Producing protein intercalated bentonite - Equilibrium, kinetics and physical properties of gelatin-bentonite system

摘要

Protein intercalated bentonite was produced using gelatin with calcium (CaBt), sodium (NaBt) and octadecylamine-modified bentonite (amine Bt). Adsorption isotherms and rates were investigated from pH 3 to pH 9 and 4 to 20 mg/ml initial gelatin concentrations using 3 g of adsorbent loading per 100 ml solution. At 20 mg/ml gelatin solution, the highest gelatin adsorption obtained for CaBt was 372 mg/g or 58.9% gelatin recovery between pH 3 to pH 5.23 while NaBt showed the best adsorption between pH 7 to pH 9 with 405 mg/g or 60.4% gelatin recovery. Amine Bt showed consistently poor adsorption with the highest gelatin adsorption of 222 mg/g or 33.5% recovery at pH 3. Basal spacing (d-value) for CaBt increased from 16.3 to 20 A while NaBt increased from 12.4 to 20-23 A., indicating that intercalation had occurred. Adsorption equilibriums were modelled using the Langmuir, Freundlich, Langmuir-Freundlich and Temkin isotherms. The best regression coefficients were given by the Langmuir-Freundlich isotherm for CaBt and NaBt, and by the Freundlich isotherm for amine Bt. Adsorption was rapid with gelatin-bentonite solutions reaching equilibrium within 10-20 min. Adsorption rates decreased with increasing initial gelatin concentration suggesting that protein diffusion decreased due to increased solution viscosity.