Dursun Özer

Comparative study of the biosorption of Pb(II), Ni(II) and Cr(VI) ions onto S. cerevisiae: determination of biosorption heats

In this study, the biosorption of Pb(II), Ni(II) and Cr(VI) ions onto inactive Saccharomyces cerevisiae was investigated as a function of initial pH, initial metal ion concentration and temperature. The Langmuir model was applied to experimental equilibrium data of Pb(II), Ni(II) and Cr(VI) biosorption depending on temperature and the maximum metal ions uptake at optimum biosorption temperature of 25 degrees C, were found to be 270.3, 46.3 and 32.6 mgg(-1), respectively. Using the Langmuir constant, b values obtained at different temperatures, the biosorption heats of Pb(II), Ni(II) and Cr(VI) were determined as -1.125, -1.912 and -2.89 kcalmol(-1), respectively. The results indicated that the biosorption of Pb(II), Ni(II) and Cr(VI) ions to S. cerevisiae is by the physical adsorption and has an exothermic nature.

A comparative study of various biosorbents for removal of chromium(VI) ions from industrial waste waters

Abstract Chromium(VI) biosorption to non-living biomass of Chlorella vulgaris, Clodophara crispata, Zoogloea ramigera, Rhizopus arrhizus and Saccharomyces cerevisiae was investigated. The initial pH of the metal ion solution effected metal uptake capacity of the biomass and the optimum initial pH was found as 1·–2·0 for all microorganisms. Maximum adsorption rates of metal ions to microbial biomass were obtained at temperatures in the range 25–35°C. The adsorption rate increased with increasing metal ion concentration for C. vulgaris, C. crispata, R. Arrhizus, S. cerevisiae and Z. ramigera up to 200, 200, 125, 100 and 75 mg/litre, respectively. Freundlich constants were determined from the Freundlich adsorption isotherms of all microorganisms.

Influence of oxygen transfer on lipase production by Rhizopus arrhizus

Abstract The effect of oxygen on lipase production by Rhizopus arrhizus was studied under two operating modes, controlled dissolved oxygen concentration (DO) and controlled aeration rate. Lipase production depended more extensively on oxygen than cell growth. The intrinsic factor determining cell growth and lipase production was oxygen transfer rate (OTR) rather than DO concentration. Improvements in OTR, either by aeration or agitation or perfluorocarbon (PFC) inclusion resulted in an increase in lipase production. The formation of lipase could be described by a mixed-growth associated model. The overall productivity for the lipase which depended more strongly on agitation than aeration could be related to the volumetric oxygen transfer coefficient, k L a. Addition of 10% (v/v) PFC to the fermentation medium also resulted in higher lipase production.

A comparative study of the biosorption of lead(II) ions to Z. ramigera and R. arrhizus

Parameters that affected adsorption rates of lead(II) ions on Z. ramigera and R. arrhizus were investigated. The adsorption rates and equilibrium metal removal were strongly affected by pH, temperature, and initial metal concentration. Both micro-organisms exhibited the highest lead-adsorptive rate at pH 4.5–5.0. Maximum adsorption rates of metal ions to Z. ramigera and R. arrhizus were obtained at temperatures ranging from 25 to 45°C. The initial adsorption rate of metal ion increased with increasing metal ion concentration for Z. ramigera and R. arrhizus up to 150–200 mg litre−1 and 200–300 mg litre−1, respectively. Isotherms for the adsorption of lead on Z. ramigera and R. arrhizus were developed and Freundlich constants determined from the Freundlich adsorption isotherms.

Response surface analysis of lipase production by freely suspended Rhizopus arrhizus

Abstract The combined effects of initial glucose concentration and inducer (corn oil) concentration on lipase production by freely suspended Rhizopus arrhizus were investigated using response surface methodology (RSM). A 2 2 full-factorial central composite design was employed for experimental design and analysis of the results. The optimum glucose and inducer concentrations were found to be 1.1 and 3.3 g/l, respectively. In these conditions, the biomass concentration of 2.4 g/l with a lipolytic activity of 370 μmol/l min was attained. These results are in close agreement with the model parameters.

APPLICATION OF FREUNDLICH AND LANGMUIR MODELS TO MULTISTAGE PURIFICATION PROCESS TO REMOVE HEAVY METAL IONS BY USING SCHIZOMERIS LEIBLEINII

The adsorption of iron(III), lead(II) and cadmium(II) ions onto Schizomeris leibleinii, a green alga, was studied with respect to initial pH, temperature, initial metal ion and biomass concentration to determine the optimum adsorption conditions. Optimum initial pH for iron(III), lead(II) and cadmium(II) ions were 2.5, 4.5 and 5.0 at optimum temperature 30°C, respectively. The initial adsorption rates increased with increasing initial iron(III), lead(II) and cadmium(II) ion concentrations up to 100, 100 and 150 mg l−1, respectively. The Freundlich and Langmuir adsorption isotherms were developed at various initial pH and temperature values. The adsorption of these metal ions to S. leibleinii was investigated in a two-stage mixed batch reactor. The residual metal ion concentrations (Ceq) at equilibrium at each stage for a given ‘quantity of dried algae (X0)/volume of solution containing heavy metal ion (V0)’ ratio were calculated using Freundlich and Langmuir isotherm constants. The experimental biosorption equilibrium data for iron(III), lead(II) and cadmium(II) ions were in good agreement with those calculated by both Freundlich and Langmuir models. The adsorbed iron(III), lead(II) and cadmium(II) ion concentrations increased with increasing X0/V0 ratios while the adsorbed metal quantities per unit mass of dried algae decreased.

Adsorption isotherms of lead(II) and chromium(VI) on Cladophora crispata

Abstract The biosorption of heavy metal ions by algae is a promising property with a potential for industrial use. The adsorption of lead(II) and chromium(VI) ions on Cladophora crispata, a green algae, was studied with respect to adsorption pH and temperature in order to determine the optimum conditions for lead(II) and chromium(VI) removal, which were found to be pH 5.0, 25°C and pH 1.0, 25°C, respectively. The adsorption isotherms were developed and it was seen that the adsorption equilibrium data fit both Freundlich and Langmuir isotherms within the studied metal ion concentrations. The adsorption constants for lead were much higher than those for chromium for both Langmuir and Freundlich models.

Investigation of Biosorption of Chromium(VI) on Cladophora Crispata in Two-Staged Batch Reactor

In this study, the adsorption of chromium(VI) to C. crispata was investigated in a two-staged batch reactor. The sorption phenomenon was expressed by the Freundlich adsorption isotherm and this expression was used for the calculation of the equilibrium value of the residual or adsorbed chromium(VI) concentration(Ceq or Cxeq) at each stage for a given “quantity of alga/volume of waste water containing chromium(VI)” or (Xo/Vo) ratio in a two-staged batch reactor. Experimental Ceq values were compared to calculated ones at each stage. Applications in waste water treatment for chromium(VI) removal have been suggested.

A staged purification process to remove heavy metal ions from wastewater using Rhizopus arrhizus

Abstract The adsorption of iron(III), lead(II) and cadmium(II) ions onto dry cells of Rhizopus arrhizus was investigated in a four-stage batch reactor. The adsorption in multi-stage reactors can be considered as a multi-stage equilibrium depending on the adsorption equilibrium and mass balance. The Freundlich and Langmuir adsorption isotherms were developed to evaluate the biosorptive uptake capacity of the biomass. The Freundlich and Langmuir constants at optimum adsorption conditions were used to calculate the residual or adsorbed metal ion concentrations at equilibrium at each stage for a given volume of solution containing heavy metal ion/quantity of dried biomass ( V 0 X ) ratio. The experimental equilibrium values were compared with the values obtained from Freundlich and Langmuir isotherm equations. These results showed that the increase in biomass quantity or the decrease of V 0 X ratios affected the quantities of iron, lead and cadmium removed from aqueous solution.

Investigation of zinc(II) adsorption on Cladophora crispata in a two-staged reactor

In this study, the adsorption of zinc(II) ions on Cladophora crispata, a green alga, was studied with respect to initial pH, temperature, initial metal ion and biomass concentration in order to determine the optimum adsorption conditions. Optimum initial pH values for zinc(II) ions were found to be 5.0 at optimum temperature, 25 °C. The initial adsorption rates increased with increasing initial zinc(II) ion concentration up to 100 mgdm−3. The Freundlich and Langmuir adsorption isotherms were developed at various initial pH and temperature values. Then, the adsorption of zinc(II) ions to C crispata was investigated in a two-staged mixed batch reactor. The residual metal ion concentrations (Ceq) at equilibrium at each stage for a given quantity of dried algae (Xo)/volume of solution containing heavy metal ion (Vo) ratio were calculated by using Freundlich and Langmuir isotherm constants. It was observed that the experimental biosorption equilibrium data for zinc(II) ions are in good agreement with those calculated using both Freundlich and Langmuir models. The adsorbed zinc(II) ion concentration increased with increasing Xo/Vo ratios while the adsorbed metal quantities per unit mass of dried algae decreased. © 2000 Society of Chemical Industry