Extensive analyses of mass transfer, kinetics, and toxicity for hazardous acid yellow 17 dye removal using activated carbon prepared from waste biomass of Solanum melongena

The present study was focused on the synthesis of brinjal waste activated carbon (BWAC) from the dry woody part of brinjal plant by chemical activation method. The BWAC was used as adsorbent to remove acid yellow 17 (AY-17) from the synthetic solution. For BWAC synthesis, phosphoric acid was used as a chemical reagent for chemical activation at a ratio of 1:1, followed by pyrolysis of chemically treated biomass in N 2 atmosphere at high temperatures in a vertical reactor for improved chemical and surface properties of BWAC. The BWAC was characterized by several techniques such as BET surface area, pore distribution, SEM, FTIR, XRD, and point of zero charge (pH PZC ). Various affecting parameters such as equilibrium time, initial pH, BWAC dose, AY-17 concentrations, and temperature for dye removal by BWAC were also investigated in the batch experiment. The maximum of 99.58% removal of AY-17 dye by BWAC occurred at pH 3. More than 97% dye was removed by BWAC from aqueous solution for initial 15 mg/L AY-17 dye concentration with other conditions such as 2 g/L dose, 5.00 ± 0.2 pH, 80 min equilibrium time, and 25 °C temperature. Therefore, further experiments were carried out at pH 5. Equilibrium data were fitted with the isotherm models such as Langmuir, Freundlich, and Temkin, and according to the correlation coefficient ( R 2 ), the Langmuir model was best fitted among them. The experimental kinetic data was well-validated with the pseudo-second-order kinetic model. The mass transfer studies of the dye onto BWAC were described by three models, such as Weber-Morris (intra-particle diffusion), Banghum’s, and liquid film diffusion models, and the result reported that all steps were involved for the adsorption process. The order for the rate-determining step, according to R 2 , was intra-particle diffusion > Bangham’s model > liquid film diffusion model. Recovery and recycling of dye-treated BWAC with desorption efficiency of ~ 73% was possible by 1 M NaOH treatment after 5th cycles. The simulated dye solution after treatment by BWAC was used in seed germination for toxicity assessment.