Comparative assessment of Al2O3 modified biomasses from agricultural residues for nickel and cadmium removal

The biodiversity of aqueous environments has been affected due to the disposal of wastewater highly contaminated with heavy metal ions, causing much damage to ecosystems. These pollutants are very toxic and bioaccumulate in living organisms. This work attempts to evaluate the adsorption of nickel ad cadmium ions using three biomasses from agricultural residues (corn cob – CC, orange peel – OP, and oil palm bagasse – PB) modified with alumina nanoparticles. The biomasses were characterized via compositional analysis and a point of zero charges to quantify the presence of lignin, cellulose, hemicellulose, and the feasible pH, taking advantage of the biomass charge. After modification with Al2O3 nanoparticles. The resulting adsorbents were characterized via FT-IR analysis to identify the functional groups that most contributed to the adsorption performance. Furthermore, the influence of Al2O3 nanoparticles was analysed on the adsorption capacities of the evaluated biomasses using batch systems at a temperature of 25°C and pH 6. All biomasses displayed a high content of cellulose, estimating a weight percentage of about 19.9%, 14.3%, and 13.1% for PB, OP, and CC samples, respectively. The FT-IR spectrum confirmed hydroxyl and carboxyl functional groups, which contribute to enhancing the adsorption capacities of the modified biomasses. Functional adsorption capacity was observed for all biomasses after modification with Al2O3 nanoparticles, achieving at pH 6.0 a cadmium removal from 92% (CC-Al2O3 and PB-Al2O3) up to 95.8±0.3% (OP-Al2O3). In nickel ions, it was estimated a broader adsorption capacity at pH 6.0 of about 86±0.4% after using the CC-Al2O3 sample, 88±0.1% for the PB-Al2O3 adsorbent, and 98±0.2% for the OP-Al2O3 sample, confirming the suitability of these Al2O3-modified biomasses for the removal of heavy metal ions.