Y.K. Bayhan’s research while affiliated with Atatürk University and other places

In this study, biosorption of Cr (VI) ion was investigated by using biomass of Agaricus bisporus (a species of mushroom) in a temperature and shaking speed controlled shaker. The effect of shaking speed, biomass concentration, initial metal ion concentration and initial pH on biosorption yield was determined and the fitness of biosorption data for Freundlich and Langmuir adsorption models was investigated. Optimum biosorption conditions were found to be pH 1, C0=50 mg/l, m=10 g/l, shaking speed=150 rpm, T=20 degrees C Cr (VI), respectively. It was found that biosorption of Cr (VI) ions onto biomass of A. bisporus was better suitable to Freundlich adsorption model than Langmuir adsorption model. The correlation coefficients for the second-order kinetic model obtained were found to be 0.999 for all concentrations. These indicate that the biosorption system studied belongs to the second-order kinetic model.

Biosorption equilibrium, kinetics and thermodynamics of chromium(VI) ions onto cone biomass were studied in a batch system with respect to temperature and initial metal ion concentration. The biosorption efficiency of chromium ions to the cone biomass decreased as the initial concentration of metal ions was increased. But cone biomass of Pinus sylvestris Linn. exhibited the highest Cr(VI) uptake capacity at 45 degrees C. The biosorption efficiency increased from 67% to 84% with an increase in temperature from 25 to 45 degrees C at an initial Cr(VI) concentration of 300 mg/L. The Langmuir isotherm model was applied to experimental equilibrium data of Cr(VI) biosorption depending on temperature. According to Langmuir isotherm, the monolayer saturation capacity (Q(max)) is 238.10 mg/g. The pseudo-first-order and pseudo-second-order kinetic models were applied to test the experimental data for initial Cr(VI). The pseudo-second-order kinetic model provided the best correlation of the used experimental data compared to the pseudo-first-order kinetic model. The activation energy of biosorption (E(a)) was determined as 41.74 kJ/mol using the Arrhenius equation. Using the thermodynamic equilibrium coefficients obtained at different temperatures, the thermodynamic constants of biosorption (DeltaG(0), DeltaH(0) and DeltaS(0)) were also evaluated.

Biosorption of heavy metals can be an effective process for the removal of heavy metal ions from aqueous solutions. In this study, the adsorption properties of lichen biomass of Cladonia rangiformis hoffm. for copper(II) were investigated by using batch adsorption techniques. The effects of initial metal ion concentration, initial pH, biosorbent concentration, stirring speed and contact time on biosorption efficiency were studied. In the experiments the optimum pH value was found out 5.0 which was the native pH value of solution. The experimental adsorption data were fitted to the Langmuir adsorption model. The highest metal uptake was calculated from Langmuir isotherm and found to be 7.6923 mg Cu(II)/g inactivated lichen at 15 degrees C. The results indicated that the biomass of C. rangiformis is a suitable biosorbent for removing Cu(II) from aqueous solutions.

The removal of chromate anions (CrO(4)(2-)) from aqueous solution by a cationic surfactant-modified yeast was studied in a batch system. Cetyl trimethyl ammonium bromide (CTAB) was used for biomass modification; it substantially improved the biosorption efficiency. The influences of solution pH, CrO(4)(2-) anion concentrations and biomass concentration on the biosorption efficiency were investigated. The biosorption of chromate anions by modified yeast was strongly affected by pH. The optimum pH for biosorption of CrO(4)(2-) by modified yeast was 4.5-5.5. Zeta potential values of modified and unmodified yeast were determined at various pH values. Concentrations ranging from 5.2 to 208 mg/l Cr(VI) were tested and the biosorptive removal efficiency of the metal ions from aqueous solution was more than 99.5%. Freundlich and Langmuir isotherms were used to evaluate the data and the regression constants were determined.

Crossflow microfiltration of low concentration-nonliving yeast suspension was studied and effects of transmembrane pressure drop (ΔP), membrane pore size and crossflow velocity on the membrane fluxes have been investigated. Filtration mechanism was explained by various flux decline models such as standard, intermediate, complete blocking and cake filtration. It was shown that permeate flux decay could be divided into three distinctive regions such as constant, rapid flux decay and slow flux decay periods by using relations of J(t)–t, t/V–V and V–t on the same plot. It was concluded that flux decline model fit to intermediate blocking model at the beginning of the filtration and then classical cake filtration became dominant filtration mechanism. It was found that specific cake resistance increased with increasing ΔP. Compressibility coefficient (n) was calculated to be 1 and 0.39 for crossflow and dead-end filtration modes, respectively. Steady-state permeate fluxes increased with membrane pore size and crossflow velocity, and decreased with increasing yeast concentration. It was determined that pseudo-gel concentration on the membrane surface was 45 g/l and it was independent from crossflow velocity and membrane pore size.

Biosorption of chromium(VI) on to cone biomass of Pinus sylvestris was studied with variation in the parameters of pH, initial metal ion concentration and agitation speed. The biosorption of Cr(VI) was increased when pH of the solution was decreased from 7.0 to 1.0. The maximum chromium biosorption occurred at 150 rpm agitation. An increase in chromium/biomass ratio caused a decrease in the biosorption efficiency. The adsorption constants were found from the Freundlich isotherm at 25 degrees C. The cone biomass, which is a readily available biosorbent, was found suitable for removing chromium from aqueous solution.

This work presents an investigation on the changes in some characteristics of the soil due to the cement dust of air originated pollutants emitted from Erzurum-Askale Cement Plant. The comparative examination showed that the pollution caused an increase of 22.00% in lime, 15.93% in exchangeable cation, and therefore, 12 66% in pH and 7.86% in electrical conductivity. The sand and clay amounts were also observed to increase. These changes resulted in a decrease of 6.5% in organic matter content, 37.01% in field capacity and 32.52% in wilting point in polluted region. Since all these changes affect negatively the quality of the soil, the ecology controlling the microbial activities breaks down, affecting negatively the developments of the plants in the polluted region. The factory was refitted with a dust filtration system after this work.

In this study, the effects of various metal ions, Al3+, Cu2+, Ni2+, Pb2+ and Na+, on the transient and steady-state crossflow microfiltration behaviour of dilute yeast cell suspensions are investigated. It is observed that in the presence of Pb2+ and Al3+ specific cake resistance decreases, while steady-state permeate flux increases. At the same concentration levels, cake resistance for Al3+ is lower compared with Pb2+. Microscopic examinations of the yeast suspension indicate higher levels of yeast cell aggregation in the presence of Al3+ than Pb2+. The specific cake resistance increases with increasing concentrations of Na+, Ni2+ and Cu2+ ions whereas the steady-state fluxes decrease. In these cases, cell aggregation is not present except when the concentration of Cu2+ is 0.4 mM. Consequently, at this concentration level, significant decrease in specific cake resistance is present. The order of the binding affinity of the metals to yeast cell is Al3+>Pb2+>Cu2+>Ni2+ which is also reflected in the metal ion rejection under identical processing conditions.

The removal of heavy metal ions, Ni2+, Cu2+ and Pb2+ using yeast (Saccharomyces cerevisiae) as carriers in a crossflow microfiltration is investigated. The effects of yeast cell and electrolyte concentrations on the transient and steady-state permeate flux and metal ion rejections are established. It is found that the metal ion rejection reaches a plateau if yeast cell concentration is greater than approximately 2 g/l as a result of cell aggregation. The binding affinity of the metals to yeast cell is Pb2+ > Cu2+ > Ni2+, which is also reflected in the metal ion rejection under identical process conditions. Because of the formation of yeast cell flocks in the presence of Pb2+, permeate flux is also higher for this metal. The presence of NaCl decreases both rejection and permeate flux for Ni2+ and Cu2+ but not for Pb2+. When binary or ternary metal mixtures are used, the rejection of the individual metals is reduced except that of Pb2+. It is found that the pseudo-gel concentration is unaffected by the presence of metal ions.