Mechanistic insights and process optimization of pristine corn husk biosorbent for sustainable and cost effective removal of cationic dyes from waste water

Abstract Ensuring safe and accessible drinking water requires effective wastewater treatment. In this work, pristine corn husk biosorbent (CH) was employed as a low-cost material for the removal of Basic Fuchsin (BF) and Crystal Violet (CV) dyes. The CH biosorbent was comprehensively characterized through elemental analysis, scanning electron microscopy (SEM), N₂ adsorption–desorption isotherms, Brunauer–Emmett–Teller (BET) surface area measurements, Fourier transform infrared spectroscopy (FTIR), point of zero charge (pH PZC ), and thermogravimetric analysis (TGA). Batch adsorption studies were carried out to evaluate the influence of various operating parameters, such as CH biosorbent dosage, contact time, temperature, and initial dye concentration. The adsorption kinetics were found to fit the pseudo-second-order model, while the equilibrium isotherm data aligned best with the Langmuir model, showing high correlation coefficients (R² ≥ 0.999) and low error values compared to other tested models. The maximum adsorption capacities were determined to be 77.3 mg/g for BF and 88.8 mg/g for CV. Thermodynamic analysis indicated that the uptake of both dyes onto the CH biosorbent is spontaneous and endothermic. Response surface methodology (RSM) with a central composite design (CCD) was employed to fine-tune the reaction parameters and optimize the adsorption process. The adsorption mechanism is attributed to a combination of electrostatic attraction, π–π stacking, n–π interactions, hydrogen bonding, and pore diffusion. The CH biosorbent demonstrated good reusability, maintaining its performance through five regeneration cycles. Additionally, antibacterial activity tests of the CH biosorbent were conducted before and after dye uptake to assess potential toxicity. The CH biosorbent successfully removed more than 90% of CV and BF from real water samples, highlighting its promise as a sustainable and environmentally friendly biosorbent for water purification.