Treatment of industrial electroplating wastewater for metals removal via electrocoagulation continous flow reactors

A real industrial electroplating rinsing wastewater was collected and subjected the physical and chemical examination. The study showed that it can be categorized as high strength wastewater, at pH- 2, COD 1430 mg/l, and high level of metals above permissible limits namely: 150, 30, 25, and 2.9 for Ni, Cu, Zn, and Fe mg/l respectively. Therefore, metals must be adequately removed before discharging to avoid any hazardous impact on the environment. Similar synthetic wastewater was prepared to study effect of chemical coagulation for the precipitation of metals. The optimum removal rate was achieved by using a combination of lime and ferric chloride at 100 and 30 mg/l respectively. The chemically treated electroplating wastewater was subjected to an electrocoagulation study. A comparison between iron and stainless-steel electrodes for the removal of metals was investigated. Furthermore, the effect of different electric voltage, and the contact time on metals removal efficiency were also examined. It was found that the optimum removal capacity was achieved when stainless steel electrode was employed in the presence of ferric chloride as coagulant, at 10 volts, 30 min. contact time, and pH 9 for synthetic solution. In a batch treatment system, the real industrial wastewater was treated at the predetermined optimum operating conditions; the removal of metals was 92.1%, 87.8% and 82.9% for Ni. Zn, and Cu respectively. By employing a continuous flow reactor for the treatment of the same real wastewater and under the same operating conditions; metals removal rate increased to 98.9%, 97.4% and 96.6% for Ni. Zn, and Cu respectively. The level of metals in the final treated wastewater copes with Egyptian Environmental Regulation. The overall results confirmed that the electro-coagulation (EC) technology offers an effective alternative process in combination with the conventional chemical coagulation process for reaching high removal performance of toxic metals from the electroplating wastewater. The advantage of EC technique is achieving high treatment efficiency instead of expensive chemical reagents, high construction cost and/or other conventional processes. In addition, the final treated water can be reused for rinsing process in electroplating industry and/or discharging without any environmental hazard effect. It is also recommended to employ solar energy instead of electricity to reduce cost of operation.

Recovering Zinc from electroplating wastewater by crystallization in a pellet reactor

A pellet reactor (PR) was used to investigate the ability for zinc recovery from electroplating wastewater. The pellet reactor is a fluidized bed reactor, in which the nucleated precipitation of heavy metals occurred on the surface of seeding material. The zinc removal efficiency was 75% at molar ratio [CO3 2-]/[Zn2+] of 2.5, the flowrate of 16 L/h, sand’s diameter of 0.25 – 0.5 mm, and sand’s mass of 50 g. The elemental analysis of zinc carbonate and zinc hydroxide crystallization was analyzed by X-ray energy dispersive spectrometer (EDS) and the surface was characterised by Scanning electron microscope (SEM) to get the morphological observation of the pellets after 38-day operation. This study demonstrated that the fluidized bed reactor can be considered a feasible method for zinc removal efficiency from electroplating wastewater to achieve sustainable development.

Reclamation of Cobalt and Copper from Single- and Co-contaminated Wastewater via Carbonate and Hydroxide Precipitation

Wastewater containing cobalt and copper comprised of plating wash water, plant wash water, and equipment cooling and wash water is generated in the electroplating industry. These metals can be detrimental to humans, animals, plants, and the environment. Thus, it is necessary to treat electroplating wastewater to remove these toxic metals. Carbonate and hydroxide precipitation were utilized for the removal of Co(II) and Cu(II) from synthetic electroplating wastewater by jar tests in this work. The effects of solution pH, precipitant-to-metal ratio, and type of precipitant on the precipitation efficiency of cobalt and copper from the single- and co-contaminated systems were investigated. Carbonate precipitation achieved higher removal efficiency for both target metals in the single- and co-contaminated wastewater streams. Furthermore, it can operate at relatively low pH range of about 7.0-8.0. Cobalt in both pollutant systems was almost completely removed at pH 10.0 using both precipitant systems. Copper was found to be easily removed which was possibly brought about by precipitation-adsorption mechanism. The extent of the co-removal of cobalt with copper is significantly pH dependent. The effect of precipitant-to-metal ratio for cobalt and copper treatment varied in single- and co-contaminated streams. Carbonate precipitation led to lower sludge density than that of hydroxide precipitation.