Sustainable and economical dolomite-modified biochar for efficient removal of anionic dyes

Abstract

Dyes induce acute to chronic illnesses in humans and aquatic animals. This study tested dolomite-modified rice husk biochar (DRHB) to eliminate anionic reactive dyes Remazol Brilliant Blue (RBB) and Reactive Black 5 (RB-5) from simulated wastewater solutions. DRHB was produced by pretreating rice husk biomass with the natural mineral dolomite (CaMg(CO3)2) solution following pyrolysis step at 700 °C for 4 h at 8 °C min−1. Pristine rice husk biochar (PRHB) was made by pyrolyzing rice husk for 4 h at 700 °C. The DRHB and PRHB were characterized via different techniques including, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and Scanning electron microscopy (SEM). Afterwards, DRHB was used to get rid of the dyes in the wastewater solutions, and the effects of dose, pH, and contact duration were studied. Both RBB and RB-5 exhibited maximal adsorption capacities of 52.07 and 35.518 mg/g at 50 °C, respectively, and the findings matched well with the Langmuir model, demonstrating monolayer adsorption. For this system, the pseudo-second-order fit is optimal, pointing to chemisorption of both substances. The outcomes presented higher adsorption for RBB (95.63%) compared to RB-5 (85.20%) at 70 mg/L concentration, pH 6, 4 hr. contact time, and 0.3 mg of DRHB dosage. The primary mechanism to remove of both dyes was chemisorption via π-π bond and hydrogen bond. These findings provide insights to build an economical, and sustainable anionic dyes removal technique especially for the third world nations.