Submitted to: American Institute of Chemical Engineers Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: November 5, 1999
Publication Date: N/A
Technical Abstract: The textile industry generates a tremendous volume of wastewater requiring treatment. Cellulose- and lignocellulosic-based anion exchangers are very effective adsorbents for most commercially employed dyes. Conventional salts, acids, and bases are ineffective regenerants because of the strong affinity of dye for cationic (ligno)cellulosic exchangers, which makes adsorbent reuse uneconomical. This presentation describes the use of chemical and microbial redox systems to reductively cleave dye azo bonds while the dye is adsorbed to quaternized cellulose, leading to the ready regeneration of the adsorbent. For chemical reduction of azo dyes, the redox borohydride/bisulfite couple proved to be quite rapid and effective. With dye in solution or bound to resin only stoichiometric amounts of reductant were required to fully cleave all azo bonds. Subsequent salt or base treatment of the resin resulted in a high degree of regeneration of dye-binding capacity. Microbial regeneration of dye-saturated resin was investigated using a culture of Burkholderia cepacia (NRRL B-14803). Under anaerobic conditions and in the presence of the redox mediator, azo dye reduction occurred. It was demonstrated with various reactor designs that direct contact of the resin with bacteria is not necessary for dye reduction. The redox mediator acts as an electron shuttle between bacteria and resin held in separate containers. The microbial regeneration system provides a closed-loop process for the decolorization of textile wastewaters.