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/Fe 3 O 4 -PA and Alg/DE/Fe 3 O 4 -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/Fe 3 O 4 -PA and Alg/DE/Fe 3 O 4 -MA were 29.7 and 21.0 times their weights, respectively. The pseudo-second order kinetics model ( R 2 ∼ 0.999, ARE ≤ 1.088, and χ 2 ≤ 0.041) and Freundlich isotherm model ( R 2 ∼ 0.999, ARE ≤ 0.1, and χ 2 ≤ 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 Fe 3 O 4 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. • The Alg/DE/Fe 3 O 4 -PA with high buoyancy has been prepared for oils removal. • The DE and PA improved stability and q max of Alg/Fe 3 O 4 towards oils. • Oil removal was rapid and less affected by type of water, pH, and temperature. • Recovery of oil-loaded Alg/DE/Fe 3 O 4 -PA can be simply achieved by using a magnet. • The Alg/DE/Fe 3 O 4 -PA exhibited stable adsorption performance for up to 20 cycles.
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