Enzymatic grafting of carboxyl groups on to chitosan--to confer on chitosan the property of a cationic dye adsorbent.
Chitosan (CTS) is a good adsorbent for dyes but lacks the ability to adsorb cationic dyes. In this study, chitosan was modified to possess the ability to adsorb cationic dyes from water. Four kinds of phenol derivatives: 4-hydroxybenzoic acid (BA), 3,4-dihydroxybenzoic acid (DBA), 3,4-dihydroxyphenyl-acetic acid (PA), hydrocaffeic acid (CA) were used individually as substrates of tyrosinase to graft onto chitosan. FTIR analysis provided supporting evidence of phenol derivatives being grafted. The grafting amounts of these phenol derivatives onto chitosan were examined by the adsorption of an anionic dye (amaranth) and reached a plateau value. The final contents of carboxyl groups in chitosan (mmol carboxyl groups per kg chitosan) were measured as 46.36 for BA, 70.32 for DBA, 106.44 for PA, and 113.15 for CA. These modified chitosans were used in experiments on uptake of the cationic dyes crystal violet (CV) and bismarck brown Y (BB) by a batch adsorption technique at pH 7 for CV and at pH 9 for BB and 30 degrees C. Langmuir type adsorption was found, and the maximum adsorption capacities for both dyes were increased with the following order CTS-CA>CTS-PA>CTS-DBA>CTS-BA.
Laboratory of Polymer materials Research, Department of Chemical and materials Engineering, National Central University, Chung-Li 320, ROC Taiwan.
An-Chong
AC
Chao
Shin-Shing
SS
Shyu
Yu-Chuang
YC
Lin
Fwu-Long
FL
Mi
D000327:Adsorption; D001391:Azo Compounds; D002245:Carbon Dioxide / Q000737:chemistry*; D002412:Cations; D002686:Chitin / Q000031:analogs & derivatives* / Q000737:chemistry*; D048271:Chitosan; D004396:Coloring Agents / Q000737:chemistry*; D004785:Environmental Pollutants; D005840:Gentian Violet; D014442:Monophenol Monooxygenase; D010636:Phenols; D014865:Waste Disposal, Fluid / Q000379:methods*; D018508:Water Purification / Q000379:methods*
D001391:Azo Compounds; D002412:Cations; D004396:Coloring Agents; D004785:Environmental Pollutants; D010636:Phenols; D002686:Chitin; D002245:Carbon Dioxide; C041069:carboxyl radical; C032806:Bismark Brown; D048271:Chitosan; D014442:Monophenol Monooxygenase; D005840:Gentian Violet