe₃O₄), a Fe₃O₄ nanoparticle-coated biomaterial derived from agriculture waste from mushroom cultivation, was developed to remove hexavalent chromium (Cr(VI)) from liquid. After modification, material surface became uneven with polyporous and crinkly structure which improved Cr-accommodation ability in a sound manner. Optimized by the Taguchi method, Cr(VI) removal percentage was up to 73.88 at 240 min, 40°C, pH 3, Cr(VI) concentration 200 mg l^-1, dosage 12 g l^-1, rpm 200. The efficient Cr(VI) removal was due to the combined effect of adsorption and redox. In addition, verification test using tannery wastewater, with removal percentage of Cr(VI) and total Cr reaching 98.35 and 95.6, provided further evidence for the efficiency and feasibility of ACS-Fe₃O₄. The effect of storage time of the material on Cr(VI) removal was small, which enhanced its value in practical application. Results indicated that metal removal was mainly influenced by solution concentration, adsorbent dosage and treatment time. The experimental data obtained were successfully fitted with the Langmuir isotherm model. Thermodynamic study indicated the endothermic nature of the process. The results confirmed that ACS-Fe₃O₄ as novel material derived from waste, with long-term stability, could be applied for heavy metal removal from wastewater and waste cycling.