A COMPARATIVE ADSORPTION/BIOSORPTION OF PHENOL TO GRANULAR ACTIVATED CARBON AND IMMOBILIZED ACTIVATED SLUDGE IN A CONTINUOUS PACKED BED REACTOR

The potential use of Mowital B30H resin immobilized dried activated sludge as a substitute for granular activated carbon for removing phenol from aqueous solution was examined in a continuous packed bed reactor as a function of flow rate and inlet phenol concentration. The working sorption pH value was determined as 1.0 for both the sorbents, and packed bed sorption studies were performed at this pH value. The maximum specific uptakes, total adsorbed quantities, and total removals of phenol related to the effluent volumes were determined by evaluating the breakthrough curves obtained at different flow rates and different inlet phenol concentrations for each sorbent. At the lowest flow rate of 0.8 mL/min and at the inlet phenol concentration of 500 mg/L, the maximum specific uptakes and total removals of phenol were 84.0 mg/g and 27.6%, respectively, for granular activated carbon and 9.0 mg/g and 9.3%, respectively, for immobilized dried activated sludge. Data confirmed that total removals of phenol decreased with increasing flow rate and inlet phenol concentration for both immobilized dried activated sludge and granular activated carbon systems.     

Cadmium Uptake by Biosorbent Seaweeds: Adsorption Isotherms and Some Process Conditions

Abstract

Cadmium biosorption was evaluated in 15 samples of heat-inactivated seaweeds collected from the coast of Rio de Janeiro State, Brazil. The classical Langmuir and Freundlich sorption models were fitted to the results in order to test whether these equations could appropriately describe the process of passive biosorption uptake. Depending on the algal sample and on some assumptions, both models could be applied to this study. The possible ion-exchange mechanism associated with the adsorption process was also investigated, as well as the effect of pH on biosorption and re-use of the different biomasses through several biosorption/ desorption cycles.     

Biosorption of Naphthalene from Refinery Simulated Waste-Water on Blank Alginate Beads and Immobilized Dead Algal Cells

Abstract

The potential use of blank alginate beads and immobilized dead algal cells for the removal of naphthalene from aqueous solutions was investigated in this study. The effects of contact time, solution pH, and naphthalene concentration on the sorption of naphthalene on blank alginate beads or immobilized dead algal cells were studied. The effect of the presence of other pollutants on the sorption of naphthalene on immobilized dead algal cells was also studied.

Batch adsorption experiments showed that the removal of naphthalene on both sorbents was pH dependent and significant removal of naphthalene was obtained at pH 4. Dynamic sorption experiments revealed that the biosorption of naphthalene on either sorbent was rapid where the equilibrium uptake occurred within 10 minutes, and the biosorption of naphthalene on either sorbent followed the pseudo-second order kinetics. Analysis of the equilibrium sorption data showed that naphthalene sorption on either sorbent could be fitted to the Langmuir, Freundlich, and Dubinin-Radushkevich (D–R) isotherm equations. Competitive biosorption experiments showed that biosorption of naphthalene on immobilized dead algal cells was adversely affected by the presence of either heavy metals such as copper and nickel, and chelating agents such as citric acid.     

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.     

Novel biofiltration methods for the treatment of heavy metals from industrial wastewater

Most heavy metals are well-known toxic and carcinogenic agents and when discharged into the wastewater represent a serious threat to the human population and the fauna and flora of the receiving water bodies. In the present review paper, the sources have discussed the industrial source of heavy metals contamination in water, their toxic effects on the fauna and flora and the regulatory threshold limits of these heavy metals. The various parameters of the biofiltration processes, their mechanism for heavy metals removal along with the kinetics of biofilters and its modeling aspects have been discussed. The comparison of various physico-chemical treatment and the advantages of biofiltration over other conventional processes for treatment of heavy metals contaminated wastewater have also been discussed. The applications of genetic engineering in the modification of the microorganisms for increasing the efficiency of the biofiltration process for heavy metals removal have been critically analyzed. The results show that the efficiency of the process can be increased three to six folds with the application of recombinant microbial treatment.     

An investigation of heavy metal biosorption in relation to C/N ratio of activated sludge

The effect of C/N ratio of activated sludge on heavy metal biosorption was investigated. Three sets of semi-continuous reactors with different feed C/N ratios (9, 21 and 43 mg COD/mg TKN) were set up. Sorption equilibrium tests have indicated that the biosorptive capacity of activated sludge was highly dependent on metal species and the C/N ratio. The increase in C/N ratio resulted in an increase in the Cd(II) sorption capacity of activated sludge whereas it decreased the Cu(II) sorption capacity. As for Zn(II), a different behavior was observed such that, the highest and lowest capacities have occurred at C/N ratio of 21 and 43, respectively. For Ni(II) biosorption, isotherm tests produced greatly scattered data; so, it was not possible to obtain any plausible result to indicate the relationship between maximum adsorptive capacity and C/N ratio. The accompanying release of Ca(II) and Mg(II) ions and also carbohydrates into the solution during biosorption have indicated that ion exchange mechanism was involved however, was not the only mechanism during the sorption process.     

Modified barley straw as a potential biosorbent for removal of copper ions from aqueous solution

Barley straw (BS), a very low-cost material, has been utilized as a biosorbent material for the removal of copper (Cu²⁺) ions from aqueous solutions after treatment with citric acid. Barley straw was thermochemically modified with citric acid (CA–BS) for the purpose of improving the Cu²⁺ ion sorption capacity of the straw. Biosorption studies have been carried out to determine the effect of pH, adsorbent concentration, contact time, extent of modification, and adsorbate concentration on the biosorption capacity of Cu²⁺ ions by the esterified straw. The equilibrium sorption capacities of Cu²⁺ were 4.64 mg/g and 31.71 mg/g for BS and CA–BS, respectively. The optimum pH for the removal of Cu²⁺ ions by CA–BS was around pH 7.0 and the removal of Cu²⁺ ions was 88.1%. Langmuir, Freundlich, Scatchard and D–R (Dubinin–Radushkevich) isotherms have been used to characterize the observed biosorption phenomena of Cu²⁺ ions on CA–BS. The carboxyl groups on the surface of the modified barley straw were primarily responsible for the sorption of Cu²⁺ ions.     

Cadmium biosorption by a glyphosate-degrading bacterium,a novel biosorbent isolated from pesticide-contaminated agricultural soils

In this study, biosorption of cadmium (II) ions from aqueous solutions by a glyphosate degrading bacterium, Ochrobactrum sp. GDOS, was investigated in batch conditions. The isolate was able to utilize 3 mM GP as the sole phosphorous source, favorable to bacterium growth and survival. The effect of different basic parameters such as initial pH, contact time, initial concentrations of cadmium ion and temperature on cadmium uptake was evaluated. The adsorption process for Cd (II) is well fitted with Langmuir adsorption isotherm. Experimental data were also tested in terms of biosorption kinetics using pseudo-first-order and pseudo-second-order kinetic models. Maximum metal uptake q_max was obtained as 83.33 mg g⁻¹. The sorption process of cadmium onto the Ochrobactrum sp. GDOS biomass followed second-order rate kinetic (R² = 0.9986). A high desorption efficiency was obtained in pH 2. Reusability of the biomass was examined under successive biosorption–desorption cycle repeated thrice. The characteristics of the possible interactions between biosorbent and metal ions were also evaluated by scanning electron microscope (SEM), Fourier transform infrared (FT-IR) and X-ray diffraction analysis.     

Heavy metal sorption by calcium alginate beads from Laminaria digitata

Alginate with a high M/G ratio, extracted from Laminaria digitata, was evaluated for Cu(2+), Cd(2+) and Pb(2+) sorption in acidic solutions, in the form of calcium cross-linked beads. The high M/G ratio of alginate extracted from this algal species is most likely the determining factor for the increased adsorption capacity of the investigated metals, indicating that the mannuronic acid is responsible for the ion exchange mechanism. The data obtained from the batch experiments have been interpreted with Langmuir, Freundlich and Sips models. The Sips equation provided the best fit with the experimental results, indicating sorption sites heterogeneity for the material. The pH was found to have a significant effect on the process, with sorption capacity reaching a maximum at pH 4.5, indicating a competition mechanism between H(+) and metal ions. Kinetic experiments were performed at the optimum pH. For the interpretation of the kinetic experiments the Linear Adsorption Model was employed and diffusion coefficients were determined. The model fits the experimental data at higher concentrations, where the adsorbed quantity remains almost constant. Finally, a simplified expression of the batch kinetic adsorption model was employed. The model, predicts adequately, not only the diffusivity values, but also the concentration profiles inside the spherical particles.