Zümriye Aksu

Biosorption of phenol by immobilized activated sludge in a continuous packed bed: prediction of breakthrough curves

Abstract A continuous fixed bed study was carried out by using Mowital®B30H resin immobilized dried activated sludge as a biosorbent for the removal of phenol from aqueous solution. The effect of flow rate and inlet phenol concentration on the sorption characteristics of sorbent was investigated at pH 1.0. Data confirmed that the total amount of sorbed phenol and equilibrium phenol uptake decreased with increasing flow rate and increased with increasing inlet phenol concentration. Freundlich and Langmuir adsorption models have been used to represent the column equilibrium data. The results showed that the equilibrium data fitted both models within the concentration range studied. Four kinetic models; Adams–Bohart, Thomas, Clark and Yoon–Nelson models were applied to experimental data to predict the breakthrough curves and to determine the characteristic parameters of the column useful for process design. All models were found suitable for describing the whole or a definite part of the dynamic behavior of the column with respect to flow rate and inlet phenol concentration.

Equilibrium and kinetic modelling of cadmium(II) biosorption by C. vulgaris in a batch system: effect of temperature

The biosorption of cadmium(II) ions to C. vulgaris studied in a batch system with respect to the temperature, initial pH and initial metal ion concentration. The algal biomass exhibited the highest cadmium(II) uptake capacity at 20°C, at the initial pH value of 4.0 and at the initial cadmium(II) ion concentration of 200 mg l−1. Biosorption capacity decreased from 85.3 to 51.2 mg g−1 with an increase in temperature from 20 to 50°C at this initial cadmium(II) concentration. Freundlich and Langmuir isotherm models were tried to represent the equilibrium data of cadmium(II) biosorption depending on temperature. Equilibrium data fitted very well to both the models in the studied concentration range of cadmium(II) ions at all the temperatures studied. The pseudo first- and pseudo second-order kinetic models were also applied to experimental data assuming that the external mass transfer limitations in the system can be neglected and biosorption is sorption controlled. The results showed that cadmium(II) uptake process followed the second-order rate expression and adsorption rate constants decreased with increasing temperature. Using the second-order kinetic constants, the activation energy of biosorption was also evaluated.

A comparative study on heavy metal biosorption characteristics of some algae

The biosorption of copper(II), nickel(II) and chromium(VI) from aqueous solutions on dried (Chlorella vulgaris, Scenedesmus obliquus and Synechocystis sp.) algae were tested under laboratory conditions as a function of pH, initial metal ion and biomass concentrations. Optimum adsorption pH values of copper(II), nickel(II) and chromium(VI) were determined as 5.0, 4.5 and 2.0. respectively, for all three algae. At the optimal conditions, metal ion uptake increased with initial metal ion concentration up to 250 mg l−1. Experimental results also showed the influence of the alga concentration on the metal uptake for all the species. Both the Freundlich and Langmuir adsorption models were suitable for describing the short-term biosorption of copper(II), nickel(II) and chromium(VI) by all the algal species.

Equilibrium and kinetic modelling of biosorption of Remazol Black B by Rhizopus arrhizus in a batch system: effect of temperature

Abstract The biosorption of Remazol Black B, a vinyl sulphone type reactive dye, from aqueous solutions on dried Rhizopus arrhizus was studied in a batch system with respect to the temperature, initial pH and initial dye concentration. The fungal biomass exhibited the highest dye uptake capacity at 35°C, at the initial pH value of 2.0 and at the initial dye concentration of 800 mg l −1 . The Freundlich and Langmuir adsorption models were used for the mathematical description of the biosorption equilibrium and isotherm constants were evaluated at different temperatures. Equilibrium data fitted very well to the Freundlich model in the studied concentration (20–800 mg l −1 ) and temperature (25–55°C) ranges. The pseudo first- and second-order kinetic models were also applied to the experimental data assuming that the external mas transfer limitations in the system can be neglected and biosorption is chemisorption controlled. The results indicated that the dye uptake process followed the pseudo second-order rate expression and adsorption rate constants increased with increasing temperature up to 35°C and decreased with increasing concentration.

Removal of chromium(VI) from saline wastewaters by Dunaliella species

Some industrial wastewaters contain higher quantities of salts besides chromium(VI) ions so the effect of these salts on the biosorption of chromium(VI) should be investigated. The biosorption of chromium (VI) from saline solutions on two strains of living Dunaliella algae were tested under laboratory conditions as a function of pH, initial metal ion and salt (NaCl) concentrations in a batch system. The biosorption capacity of both Dunaliella strains strongly depends on solution pH and maximum. Chromium(VI) sorption capacities of both sorbents were obtained at pH 2.0 in the absence and in the presence of increasing concentrations of salt. Chromium(VI)-salt biosorption studies were also performed at this pH value. Equilibrium uptakes of chromium(VI) increased with increasing chromium(VI) concentration up to 250–300 mg l−1 and decreased sharply by the presence of increasing concentrations of salt for both the sorbents. Dunaliella 1 and Dunaliella 2 biosorbed 58.3 and 45.5 mg g−1 of chromium(VI), respectively, in 72 h at 100 mg l−1 initial chromium(VI) concentration without salt medium. When salt concentration arised to 20% (w/v), these values dropped to 20.7 and 12.2 mg g−1 of chromium(VI) at the same conditions. Both the Freundlich and Langmuir adsorption models were suitable for describing the biosorption of chromium(VI) individually and in salt containing medium by both algal species. The pseudo second-order kinetic model was successfully applied to single chromium(VI) and chromium(VI)-salt mixtures biosorption data.

A comparative adsorption/biosorption study of mono-chlorinated phenols onto various sorbents.

The potential use of dried activated sludge and fly ash as a substitute for granular activated carbon for removing mono-chlorinated phenols (o-chlorophenol and p-chlorophenol) was examined. The pollutant binding capacity of the adsorbent/biosorbent was shown to be a function of substituted group, initial pH and initial mono-chlorinated phenol concentration. The working sorption pH value was determined as 1.0 and the equilibrium uptake increased with increasing initial mono-chlorinated phenol concentration up to 500 mg dm(-3) for all the mono-chlorinated phenol-sorbent systems. The suitability of the Freundlich, Langmuir and Redlich-Peterson adsorption models to the equilibrium data were investigated for each mono-chlorinated phenol-sorbent system. The results showed that the equilibrium data for all the mono-chlorinated phenol-sorbent systems fitted the Redlich-Peterson model best within the concentration range studied.

Biosorption of reactive dyes by dried activated sludge: equilibrium and kinetic modelling

The biosorption of reactive dyes (Reactive Blue 2 - RB2 and Reactive Yellow 2 - RY2) onto dried activated sludge was investigated. The dye binding capacity of biosorbent was shown as a function of initial pH, initial dye concentration and type of dye. The equilibrium data fitted very well to both the Freundlich and Langmuir adsorption models. The results showed that both the dyes uptake processes followed the second-order rate expression.

A COMPARATIVE STUDY ON THE BIOSORPTION CHARACTERISTICS OF SOME YEASTS FOR REMAZOL BLUE REACTIVE DYE

Biosorption capacities and rates of different kinds of dried yeasts (Saccharomyces cerevisiae, Schizosaccharomyces pombe, Kluyveromyces marxianus, Candida sp., C. tropicalis, C. lipolytica, C. utilis, C. quilliermendii and C. membranaefaciens) for Remazol Blue reactive dye from aqueous solutions were compared under laboratory conditions as a function of initial pH and initial dye concentration. Optimum initial biosorption pH was determined as 2 for all the yeasts. All the yeast species showed comparable and very high dye sorption at 100 mg/l initial dye concentration. The equilibrium sorption capacity of the biomass increased with increasing initial dye concentration up to 400 mg/l for Candida sp. C. lipolytica and C. tropicalis; up to 300 mg/l for C. quilliermendii and C. utilis and up to 200 mg/l for S. cerevisiae, S. pombe, K. marxianus and C. membranaefaciens while the adsorption yield of dye showed the opposite trend for all the yeasts. Among the nine yeast species, C. lipolytica exhibited the highest dye uptake capacity (Q(0) = 250 mg/g). Both the Freundlich and Langmuir adsorption models were found suitable for describing the biosorption of the dye by all the Candida yeasts (except C. membranaefaciens). The results indicated that the dye uptake process followed the pseudo-second-order kinetics for each dye-yeast system.

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.

Equilibrium modelling of individual and simultaneous biosorption of chromium(VI) and nickel(II) onto dried activated sludge.

The biosorption of chromium(VI) and nickel(II) ions, both singly and in combination, by dried activated sludge was investigated in a batch system as a function of initial pH and single- and dual-metal ion concentrations. The working initial pH values for single chromium(VI) and nickel(II) biosorptions were determined as 1.0 and 4.5, respectively. It was observed that the co-ion effect on the equilibrium uptake became more pronounced as the co-ion concentration in solution increased and pH level increased for chromium(VI) and decreased for nickel(II). Adsorption isotherms were developed for both the single- and dual-metal ion systems at these two pH values and expressed by the mono- and multi-component Langmuir and Freundlich adsorption models and model parameters were estimated by the non-linear regression. It was seen that the mono-component adsorption equilibrium data fitted very well to both the mono-component adsorption models for both the components and the pH values studied while the multi-component Freundlich adsorption model adequately predicted the multi-component adsorption equilibrium data at moderate ranges of initial mixture concentrations for both the studied pH values.