Cd2+ and Cu2+ removal by the waste of the marine brown macroalga Hydroclathrus clathratus

The residue powder of brown macroalga Hydroclathrus clathratus (RH), after extracting most of its active components in 70% methanol, was used as adsorbent material for wastewater treatment from Cd2+ and Cu(2+ )metals ions. We investigated the metal adsorption isotherms and kinetics, the effect of initial metal ions concentration, contact time, adsorbent dosage, temperature and pH value. The reusability of RH waste on metal ions removal was also studied. The results showed that the removal% of metal ions generally increased with decreasing initial metal concentration. The adsorption % increased by increasing RH dosage till certain limit, then it decreased. The metal removal % slightly changes with the increase in the temperature for Cd2+ and it also increased at high temperature for Cu2+. The adsorption % was increased with increasing pH of the solution from 3 to 5 and decreases at pH=6.2, then it increased again at pH=8. Interestingly, RH waste was excellent reusable for Cu2+ but not preferred for Cd(2+ )removal from aqueous solution. The adsorption isotherm of Cd2+ and Cu2+ metals ions on RH almost agreed with Freundlich isotherm and pseudo-second-order kinetics for both metal ions. Where the maximum amounts of metals ions adsorbed were 96.46 and 43.4 mg/g for Cd2+ and Cu2+, respectively. (C) 2019 Elsevier B.V. All rights reserved.