Composites derived from synthetic clay and carbon sphere: Preparation, characterization, and application for dye decontamination

Abstract

Two new composites from synthetic clay-like materials and carbon spheres were developed. Layered doubled hydroxides (LDH) were synthesized from the coprecipitation of Mg²⁺ and Al³⁺ ions. Spherical hydrochar (SH) was prepared from pure glucose through hydrothermal carbonization at 190 °C. The composite LDH-SH was synthesized through a simple hydrothermal method of the mixture of LDH and SH. Another composite, LDO-SB, was directly prepared through the carbonization of LDH-SH at 500 °C. Under such high temperature, LDH was converted to layered doubled oxides (LDO), and SH was transferred to spherical biochar (SB). Those materials were characterized by chemical stability, surface morphology and element composition, crystal structure, surface functional group, and textural characteristic. They were applied for removing cationic dye (methylene blue; MB) and anionic dye (Congo red; CR) under different pH solutions. Three adsorption components—kinetics, isotherm, and thermodynamics—were conducted under batch experimenters. Results demonstrated that the LDH or LDO particles were assembled on the surface of SH or SB, respectively. The surface area, total pore volume, and average pore width of LDH-SH and LDO-SB were 58.5 and 198 m²/g, 0.319 and 0.440 cm³/g, and 21.8 and 8.89 nm, respectively. The maximum adsorption capacity of the materials, calculated from the Langmuir model, at 30 °C for CR and MB dyes was 1589 and 78.6 mg/g (LDO-SB) and 499 and 226 mg/g (LDH-SH), respectively. The composites exhibited a higher affinity to anionic than cationic dyes, which resulted from the great contribution of the clay-like materials. Therefore, they can serve as a promising composite for the decolorization of wastewater.