Biochar MMT ZnAl LDH composite materials derived from solid waste for heavy metal removal in artificial acid mine drainage
Yudha Gusti Wibowo, Hana Safitri, Kusumawati Kusumawati, Wahyu Dera Aini, Richar Farantino, Simparmin Br Ginting, Asnan Rinovian, Setyo Budi Kurniawan, Khairurrijal Khairurrijal, Tarmizi Taher, Wida Banar Kusumaningrum, Sudibyo Sudibyo, Ahmad Tawfiequrahman Yuliansyah, Himawan Tri Bayu Murti Petrus
Abstract
This study investigates the synthesis and performance of a biochar-based composite, integrating montmorillonite (MMT) and ZnAl layered double hydroxide (LDH), for the removal of Fe and Mn from acid mine drainage. The biochar_MMT_ZnAl LDH composite, synthesized from solid waste materials, was characterized using BET, XRD, FTIR, TGA, and SEM-EDS analyses. The material demonstrated a surface area of 117.54 m 2 /g and a pore volume of 0.21 cm 3 /g, significantly surpassing non-composite biochar with a surface area of 14.81 m 2 /g. The batch sorption experiment showed rapid adsorption kinetics, achieving 99% Mn removal within 7 min at 0.5 g adsorbent dosage, reducing Mn concentration from 100 mg/L to 0.07 mg/L. For Fe, an 87% reduction was achieved after 400 min using 0.5 g of plain biochar, while biochar_MMT_ZnAl LDH showed superior adsorption performance with a final Fe concentration below 0.07 mg/L. Adsorption isotherm analysis indicated that biochar followed the Dubinin–Radushkevich model, while the composites adhered to the Redlich–Peterson model. Kinetic studies revealed a strong fit with the Pseudo-Second-Order model (R 2 = 1 for biochar_MMT), suggesting chemisorption as the dominant mechanism. Thermodynamic analysis confirmed the spontaneity and endothermic nature of the adsorption process, with ΔG values ranging from − 18,758 to − 92,932 J/mol for Fe and Mn removal. The findings highlight the potential of biochar-based composites in developing cost-effective and environmentally sustainable solutions for acid mine drainage treatment.