Effective removal of Cr(VI) and Pb(II) ions from mining wastewater using eco-friendly synthesized magnesium oxide nanoparticles incorporated rice husk ash

Abstract

This study explored the effective adsorptive performance of magnesium oxide (MgO) nanoparticles incorporated rice husk ash (RHA) to address the removal of Chromium (VI) and Lead (II) from mining wastewater from aqueous environment. MgO nanoparticles were synthesized using a magnesium salt precursor and moringa oleifera leaf extract and then impregnated onto RHA to create MgO-RHA nano composite. Different analytical techniques were employed to characterize the RHA and MgO-RHA nanocomposites. The prepared adsorbents were used in batch adsorptive studies and the concentrations of the metal ions were measured before and after treatment using atomic absorption spectrophotometry. Morphological analysis confirmed that the adsorbents developed exhibited a dispersed and porous nature. BET analysis revealed that RHA, MgO, and MgO-RHA had surface areas of 93.04, 32.02, and 102.71 m²/g, respectively. MgO-RHA outperforms RHA in removing metal ions due to its increased surface area and functionality. MgO-RHA demonstrated higher removal percentages of up to 79.20 % and 96.02 % for Cr(VI) and Pb(II), respectively. The Pseudo-second order kinetics and Langmuir isotherm demonstrated the highest degree of conformity to the experimental data, considering the coefficient of determination (R²), smallest value of SSE and chi-square (ᵪ2). Thermodynamic results indicated that the adsorption process was characterized by endothermicity, spontaneity and chemisorption controlled. In summary, the performance of the MgO-RHA nanocomposite surpassed that of RHA alone, which serves as a better adsorbent for metal ion removal.