Adsorption of heavy metals from acid mine drainage using poly (hydroxamic acid) ligand

Abstract

Acid mine drainage (AMD) causes severe environmental concerns worldwide due to its high acidity, toxic metals and sulphate contents. Conventional treatment methods may not be effective for AMD. There is a need for wastewater remediation; however, it requires cost-effective technologies for efficiently removing heavy metals. The current study reports the remediation of AMD using a modified pine cone powder. The surface of the biosorbent was improved by pre-treatment using Fenton reagent and then modified using chemical grafting of acrylic acid onto pine cone powder with free radical initiation. The modified adsorbent was used for adsorption of (Fe3+), (Cu2+), (Mn2+), (Zn2+), and (Pb2+) from single components solution and acid mine drainage sampled from an abandoned mine at Witbank. The adsorption behaviour of poly (hydroxamic acid) ligand has been studied to determine its application in treating Witbank acid mine drainage (AMD). The rate of adsorption and the uptake at equilibrium were investigated using batch conditions from single and multi-component solutions (AMD). The optimum pH for the poly (hydroxamic acid) ligand was 6 for all heavy metal ions investigated with the percentage removal of 79,83, 82,90 and 73% for Fe3+, Cu2+, Mn2+, Zn2+ and Pb2+ respectively. The ligand's binding capacity (qe) with metal ions such as iron, copper, manganese, zinc and lead were 13, 14, 11, 11 and 12 mg g−1, respectively. The adsorption of the heavy metal ions onto the ligand fitted well with the Langmuir isotherm model due to R2 > 0.99 compared to the Freundlich model. Additionally, RL values were in a range of 0,0020 to 0,0560, which indicates favourable adsorption. Furthermore, pseudo second-order kinetics was the best to describe adsorption kinetics for AMD metal ions using poly (hydroxamic acid) ligand. The AMD treatment using poly (hydroxamic acid) ligand showed great potential as a low-cost alternative material.