Pristine corn kernels as a pH-responsive biosorbent for selective removal of cationic and anionic dyes

Wastewater treatment is of utmost importance in providing equitable and safe drinking water. The present study uses pristine corn kernel (CK) biosorbent to remove the anionic Acid Green 20 (AG20) and the cationic Crystal Violet (CV) dyes from different water samples. The CK biosorbent was thoroughly characterized with elemental analysis, Scanning electron microscopy (SEM), N₂ adsorption/desorption isotherm, Brunauer-Emmett-Teller (BET), Fourier transform infrared spectroscopy (FTIR), point of zero charge (pH_PZC), and Thermogravimetric analysis (TGA). The adsorption of dyes onto CK biosorbent was studied in batch and column modes. The experimental variables influencing the adsorption process were evaluated including the dose of CK biosorbent, contact time, pH, temperature, and initial dye concentration. The adsorption process is best described by the pseudo-second-order kinetic and Langmuir isotherm models with maximum adsorption capacities of 85.74 and 61.1 mg/g for AG20 and CV, respectively. The thermodynamic studies revealed that the adsorption of AG20 and CV dyes onto CK biosorbent is spontaneous and endothermic. The CK biosorbent can be regenerated successfully up to five cycles. Furthermore, the antibacterial activity studies of CK before and after dye binding were performed to assess the toxicity of these materials. The CK biosorbent was successfully used to remove CV and AG20 from real water samples with a recovery % more than 90%. The plausible adsorption mechanism of AG20 and CV onto CK biosorbent is proposed due to pore diffusion, electrostatic interactions, π-π interactions, n-π interactions and hydrogen bonds.