Fabrication and characterization of sugarcane bagasse-calcium carbonate composite for the efficient removal of crystal violet dye from wastewater

Sugarcane bagasse (SCB) and calcium oxide with ammonium hydrogen carbonate were reacted in an aqueous solution to obtain an SCB-calcium carbonate (SCB-CaCO3) composite adsorbent, which was used to remove crystal violet (CV) from wastewater. The resulting adsorbent was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction, and surface-area and pore-size analyses. The removal of CV dye by using the SCB-CaCO3 composite adsorbent was investigated at different pH levels, adsorbent dosages, contact times, initial dye concentrations, and temperatures. The equilibrium adsorption capacity of SCB-CaCO3 for CV at 3.33 mg/mL SCB-CaCO3 dosage, temperature of 313 K, pH 9.0, and initial dye concentration 1000 mg/L was 293.02 mg/g, and the corresponding removal rate reached 97.67%. The adsorption isotherms, kinetics, and thermodynamic parameters were evaluated in detail. Results showed that the adsorption isotherms of CV dye were consistent with the Langmuir model, so the adsorption was a monolayer process. The adsorption mechanism of CV can be described by a pseudo-second-order kinetic model, indicating that dye adsorption onto SCB-CaCO3 was primarily affected by strong chemisorption through electrostatic interactions. Further thermodynamic studies revealed that the CV adsorption onto SCB-CaCO3 was a spontaneous and endothermic reaction. We also demonstrated that the adsorption of dye by SCB-CaCO3 involved intraparticle diffusion and hydrogen-bonding interactions to some extent. Overall, SCB-CaCO3 was found to be an efficient, low-cost, green, and recyclable organic dye-removal material.