New treatment of real electroplating wastewater containing heavy metal ions by adsorption onto olive stone

The goal of this research was to develop new processes for the remediation of electroplating wastewater using olive stone as adsorbent material packed in fixed-bed columns. The study was performed with effluents containing chromium (VI), copper (II) and nickel (II) of an electroplating plant. First, we started our research from studying olive stone as an efficient biomaterial capable of removing chromium (VI) of both synthetic and real wastewater. The removal of chromium (VI) took place following two parallel mechanisms: the adsorption of chromium (VI) and the reduction of chromium (VI) to chromium (III) by contact with the biomass, appearing chromium (III) in the aqueous solution. Then, two fixed-bed columns were utilized for removal both chromium (VI) and chromium (III), in the first fixed-bed column, chromium (VI) was successfully removed and in the second column, the chromium (III). Finally, two types of adsorption experiments were selected for simultaneous adsorption of three metals: (1) with a first stage reduction of chromium and only one adsorption fixed-bed column; and (2) without the stage of reduction and two adsorption fixed-bed columns. The results showed that the second method was more suitable for the purposes of wastewater treatment. In the first column, chromium (VI) was completely removed. In the second column, the outlet concentration of heavy metals was 2.04, 1.48 and 0.93 mg/L for total chromium, copper (II), and nickel (II), respectively. This research provides a high efficient new alternative to clean industrial wastewater. •Olive stone was studied as an efficient biomaterial capable of removing Cr (VI) of wastewater.•Reliable evidences about the removal mechanism of Cr (VI) by olive stone were presented.•A combined effect of sorption and reduction is involved in the Cr (VI) removal.•A new process for treatment of electroplating industry wastewater is proposed.