Adsorption of congo red using carbon from leaves and stem of water hyacinth: equilibrium, kinetics, thermodynamic studies

The present study investigates carbon synthesized from water hyacinth stem and leaf as an adsorbent for the effective removal of congo red dye from aqueous solution. The synthesized adsorbents was characterized by scanning electron microscopy, Brunauer–Emmett–Teller surface area, Fourier transform infrared spectroscopy, and point of zero charge. The effect of different parameters, i.e. adsorbent dosage, contact time, pH of solution, initial dye concentration, and temperature, was studied in detail. The experimental data were construed and studied using Langmuir, Freundlich and Temkin isotherms. The Langmuir isotherm was observed to be best fit with maximum adsorption capacities of 14.367 mg/g and 13.908 mg/g at 50 °C and a contact time of 60 min and initial dye concentration of 50 mg/L for carbon from water hyacinth stem and leaf. The adsorption of congo red onto the carbon synthesized from water hyacinth stem and leaf follows the second-order kinetics, with the R 2 values being close to 1. The results show that carbon synthesized from water hyacinth stem and leaf can be a viable adsorbent for the removal of congo red dye from wastewater in a low-cost and environmentally friendly approach. Graphical abstract