Avni Cakici

Biosorption of chromium(VI) from aqueous solution by cone biomass of Pinus sylvestris

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.

Biosorption of lead (II) from aqueous solution by cone biomass of Pinus sylvestris

Abstract Biosorption of lead (II) onto a cone biomass of Pinus sylvestris was studied with variation in the parameters of pH, initial metal ion concentration and impeller speeds. Lead removal rate was increased at pH 4.0 and was sharply decreased when pH of the solution was decreased to 2.0. Impeller speed studies indicated maximum lead biosorption at 150 rpm and the biosorption equilibrium was established after about 1 h. The adsorption constants were found from the Freundlich isotherm at 25°C. An increase in lead/biomass ratio caused a decrease in biosorption efficiency. The cone biomass, which is a readily available biosorbent, was found suitable for removing of lead in aqueous solution.

Phosphate removal from water by red mud using crossflow microfiltration

Abstract Red mud (which is a waste material formed during the production of alumina and primarily contains ferric and aluminium oxides) was used as an adsorbent for the removal of phosphate ions from water using crossflow microfiltration. It is shown that phosphate ions act as a coagulant for red mud particles, forming a compressible cake with a compressibility index of unity. As shown also by dead-end filtration experiments, the cake resistance decreases with increasing phosphate concentration. The phosphate rejection is a strong function of feed dispersion pH, phosphate and red mud concentration ratio as well as the concentration of co-ions such as sulphate ions used to adjust the dispersion pH. Under certain conditions, especially when pH=5.2, steady state permeate flux and phosphate rejection reach a maximum with 100% rejection achievable. The permeate also contain metal ion impurities originating from red mud and their concentrations increase with increasing red mud concentration and decreasing pH. The effects of other process variables, crossflow velocity and membrane pore size on phosphate rejection and permeate flux are also studied.

Removal of divalent heavy metal mixtures from water by Saccharomyces Cerevisiae using crossflow microfiltration

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.

Biosorption of chromate anions from aqueous solution by a cationic surfactant-modified lichen (Cladonia rangiformis (L.))

Biosorption has been appearing as a useful alternative to conventional treatment systems for the removal of toxic metals from aqueous stream. The batch removal of chromate anions (CrO(4)(2-)) from wastewater under different experimental conditions using a cationic surfactant-modified lichen (Cladonia rangiformis (L.)) was investigated in this study. Cetyl trimethyl ammonium bromide (CTAB) was used for biomass modification. The results of the experiments showed that biomass modification substantially improved the biosorption efficiency. Effects of pH, biosorption time, initial CrO(4)(2-) concentration, biosorbent dosage, and the existence of the surfactant on the biosorption of CrO(4)(2-) anions were studied. Studies up to date have shown that the biosorption efficiency of chromium increased as the pH of the solution decreased. In the present study, the removal of chromate anions from aqueous solutions at high pH values with surfactant-modified lichen was investigated. From the results of the experiments it was seen that the removal of chromate anions by modified lichen was 61% at the solution natural pH (pH 5.11) but at the same pH value the removal of chromate anions by unmodified lichen was 6%. Also concentrations ranging from 30 to 150 mg/L Cr(IV) were tested and the biosorptive removal efficiency of the metal ions from aqueous solution at high pH was achieved more than 98%.

An approach to controlling sludge age in the activated sludge process

Abstract Development of better design and control methods is an obvious way for improving plant operation and performance in an activated sludge process. A different approach to the control systems in the activated sludge wastewater treatment process is presented. This system is based on the control of the sludge age ( Θ c ) and the microorganism concentration (MLSS) in the aerator, by adjusting the sludge recycle and wastage flow rates, respectively.

Effect of pulsed flow on the performance of carbon felt electrode

The effect of pulsed flow on mass transfer in an electrolytic reactor was investigated using carbon felt electrode arranged in a way that the electrolyte and the current flows were parallel to each other. In these experiments, a solution of potassium ferri- and ferro-cyanide with inactive compound of sodium hydroxide was employed. The electrolyte superficial velocity was in the range 0.000429-0.00182 m/s. The frequency and the normalised amplitude of the pulse in the flow rate were changed in the range 0.17-3.55 s -1 and 0.0035-0.01 m, respectively. The experiments showed that the pulsed flow increased significantly the transfer of reacting ions onto the electrode surface up to a frequency of 1.5 s -1 and over this frequency the current ratio was effected slightly with increasing frequency. The increasing amplitude also had a positive effect on transfer rate, but not as pronounced as the frequency. An increase in the mass transfer rate between approximately 6.8 and 33.5 times of those of the flow with no pulse was obtained, depending upon the experimental conditions.