Recycled plastics as innovative low-cost adsorbents to reduce lead concentrations in waters

Abstract

Plastic wastes are an issue of global concern due to their continuous increase and their negative impact in the environment, but recycling rates are still low. The search of new uses for recycled plastics could increase these rates extending the product life cycle. Several works have shown the capacity of plastics to adsorb contaminants from the surrounding environment. This capacity could be an advantage to use plastics as innovative and low-cost adsorbents materials in solid phase extraction systems to reduce the contaminant load in effluents. Then, the aim of this work was to evaluate the use of recycled plastics as low-cost adsorbents to reduce the metals load in effluents. The adsorption capacity of three different recycled plastics, high density polyethylene (HDPE), low density polyethylene (LDPE) and polypropylene (PP), for Pb2+ in water was evaluated. After material characterization, the effect of several parameters on the adsorption efficiency was tested, as sample pH, sorbent dosage, contact time, initial Pb2+ concentration and co-existing metals ions and organic matter. In addition, a continuous flow system was also proved, as well as the possibility of reuse the adsorbent several times. The results suggest that recycled plastics, as obtained from the recycling plant, can be a good low-cost alternative to reduce the lead concentrations in effluents before they were discharged to the environment, allowing a reduction up to 70 % of lead even when a continuous flow solid phase extraction system is used. Besides, developing countries could take advantage of a widely available and low-cost waste for the treatment of their waste waters.