Papers by Keyword: Electrodeionization

Abstract: Electrodeionization (EDI) is being applied more and more to treat wastewater containing heavy metal ions, especially for electroplating rinsing wastewater. The effects of feed water conditions including concentration, pH and temperature on the performance of EDI process for removal of Ni2+ from dilute synthetic wastewater were investigated systematically in this paper. It was found that the dilute resistivity of the EDI module descended from 1.5-2.8MΩ•cm to 0.36-0.45MΩ•cm while the influent Ni2+ concentration increased from 45 mg•L^-1 to 63mg•L^-1. Existence of some H+ in feed water would push the stack current up. An increase in temperature of feed water would facilitate the ion exchange and diffusion and thus promote mass transfer. It was indicated that feed water conditions had a significant effect on separation performance of EDI process for treating dilute solutions containing heavy metal ions. Pure water production could be accomplished and water reuse could be realized via EDI technology by appropriately restricting feed water conditions.

Abstract: The purpose of this study was to investigate the influence of packing form on the performance of electrodeionization (EDI) process for removal Ni2+ from synthetic wastewater. With feed water containing about 50mg•L^-1 Ni²⁺ at pH of 5.7, the dilute resistivity of the product stream with mixed bed and layered bed were in the range of 1.41-1.72MΩ•cm and 1.08-1.27MΩ•cm, respectively. The precipitation of metal hydroxide could be reduced effectively by using layered bed. With optimum operating conditions, the wastewater containing Ni2+ could be purified and be reused by EDI process.

Abstract: Electrodeionization(EDI) is an electro-membrane process with high efficiency for deep desalinating, where water dissociation mechanism occurring on the surface of ion exchange membranes and resins typically exsits and acts. But when used to treat heavy metal-containing solutions such as effluents from the electronic industry, the EDI will suffer from metal-hydroxides precipitation which would destroy the separation process irreversible. With the primary aim to solve that problem, an electrodeionization process coupled with bipolar membrane (BMEDI) was developed together with a preacidification method. The effects of separating and concentrating heavy metal ions by the BMEDI were studied with NiSO₄ solution containing 24 mg×L^-1 Ni²⁺ ions. The results suggested that, the nickel-concentration in the dilute products were both below the analysis limit at constant current densities of 40 mA·cm^-2 and 10 mA·cm^-2, while a concentration factor of 31 was achieved at 40 mA·cm^-2. In addition, no Ni(OH)₂ precipitation was found in all the compartments throughout the experiments, which provide a guarantee of good stability for long-time operation.

Abstract: Applicable configuration alteration of the electrodeionization （EDI）process commonly for pure water production was carried out to treat dilute nickel wastewater in this paper. The effects of major operating parameters such as applied voltage, dilute and concentrate stream flow rates on the performance of EDI process were investigated systematically. The results showed that, with the feed water containing 50mg·L^-1 Ni²⁺ and pH of 5.7, the dilute resistivity of the EDI could reach higher than 1.0MΩ·cm which gave a Ni²⁺ rejection more than 99.8% while the Ni²⁺ was concentrated as high as 1564mg·L^-1 in the concentrate stream by optimizing the operating parameters. It was indicated that pure water production and concentrating of heavy metal ions could be simultaneously accomplished via EDI technology just in one process, valuable heavy metal and water resource could be recovered as well.

Abstract: The aim of the present work was to study the effect of properties of ion exchange membrane on separation performance of electrodeionization (EDI) process for removal of nickel ions from dilute heavy metal solutions. It was shown that the properties of ion exchange membrane had a significant effect on removal of nickel ions. With feed water containing nickel ions at the concentration of 55mg•L^-1, the nickel ions concentration of dilute stream was lower than 0.5mg•L^-1 and the nickel rejection was greater than 99% when using EDI membranes, while that was in the range of 2.48-3.55mg•L^-1 with conventional heterogeneous ion exchange membranes. With optimum ion exchange material and operating conditions, EDI would be a very interesting and innovative technology for the treatment of dilute heavy metal solutions.