Studium biosorpce Cr(VI) z průmyslových odpadních vod pomocí Acidithiobacillus ferrooxidans a Acetobacter aceti.

Abstract

There have been a number of studies considering the possibility of removing and recovering heavy metals from diluted solutions. These are due, principally, because of the commercial value of some metals as well as in the environmental impact caused by them. The traditional methods for removing have several disadvantages, especially when metals are present in concentrations lower than 100 mg l-1. Biosorption, which uses biological materials as adsorbents, has been considered as an alternative method. In this dissertation work, two different species of bacterial biomass were used as biosorbents to remove Cr(VI) from aqueous solutions. Batch experiments were conducted to study the effects of temperature (20 °C and 40 °C), initial concentration of biosorbent (0,2 mg l−1 and 0,8 mg l−1), pH of solution (1 and 5 for Acidithiobacillus ferrooxidans, resp. 2 and 6 for Acetobacter aceti) and agitation speed (200 ot min-1 and 400 ot min-1) on biosorption. Due to their acidophilic nature, bacterial biomass was able to adsorb Cr(VI) at a very high level. The 24 factorial design was used to optimalize the parameters of biosorption. The main effect on the biosorption process had a pH value. The removal rate of Cr(VI) was enhanced by very acid conditions. The kinetics of the adsorption was discussed on the basis of two kinetic models, i. e., the pseudo-first-order and the pseudo-second-order. Equilibrium was reached after 80 min for Acidithiobacillus ferrrooxidans, respectively 100 min for Acetobacter aceti. The pseudo-second-order kinetic model described the adsorption of Cr(VI) on bacterial biomass better then pseudo-first-order kinetic model. The non-linear Langmuir model provided the best correlation of experimental data, maximum adsorption capacity of Cr(VI) was 1 458,3 mg g-1 for Acidithiobacillus ferrooxidans and 2 994,3 mg g−1 for Acetobacter aceti. These results demonstrated the suitability of using Acetobacter aceti biomass. The removal efficiency of Cr(VI) from real industrial wastewater from arms production of company Česká zbrojovka a.s., Uherský Brod reached 82,5 %. Biomass Acidithiobacillus ferrooxidans has demonstrated half efficiency in comparison with biomass Acetobacter aceti and therefore was evaluated to be unsuitable for the removal of Cr(VI).