Pesticides removal from waste water by activated carbon prepared from waste rubber tire.

Waste rubber tire has been used for the removal of pesticides from waste water by adsorption phenomenon. By applying successive chemical and thermal treatment, a basically cabonaceous adsorbent is prepared which has not only a higher mesopore, macropore content but also has a favorable surface chemistry. Presence of oxygen functional groups as evidenced by FTIR spectra along with excellent porous and surface properties were the driving force for good adsorption efficiency observed for the studied pesticides: methoxychlor, methyl parathion and atrazine. Batch adsorption studies revealed maximum adsorption of 112.0 mg g(-1), 104.9 mg g(-1) and 88.9 mg g(-1) for methoxychlor, atrazine and methyl parathion respectively occurring at a contact time of 60 min at pH 2 from an initial pesticide concentration of 12 mg/L. These promising results were confirmed by column experiments; thereby establishing the practicality of the developed system. Effect of various operating parameters along with equilibrium, kinetic and thermodynamic studies reveal the efficacy of the adsorbent with a higher adsorption capacity than most other adsorbents. The adsorption equilibrium data obey Langmuir model and the kinetic data were well described by the pseudo-first-order model. Applicability of Bangham's equation indicates that diffusion of pesticide molecules into pores of the adsorbent mainly controls the adsorption process. Spontaneous, exothermic and random characteristics of the process are confirmed by thermodynamic studies. The developed sorbent is inexpensive in comparison to commercial carbon and has a far better efficiency for pesticide removal than most other adsorbents reported in literature.

A comparative investigation on adsorption performances of mesoporous activated carbon prepared from waste rubber tire and activated carbon for a hazardous azo dye--Acid Blue 113.

A mesoporous carbon developed from waste tire rubber, characterized by chemical analysis, FTIR, and SEM studies, was used as an adsorbent for the removal and recovery of a hazardous azo dye, Acid Blue 113. Surface area, porosity, and density were determined. The adsorption of the dye over the prepared adsorbent and a commercial activated carbon was achieved under different pH, adsorbate concentration, sieve size, adsorbent dosage, contact time and temperature conditions. Langmuir and Freundlich adsorption isotherm models were applied and thermodynamic parameters were calculated. Kinetic studies indicated that the adsorption process follow first order kinetics and particle diffusion mechanisms are operative. By percolating the dye solution through fixed-bed columns the bulk removal of the Acid Blue 113 was carried out and necessary parameters were determined to find out the percentage saturation of both the columns. Recovery of the dye was made by eluting 0.1 M NaOH through the column.

Biosorption of nickel onto treated alga (Oedogonium hatei): Application of isotherm and kinetic models.

Oedogonium hatei was developed into an effective and efficient adsorbent for the removal of Ni(II) ions from aqueous solution. The adsorption studies of untreated and treated algal biomass (with 0.1M HCl) were compared in batch mode. Optimum biosorption conditions were determined as a function of pH, biomass dosage, contact time, and temperature and the Langmuir and Freundlich isotherms were found applicable in terms of relatively high regression values. The maximum monolayer adsorption capacity of the biosorbents (untreated and acid-treated algae), as obtained from the Langmuir adsorption isotherm, was found to be 40.9 and 44.2mg/g, respectively at 80min contact time, 5.0 pH, 0.7g/L algal dose, and 298K temperature. The thermodynamic parameters showed that the adsorption of Ni(II) ions onto algal biomass was feasible, spontaneous, and exothermic under the studied conditions. Kinetics of adsorption followed both first- and second-order rate equations and the process involving the rate-controlling step is complex involving boundary layer as well as intraparticle diffusion processes. The FTIR results of algal biomass showed that biomass has different functional groups and these functional groups are able to react with metal ion in aqueous solution. Biosorbent could be regenerated using 0.1M NaOH solution, with up to 70% recovery. The performance of this biosorbent was then compared with many other reported biosorbents for nickel removal and it was observed that the proposed adsorbent is effective in terms of its performance.

Adsorption studies on the removal of hexavalent chromium from aqueous solution using a low cost fertilizer industry waste material.

Low cost fertilizer industry waste material called carbon slurry, produced in generators of fuel oil-based industrial generators, was converted into an effective and efficient adsorbent for the removal of hexavalent chromium(VI) from aqueous solutions. The waste was chemically treated, activated, characterized, and used for the adsorption of chromium. The work involves batch experiments to investigate the effect of contact time, pH, temperature, concentration, and adsorbent dose on the extent of adsorption by carbon slurry. The maximum adsorption was found at 70min, 2.0 pH, 4.0g/L dose, and 303K temperature. Maximum adsorption capacity (15.24mg/g) of Cr(VI) on carbon slurry was observed at 100mg/L initial Cr(VI) concentration. Langmuir and Freundlich adsorption isotherm models were applied to analyze adsorption data, and both were found to be applicable to this adsorption system, in terms of relatively high regression values. Thermodynamic parameters showed that the adsorption of Cr(VI) onto carbon slurry was feasible, spontaneous, and exothermic under the studied conditions. Kinetics of adsorption was found to follow the pseudo-second-order rate equation. Column studies have been carried out to compare these with the batch capacities. The recovery of Cr(VI) and chemical regeneration of the spent column have also been tried. In all, the results indicated that the adsorbent used in this work proved to be effective material for the treatment of chromium-bearing aqueous solutions.

Biosorption of lead(II) from aqueous solutions by non-living algal biomass Oedogonium sp. and Nostoc sp.--a comparative study.

Industrial wastewaters containing heavy metals pose a major environmental problem that needs to be remedied. The present study reports the ability of two non-living (dried) fresh water algae, Oedogonium sp. and Nostoc sp. to remove lead(II) from aqueous solutions in batch system under varying range of pH (2.99-7.04), contact time (5-300 min), biosorbent dose (0.1-0.8 g/L), and initial metal ion concentrations (100 and 200mg/L). The optimum conditions for lead biosorption are almost same for the two algal biomass Oedogonium sp. and Nostoc sp. (pH 5.0, contact time 90 and 70 min, biosorbent dose 0.5 g/L and initial Pb(II) concentration 200mg/L) however, the biomass of Oedogonium sp. was found to be more suitable than Nostoc sp. for the development of an efficient biosorbent for the removal of lead(II) from aqueous solutions, as it showed higher values of q(e) adsorption capacity (145.0mg/g for Oedogonium sp. and 93.5mg/g for Nostoc sp.). The equilibrium data fitted well in the Langmuir isotherms than the Freundlich isotherm, thus proving monolayer adsorption of lead on both the algal biomass. Analysis of data shows that the process involves second-order kinetics and thermodynamic treatment of equilibrium data shows endothermic nature of the adsorption process. The spectrum of FTIR confirms that the amino and carboxyl groups on the surface of algal biomass were the main adsorption sites for lead removal. Both the biosorbents could be regenerated using 0.1 mol/L HCl solution, with upto 90% recovery. The biosorbents were reused in five biosorption-desorption cycles without a significant loss in biosorption capacity. Thus, this study demonstrated that both the algal biomass could be used as an efficient biosorbents for the treatment of lead(II) bearing wastewater streams.

Biosorption of copper(II) from aqueous solutions by Spirogyra species.

Batch studies were conducted to investigate the kinetics and isotherms of Cu(II) biosorption on the biomass of green alga Spirogyra species. It is observed that the biosorption capacity of the biomass strongly depends on pH and algal dose. The maximum biosorption capacity of 133.3 mg Cu(II)/g of dry weight of biomass was observed at an optimum pH of 5 in 120 min with an algal dose of 20 g/L. Desorption studies were conducted with 133.3 mg/g of Cu(II) loaded biomass using different desorption agents including HCl, EDTA, H2SO4, NaCl, and H2O. The maximum desorption of 95.3% was obtained with HCl in 15 min. The results indicate that with the advantages of high metal biosorption capacity and satisfactory recovery of Cu(II), Spirogyra can be used as an efficient and economic biosorbent material for the removal and recovery of toxic heavy metals from polluted water.

Phospholipase C from two bacterial strains acts differently on pure phospholipids and membrane bound glycosylphosphatidylinositol (GPI) anchors.

Phospholipase C (PLC) was purified to homogeneity from the culture filtrate of Bacillus cereus (65-fold, 540 U/mg protein) and B. thuringiensis (76-fold, 306 U/mg protein) by conventional techniques of enzyme purification. The purified enzymes have the molecular mass of 34 kDa and 38 kDa respectively, as determined by SDS-PAGE. Both the PLCs exhibited identical sensitivity to pH, temperature, cations, anions and inhibitors like glutathione and p-chloromercuribenzoate. PLC-Bc showed a preference for phosphatidylinositol, while PLC-Bt favoured phosphatidylcholine as the substrate. Although both the enzymes were able to hydrolyze pure phosphatidylinositol, distinct differences were observed in their activity on phosphatidylinositol-anchored membrane proteins. PLC-Bc cleaved and released alkaline phosphatase, a GPI-anchored marker enzyme from microsomal membranes to a greater extent, than PLC-Bt. Experiments with sperm membranes, followed by SDS-PAGE revealed that the pattern of proteins released from their GPI-anchors by PLC-Bc and PLC-Bt were dissimilar. Although some proteins were cleaved in common by both PLCs, some others including a prominent 57 kDa protein were resistant to PLC-Bt, but sensitive to cleavage by PLC-Bc. The type of modification in the GPI anchor, special environment on membranes, and relative charge of host plasma membrane to the charge of PLC may be the factors that are responsible for the differential action of two enzymes.