Poly(hydroxiethyl methacrylate) resins as supports for copper (II) biosorption with Arthrobacter sp.: matrix nanomorphology and sorption performances

Arthrobacter sp. was entrapped inside a macro- and microporous matrix build up with poly(hydroxiethyl methacrylate) (Poly-HEMA) cross-linked with trimethylolpropanetrime-thacrylate (TMPTM). The resin-biomass complex (RBC) was prepared with different characteristics according to a factorial experiment. Factors investigated were: crosslinker (TMPTM) molar fraction, biomass concentration in the solid and particles granulometry. The nanomorphology and molecular accessibility of resins with different cross-linker concentrations have been studied with ISEC (Inverse Steric Exclusion Chromatography). Results indicated an essentially monodispersed structure of resins, with lower crosslinker weight fractions and a bidispersed structure of the resin with the highest cross-linking degree. Copper biosorption performances were examined with an analysis of variance (ANOVA), considering the specific uptake at equilibrium and the delay time as responses of the process. The analysis evidenced: (i) a negative effect (significance 97%) of biomass concentration on the maximum specific uptake; (ii) a positive effect (98%) of biomass concentration on the delay time; (iii) a positive effect (99.9%) of granulometry on the delay time; and (iv) a negative effect (99.1%) of the interaction between cross-linker and biomass concentration on the delay time. A maximum copper specific uptake of about 0.6 mg Cu g(-1) RBC (7 mg Cu g(-1) biomass d.w.) has been observed, in the case of a RBC with the following characteristics: 2% w cross-linker concentration, 8% w biomass concentration, 425-750 mu m granulometry.