Research On Treatment Of Heavy Metal Wastewater By Bacteria Using Electroanalytical Techniques

Recently, using microorganisms for recovery of heavy metals has received great attention. The development in this area has created a great demand on analytical chemistry .Piezoelectric bulk acoustic wave has been applied to numerous fields such as analytical chemistry, biochemistry, environmental monitoring, life science and molecular biology because of its advantages such as high sensitivity, broad sensing-spectrum, simple construction and low cost. The electrochemical techniques, especially stripping voltammetry, for the trace analysis of metal ions offer special advantage due to their high sensitivity, ease of application, low cost, high selectivity and accuracy. In this thesis, piezoelectric bulk acoustic wave and stripping voltammetry were used for investigating bioremediation of heavy metal ions. The creative works of this thesis are summarized as follows:1. A novel system combined acoustic wave impedance (AWI) analyzer with UV-vis spectrophotometer was developed for the study of chromium (VI) reduction kinetics by Pseudomonas aeruginosa (P. aeruginosa). AWI gave information about the growth of P. aeruginosa, and UV-vis spectrophotometer gave information about the concentration of chromium (VI) simultaneously. A combined system response model, for chromium (VI) reduction kinetics at lower initial chromium (VI) concentrations, was derived and proved based on the novel system. Taking into account the effect of bacterial growth on chromium (VI) reduction, the new model successfully simulated chromium (VI) bioremediation process. By fitting chromium (VI) reduction data toward the derived model, the kinetic parameters related to the process were obtained.2. We investigated chromium (VI) reduction kinetics by mixed culture of P. aeruginosa and E. coli. This study revealed the interactive correlations between P. aeruginosa and E. coli. P. aeruginosa was the dominant species in the mixed culture. The growth of E. coli was severely inhibited by the growth of P. aeruginosa. The kinetic process was also studied. The kinetic parameters of Cr(VI) reduction by mixed culture were obtained by the non-linear fitting.3. Linear sweep anodic stripping voltammetry (LSASV) at disorganized monolayer modified electrodes was first used to study the transient behavior of copper biosorption onto the biomass of P. aeruginosa. A porous disorganized monolayer was formed on the surface of the gold electrode by self-assembly of mercaptoethane sulfonate (MES), which could inhibit surface fouling by P. aeruginosa, while allowing movement of free copper ion through the layer for voltammetric detection at the underlying electrode. Based on the electrochemical results, the kinetics and equilibrium of biosorption were studied. The kinetic parameters and maximum adsorption capacity were obtained by the non-linear fitting.4. Semi-interpenetrating polymer network hydrogel based on polyacrylamide and chitosan was prepared to immobilize non-active P. aeruginosa. The immobilized P. aeruginosa beads were used to adsorb copper(II). The novel biosorbent showed good adsorption performance. The copper(II) biosorption was fast and equilibrium was attained within 40 min. It was found that the overall biosorption process was best described by pseudo-second-order kinetic model. Equilibrium data were well described by Langmuir adsorption isotherm.