A polymer – zeolite composite for mixed metal removal from aqueous solution

Abstract

Heavy metals become inevitable pollutants that are toxic to life. Lots of treatment methods are available; adsorption is a cheap option. Metals are mostly found as mixtures in wastewaters. Taking this into account, a natural composite adsorbent aims to remove multiple heavy metals (Pb2+, Cu2+, Cd2+). Alginate was combined with clinoptilolite to form alginate – clinoptilolite (A–C) beads. First, factors influencing the removal efficiency of metals were investigated. Then, continuous column experiments were performed to evaluate the real application potential of the adsorbent. A–C beads preferably adsorbed Pb2+. Batch experiments showed metal uptake reached equilibrium after 24 hours and kinetics were compatible with the first-order. Also, pH values near neutral levels were observed to increase heavy metal removal. On the other hand, adsorption equilibrium was well described by the Langmuir model for Cu2+ and Cd2+ and by the Freundlich model for Pb2+. The highest heavy metal uptake was calculated as 2,145 mg /g A–C beads for Pb2+. Continuous column operations were suggested to apply low flow rates (<2 mL/min) and heavy metal concentration (<10 mg/L) for effectiveness. A–C beads can be a good candidate for mixed heavy metal removal composed of environmentally friendly and low-cost materials.

Keywords

• alginate
• cadmium
• clinoptilolite
• copper
• heavy metals
• lead