Journal of Hazardous Materials B124 (2005) 230–235 Recovery of H 2 SO 4 from waste acid solution by a diffusion dialysis method Jinki Jeong, Min-Seuk Kim, Byung-Su Kim, Soo-Kyung Kim, Won-Baek Kim, Jae-Chun Lee ∗ Minerals and Materials Processing Division, Korea Institute of Geoscience and Mineral Resources, 30 Gajeong-dong, Yuseong-gu, Daejeon 305-350, Republic of Korea Received 16 February 2005; received in revised form 13 May 2005; accepted 13 May 2005 Available online 16 June 2005 Abstract A diffusion dialysis method using anion exchange membrane was used to recover H 2 SO 4 from waste sulfuric acid solution produced at the diamond manufacturing process. Effects of flow rate, operation temperature, and metal ion concentration on the recovery of H 2 SO 4 were investigated. The recovery of H 2 SO 4 increased with the concentration of H 2 SO 4 and operation temperature. It also increased with the flow rate ratio of water/H 2 SO 4 solution up to 1, above which no further increase was observed. The flow rate did not affect the rejection of Fe and Ni ions. About 80% of H 2 SO 4 could be recovered from waste sulfuric acid which contained 4.5 M free-H 2 SO 4 at the flow rate of 0.26 × 10 -3 m 3 /h m 3 . The concentration of recovered H 2 SO 4 was 4.3 M and the total impurity was 2000 ppm. Preliminary economic evaluation has revealed that the dialysis system is highly attractive one that has payback period of only few months. © 2005 Elsevier B.V. All rights reserved. Keywords: Sulfuric acid recovery; Diffusion dialysis; Waste; Fe; Ni 1. Introduction Sulfuric acid (H 2 SO 4 ) solution has been widely used in chemical and metal industries for various surface treatments as electrolysis, electroplating, and acid pickling because of its relative inexpensiveness compared with other acids [1,2]. As a result, large amounts of waste sulfuric acid solution have been generated causing environmental problems. The waste sulfuric acid solution contains valuable metals as Fe, Ni, and Co and so on. It is thus required to develop an alternative method to recover sulfuric acid and valuable metals, simul- taneously. The waste sulfuric acid solution can be treated by various methods as cooling, evaporation, distillation, thermal decomposition, solvent extraction and membrane ∗ Corresponding author. Fax: +82 42 861 9727. E-mail address: jclee@kigam.re.kr (J.-C. Lee). separation [3–6]. Among them, the membrane separation methods have been favored due to its lower energy con- sumption and the cleaner nature. One of the membrane separation methods is a diffusion dialysis (DD) using membrane. The technology has been commercialized in aluminum anodizing process, pickling of secondary steel products, aluminum foil etching process and etching of stainless steel. In the diffusion dialysis method using membrane, there are many advantages such as low energy consumption, simple plant, continuity operation, stable and easy operation, low installation cost, and low operating cost. In this study, a diffusion dialysis method using anion exchange membrane was suggested for recovering H 2 SO 4 from waste sulfuric acid solution containing metal ions which was generated from diamond manufacturing plants. The effects of H 2 SO 4 concentration, flow rate, temperature, and metal ion concentration on the recovery of H 2 SO 4 were inves- tigated using a continuous contactor. 0304-3894/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.jhazmat.2005.05.005