Modified maize cob powder for zinc and chromium removal from wastewater: predictive modeling and comparative study of mathematical models

This study investigates the removal of zinc and chromium from industrial wastewater using modified maize cob powder as an adsorbent. Various mathematical models were developed through rigorous statistical analysis to describe the adsorption process under different conditions. The effects of adsorbent dosage, contact time, initial heavy metal concentration, pH, and temperature on removal efficiency were examined. For zinc removal, inverse and S-models (R² > 0.941) best described adsorbent dosage effects, while efficiency decreased linearly by 0.545% per mg/L increase in initial concentration (R² = 0.998). Chromium removal showed strong correlations with inverse and quadratic models (R² = 0.941–0.990) for adsorbent dosage, with optimal removal at pH 4–5 following a cubic relationship (R² = 0.984). Temperature significantly impacted both metals, with zinc removal following S-curve dynamics (R² = 0.998) and chromium showing peak efficiency near 40 °C (R² = 0.910). The key novelty lies in developing comprehensive, statistically validated mathematical models that enable precise prediction of heavy metal removal efficiency across multiple parameters, offering a cost-effective alternative to extensive laboratory experimentation. The limitations of this study include specificity to maize cob powder and potential variation under extreme conditions. Future research should validate these models across different adsorbents and multi-component systems.