Hydrophobic Modification Of Konjac Glucomannan As An Adsorbent And Its Applied Basic Research

The research was supported by the project of the Key Technology R&D Program of China. The project is the preparation and study of bioadsorbent for mining wastewater (No.2007BAB 18808). Konjac glucomannan (KGM), which was rich and renewable in China as a raw material, was used to synthesize novel functional konjac glucomannan through hydrophobic and thermoplastic modification. The functional konjac glucomannan was used to treat organic or inorganic wastewater.The results were concluded as follows:(1) Hydrophobic deacetylated KGM was prepared by inverse suspension controlled deacetylation method. The results showed that the water absorbency of KGM was controlled by the amount of residue acetyl groups. When the amount of acetyl groups was decreased from 1.85% to 0%, the water absorbency of KGM was relevantly decreased from 100 g H2O/g KGM to 5 g H2O/g KGM.(2) Advanced rotational rheometer was used to study how the residue acetyl group on KGM influenced its rheological properties and viscoelasticity. The results indicated that KGM sol of the amount of acetyl group lower than 1.05% easily sheared thinning, slightly decreased of the linear viscoelastic, and showed thixotropy. Creep recovery test results showed that the elasticity of KGM Sol enhanced as the amount of residue acetyl group on KGM was decreased.(3) Deacetylated konjac glucomannan (DKGM) was used as an adsorbent to treat tannin wastewater. DKGM has strong affinity to adsorb tannin with maximum adsorption capacity of 1.5 g tannin/g DKGM at high tannin concentration. The maximum removal efficiency was about 90%. It was also found that the adsorption behavior is much dependent on the effect of pH. The optimum pH range was from 2 to 6. The adsorption mechanism of tannin onto DKGM is multiple-layer hydrogen bonding adsorption process. DKGM has good potential to recycle tannin from wastewater.(4) Thermoplastic deacetylated konjac glucomannan absorbent (TDKGM) was synthesized by free radical graft copolymerization of methyl acrylate (MA) and methylmethacrylate (MMA) onto the backbone of deacetylated konjac glucomannan. TDKGM can be easily separated and purified from the mixed system. The glass temperature of TDKGM can be controlled from 14.8℃to 123.4℃through adjusting the mass ratio of MA and MMA. Thermoplastic processing properties of TDKGM was related to its grafting efficiency. When the grafting efficiency is much than 200%, TDKGM can be easily processed as well as HDPE. TDKGM adsorbent with regular shape and good mechanical properties can be easily prepared by single-screw extruder, which solves the problem that traditional bioadsorbent can not easily processed in industrial scale.(5) Activated TDKGM is a weak acid-type adsorbent with ion exchange capacity of 1mmol/g, and it can be used to treat heavy metals wastewater. Activated TDKGM has good affinity to adsorb Cu2+ or Pb2+ ion from low concerntration wastewater with removal efficiency of more than 98%. Activated TDKGM can be easily regenerated by HCl.