Abstract:

In order to improve the separation efficiency of microbe exopolysaccharide(EPS) Wangia profunda SMA87 EPS (SMA87 EPS) from aqueous solution, the preparation of immobilized SMA87 EPS was optimized by orthogonal array design experiments. The four main factors were concentration of the polyvinylalcohol (PVA), sodium alginate (SA), EPS, and the hardening time. The major relevant indicator was Pb(II) removal rate, while three subordinate indicators were the spherical shape, extraction rate of the polysaccharide and acid resistance of the immobilized EPS grains. The results showed that the optimal ratio  of immobilized SMA87 EPS was obtained as m(PVA)∶m(SA)∶m(EPS)∶m(H2O)=80∶20∶1∶1000, and the hardening time was 16 h. Effects of immobilized EPS beads dosage, pH, and adsorption time were studied by batch experiments. The results showed that the removal rate increased with the immobilized EPS beads dosage increasing. The adsorption of Pb(II) onto the immobilized beads depended on the  pH value. The adsorption rate of the immersed beads was faster than that of the dry beads. The thermodynamic isotherm of Pb(II) adsorption on immobilized EPS beads could be best  described by the Langmuir model, with a regression coefficient of 0.954 and a  theoretical maximum adsorption capacity of 82.64mg／g. The pseudo-second-order model well fitted the kinetic process of Pb(II)  adsorption by immobilized EPS beads, and the adsorption process was controlled by more than two steps.

Key words:  orthogonal array design experiment, exopolysaccharide immobilization, Pb(II) adsorption