Metal adsorption in aqueous media using Moringa oleifera Lam. seeds produced in Ecuador as an alternative method for water treatment

Abstract

This work explores the technical viability in the use ofMoringa oleifera Lam. seeds produced in Ecuador as an adsorbent medium for copper (Cu), nickel (Ni) and chromium (Cr) present in water that could be implemented in future Water Resource Recovery Facilities in Ecuador. The seeds were prepared following a sequence of washing, drying, crushing, sieving, rewashing, and final drying. Two treatments were performed based on particle size.  Treatment 1 consisted on a mixture of 70% of particles larger than 2 mm and 30% of particles between 1 and 2 mm; while Treatment 2 consisted only on 1 - 2 mm particles. Batch experiments were performed with metal concentrations ranging from 10 to 150 ppm, a dose of 1.00 g of MO per liter, and mechanical stirring for 1 hour. Treatment 2 showed to be more favorable to metal removal and the Langmuir model better characterized adsorption of the three metals.The best kinetic description of the three metals is that of a pseudo first-order reaction where the adsorption capacities are 50.93 mg Cu/g MO, 30.14 mg Ni/g MO, and 40.98 mg Cr/g MO, with removal percentage of 37 - 53 %, 39 - 76%, and 11 - 33%, respectively.