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%.

Biosorption of copper(II) by nonliving lichen biomass of Cladonia rangiformis hoffm.

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.

Removal of chromate anions from aqueous stream by a cationic surfactant-modified yeast.

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.

Removal of surfactants by powdered activated carbon and microfiltration.

Direct and indirect releases of large quantities of surfactants to the environment may result in serious health and environmental problems. Therefore, surfactants should be removed from water before release to the environment or delivery for public use. Using powdered activated carbon (PAC) as adsorbent and separating particles with a membrane may be an effective technique to remove surfactants. In this study, the removal of surfactants by microfiltration and PAC was investigated and the influences of the operating parameters on the effectiveness on microfiltration were determined. An anionic (LABS) and a cationic surfactant (CTAB) were selected for the experiments. A series of batch experiments were performed to determine the sorption isotherms of surfactants to PAC. Then microfiltration experiments were carried out. The results showed that formation of secondary membrane on the surface and, within the pores of the membrane, increased the retention of surfactants significantly. Increase in transmembrane pressure and pore size of the membrane decreased the rejection rates, but increase in cross-flow velocity increased the rejection rate. Temperature had no apparent affect on the efficiency of surfactant removal. Presence of electrolyte had different effects on CTAB and LABS. The rejection rates of CTAB significantly increased when the concentration of NaCl increased; however, a slight decrease was observed in the rejection rate of LABS at the same conditions.

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.