Electrochemical recovery of low concentration of palladium from palladium(II) chloride of electroplating wastewater

Abstract

BACKGROUND: An electrochemical recovery of low concentration of palladium from a diluted palladium(II) chloride electroplating wastewater is presented. The electrochemical method used was an electrogenerative system which operated with a batch reactor.RESULTS: A three-dimensional cathode material of reticulated vitreous carbon (RVC) appeared to give the reactor less polarization compared to a three-dimensional porous graphite and two-dimensional stainless steel. Mass transport study confirmed RVC as the most suitable cathode in this electrogenerative system. The generated flow current of this system was supported by high performance of zinc as anode, compared to aluminium. Sulfuric acid served as the best cathode activation solution, having the highest recovery rate, with >90% of palladium being recovered in 5 h. Low concentrations of palladium(II) chloride solutions (100-500 mg L −1 ) were recovered at pH 5. Scanning electron microscopy-energy-dispersive X-ray spectroscopy was used for qualitative and quantitative analysis of deposited palladium on the cathode. It was shown that a pure metallic palladium deposits from chloride solution were obtained. Finally, the developed electrochemical reactor was also used to recover palladium from diluted electroplating wastewaters, and the results were satisfactory (>90% recovery).CONCLUSION: This research shows that the electrogenerative system has the potential to recover palladium from diluted electroplating wastewaters.

Electrochemical Metal Recycling: Recovery of Palladium from Solution and In Situ Fabrication of Palladium-Carbon Catalysts via Impact Electrochemistry

“…65 Other sources of soluble palladium (often PdCl 2 ) such as e-waste (electroplating and printed circuit boards) can result in concentrations of 1500 mg L −1 in waste streams. 66 Concentrations in natural waters are significantly lower, with Pd concentrations of 22 ng L −1 and 70 pg L −1 being detected in fresh water and sea water, respectively. 67 Palladium metal has historically been considered relatively low in toxicity; however, its compounds such as palladium (II) wildlife even in minute amounts.…”

“…Pd-modified carbon nanostructured catalysts are extensively used in a range of applications: from electrochemical sensors and organic synthesis to the oxidation of formic acid and reduction of oxygen in fuel cells. − However, the use of Pd can lead to environmental pollution via release of contaminated waste solutions and particles. − For example, the World Health Organization has reported concentrations of 260 μg kg –1 in sewage sludge and up to 4.7 mg kg –1 in waste discharged from the jewelry industries . Other sources of soluble palladium (often PdCl 2 ) such as e-waste (electroplating and printed circuit boards) can result in concentrations of 1500 mg L –1 in waste streams . Concentrations in natural waters are significantly lower, with Pd concentrations of 22 ng L –1 and 70 pg L –1 being detected in fresh water and sea water, respectively .…”

“…The primary method used to recover spent Pd catalysts is hydrometallurgy which is limited because of the significant volumes of toxic and expensive reagents needed and the further production of hazardous waste such as nitric oxides. ,− These methods, often requiring the pretreatment of Pd, have been able to achieve recovery within the range of 58–97% − but are considered ineffective for the removal of metals from waste solutions at low concentrations resulting in waste storage challenges and reduced profit. ,, Therefore, more environmentally sustainable methods of Pd nanoparticle synthesis and recovery have been investigated. ,,, Electrodeposition is considered a practical method for metal recovery because of its operational feasibility, with the deposition controlled through the potential applied and metal ion concentration, − and traditional electrodeposition methods have many industrial applications. − The use of electrochemical systems such as galvanic reduction and recovery from ionic liquids after solvent extraction have been explored within the literature as a method of Pd extraction achieving a recovery of 90–99%. , Higher recoveries were observed in systems increasing mass transport via the use of rotating electrodes or flow of the plating solution. , However, overall recovery or recycling efficiency is not necessarily easily compared because studies often focus on one part of the recycling process (usually recovery, rather than separation, dissolution, etc. ).…”

“…4,72−74 These methods, often requiring the pretreatment of Pd, have been able to achieve recovery within the range of 58−97% 75−83 but are considered ineffective for the removal of metals from waste solutions at low concentrations resulting in waste storage challenges and reduced profit. 66,84,85 Therefore, more environmentally sustainable methods of Pd nanoparticle synthesis and recovery have been investigated. 37,66,86,87 Electrodeposition is considered a practical method for metal recovery because of its operational feasibility, with the deposition controlled through the potential applied and metal ion concentration, 88−91 and traditional electrodeposition methods have many industrial applications.…”

“…66,84,85 Therefore, more environmentally sustainable methods of Pd nanoparticle synthesis and recovery have been investigated. 37,66,86,87 Electrodeposition is considered a practical method for metal recovery because of its operational feasibility, with the deposition controlled through the potential applied and metal ion concentration, 88−91 and traditional electrodeposition methods have many industrial applications. 92−98 The use of electrochemical systems such as galvanic reduction and recovery from ionic liquids after solvent extraction have been explored within the literature as a method of Pd extraction achieving a recovery of 90−99%.…”