Journal of Hazardous Materials 145 (2007) 250–255 Adsorption of Reactive Red 141 from wastewater onto modified chitin Rujira Dolphen a , Niramol Sakkayawong a,1 , Paitip Thiravetyan a,∗ , Woranan Nakbanpote b a School of Bioresources and Technology, King Mongkut’s University of Technology Thonburi, 83 Moo. 8 Thakham, Bangkhuntien, Bangkok 10150, Thailand b Pilot Plant Development and Training Institute, King Mongkut’s University of Technology Thonburi, 83 Moo. 8 Thakham, Bangkhuntien, Bangkok 10150, Thailand Received 7 September 2006; received in revised form 9 November 2006; accepted 12 November 2006 Available online 19 November 2006 Abstract This research involved the adsorption of synthetic reactive dye wastewater (SRDW) by chitin modified by sodium hypochlorite and original chitin in batch experiments. The comparison of maximum adsorption capacity used the Langmuir model to describe SRDW adsorption onto chitin and modified chitin under a system pH of 11.0. Maximum dye adsorption by chitin increased from 133 mg g -1 to 167 mg g -1 at temperatures of 30–60 ◦ C, respectively. For modified chitin, the capacity decreased from 124 mg g -1 to 59 mg g -1 when the temperature increased from 30 ◦ C to 60 ◦ C, respectively. Both Na 2 SO 4 and Na 2 CO 3 increased in dye adsorption. The spectra of attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectrometry confirmed the hydroxyl groups as functional groups of modified chitin, which affected the modification and the SRDW adsorption. The adsorbed dyes were eluted by distilled water and 1M NaOH to confirm the dye adsorption mechanism. Total elution of modified chitin and chitin were 92.76% and 55.29%, respectively. Although modified chitin had a maximum adsorption capacity less than chitin, elution of the dye from modified chitin was easier than chitin. Therefore, modified chitin could be suitable in a column system for dye pre-concentration as well as wastewater minimisation. In addition, the column study showed that modified chitin could be used for more than four cycles of adsorption and elution by distilled water. © 2006 Elsevier B.V. All rights reserved. Keywords: Adsorption; Chitin; Reactive dye; Sodium hypochlorite; ATR-FTIR 1. Introduction The wastewater produced by textile industries is currently an important problem in Thailand. These industries produce a lot of wastewater, which includes a large number of contaminants such as acids, caustics, toxic organics, inorganics, dissolved solids, and dyes [1,2]. Among textile effluents, reactive dye wastewater has limited biodegradability in an aerobic environ- ment, while many azo dyes, constituting the largest dye groups, may, under anaerobic conditions in the environment, decompose into potential carcinogenic aromatic amines [3,4]. Furthermore, it is difficult to remove reactive dyes using chemical coagula- tion due to the dyes’ high solubility in water [5]. Adsorption with activated carbon appears to be the best prospect for elim- ∗ Corresponding author. Tel.: +66 2 470 7535; fax: +66 2 452 3455. E-mail address: paitip.thi@kmutt.ac.th (P. Thiravetyan). 1 Present address: Division of Biotechnology, Thammasat University, Bangkok, Thailand. ination of this dye. Despite its effectiveness, this adsorbent is expensive and difficult to regenerate after use. Therefore, many researches in recent years have focused on the use of various low-cost adsorbents to replace activated carbon [6]. Chitin is usually obtained from waste materials from the seafood processing industry, mainly shells of crab, shrimp, prawn and krill [7]. Shrimp shell waste is a plentiful waste from the Thai seafood processing industries (200,000 t per year). This polymer is also known to be an effective adsorbent in the adsorp- tion of reactive dyes [8–11]. Accordingly, chitin has the potential to be an inexpensive and effective adsorbent for reactive dye wastewater removal, but the problem with chitin is the difficulty in the elution of adsorbed-dye adsorbent, making this adsorbent suitable for only one time use. Therefore, modified chitin is pre- treated by sodium hypochlorite solution, which allows elution easily by water. Therefore, modified chitin was selected as the adsorbent in this study. The objective of this research is to study the feasibility of using modified chitin as a new adsorbent for the removal of azo reactive dye from SRDW. The SRDW, which contains C.I. 0304-3894/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jhazmat.2006.11.026