Nickel ion removal from mine wastewater using eco-friendly activated carbon/Ca(OH)2 from banana Peels: IoT-Based real-time monitoring implemented

Abstract

The increasing demand for nickel in the industrial sector has led to significant Ni²⁺ contamination in the aquatic environment, especially from mine wastewater. This study successfully synthesized eco-friendly biocomposite adsorbents through a blending-thermal method by integrating activated carbon (AC) from ripe (sample 1) and unripe (sample 2) banana peels with Ca(OH)₂ from limestone. The adsorption performance of both biocomposites was evaluated for Ni²⁺ removal from aqueous solutions. The results indicated that the sample 1/Ca(OH)₂ biocomposite attained a removal efficiency of 93 %, marginally surpassing the 92.5 % demonstrated by sample 2/Ca(OH)₂, thereby affirming the enhanced adsorption capacity of AC derived from ripe banana peels. Morphological analysis using SEM revealed distinct surface characteristics; with sample 1 resembling oyster mushroom-like structures and sample 2 exhibiting lettuce-like forms, both possessing marshmallow-like surface textures. IoT-based real-time monitoring showed optimal conditions for Ni²⁺ adsorption at 28–30 °C and low pH. The most significant reduction in absorbance occurred within 200 min due to rapid contact, followed by gradual degradation of pollutants and stabilisation of pH over time. Additionally, the adsorption ability was also attributed to the results of XRD analysis, which showed a decrease in amorphous index with a corresponding increase in crystallinity index upon incorporation of Ca(OH)₂, while FTIR spectra confirmed the increased presence of carbonate groups (CO₃²⁻), which contributed to the enhanced binding of metal ions.