Diatomaceous earth incorporated floating magnetic beads for oil removal on water

Abstract

Water contamination by oil spills causes severe damage to the environment and human health. Oil adsorbents should be buoyant, effective oil-contact, and regenerable. In this study, diatomaceous-earth (DE)-incorporated magnetic alginate (Alg)-based beads, chemically modified to include phthalic or maleic anhydride (denoted as Alg/DE/Fe3O4-PA and Alg/DE/Fe3O4-MA), were developed. Internal cavities, formed by cavity-forming agents, made them buoyant. The beads were buoyant and magnetically responsive for 30 days. Maximum oil adsorption capacities of Alg/DE/Fe3O4-PA and Alg/DE/Fe3O4-MA were 29.7 and 21.0 times their weights, respectively. The pseudo-second order kinetics model (R2 ∼0.999, ARE ≤1.088, and χ2 ≤ 0.041) and Freundlich isotherm model (R2 ∼0.999, ARE ≤0.1, and χ2 ≤3.37× 10−3) were used to determine these values. Both beads were magnetically regenerable for up to 20 cycles. DE pores improved oil adsorption capacity by facilitating intra-bead diffusion of surface adsorbed oil. This was confirmed by micro-structural characterization using surface micrographs, elemental distribution, porosity, thermal stability, crystalline phases, molecular vibrational behavior, and magnetic properties. Scanning electron microscopy and X-ray diffractometry analyses revealed spherical beads with well-distributed Fe3O4 spinel on the surfaces. The two adsorbent beads satisfied the criteria for oil-removal from water: buoyancy, high affinity towards various oil types, and magnetic re-collectability.