Efficient low-cost magnetic composite based on eucalyptus wood biochar for arsenic removal from groundwater

Abstract

Low-cost, eco-friendly and efficient charcoal-based composites have been developed to remove arsenic from two Argentine naturally contaminated groundwater samples. Iron compounds have been added to the charcoals both to enhance the composites’ sorption capacities and to provide permanent magnetization to the materials. The raw charcoals, one made from eucalyptus wood charcoal (EWC) and a commercial activated carbon (CSC), as well as their magnetic variants (MEWC and MCSC, respectively), have been characterized by several techniques and tested for arsenic sorption. In the magnetic analogues, Mössbauer spectroscopy enabled the identification of magnetite as the main Fe oxide together with some paramagnetic Fe phases and goethite. The magnetization saturation values of 11.2 ± 0.5 Am2 kg−1 for MEWC and 10.7 ± 0.5 Am2 kg−1 for MCSC agree with Mössbauer results. These saturation values indicate that it is possible to separate the sorbents from the liquid phase with an external magnetic field. Arsenic removal was higher for MEWC than for MCSC, and arsenic sorption from naturally contaminated water samples resulted lower than in the synthetic one. For natural waters, As residual concentrations resulted lower than 50 μg L−1, which is the limit for drinking water in Argentina. The satisfactory results achieved for the homemade eucalyptus-derived composite indicate that it is a promising material to be used in simple technological systems for water treatment.