Kinetics studies of synthesis of biodiesel from waste frying oil using a heterogeneous catalyst derived from snail shell.

Waste frying oil was used to produce biodiesel using calcined snail shell as a heterogeneous base catalyst. Trans esterification reactions were carried out and the yield and conversion of the product were optimized by varying the methanol to oil molar ratio, catalyst amount, reaction temperature, and time. A biodiesel conversion of 99.58% was obtained with a yield of 87.28%. The reaction followed first order kinetics. The activation energy (E(A)) was 79kJ/mol and the frequency factor (A) was 2.98×10(10)min(-1). The fuel properties of the biodiesel were measured according to ASTM D 6751 and found to be within the specifications. Snail shell is a novel source for the production of heterogeneous base catalyst that can be successfully utilized for synthesis of biodiesel of high purity.

Magnetic Fe3O4 nanoparticles for adsorptive removal of acid dye (new coccine) from aqueous solutions.

The ability of magnetic Fe3O4 nanoparticles (MFN) to remove new coccine (NC), an acidic dye, from aqueous solutions was studied. Parameters including ionic strength, pH, and temperature were evaluated. MFN, prepared by precipitation method, exhibits an average particle size of 12.5 nm, specific surface area of 85.5 m²/g, and pH(zpc) of 5.9. Results of kinetic adsorption experiments indicated that the pseudo-second-order rate of adsorption increased with increasing initial NC concentration. Findings also revealed that the equilibrium data could be fitted into Langmuir adsorption isotherm. The adsorption is favored at low pH, high temperature, and low ionic strength, whereupon a maximum adsorption capacity of 1.11 x 10⁻4 mol/g was determined for NC. Thermodynamic functions indicated that the adsorption process is spontaneous and exothermic in nature. Tests of regeneration showed that after 5 regeneration cycles the adsorption capacity of NC decreased to 35% to its original capacity.

Reverse micelles for the removal of dyes from aqueous solutions.

The ability of reverse micelles to solvate organic dyes in the aqueous core was investigated with methyl orange (MO) and methylene blue (MB) using hexadecyl trimethyl ammonium bromide (HTAB) and sodium dodecyl benzene sulphonate (SDBS) surfactants in a polar amyl alcohol medium. The removal trend of the dyes from water was studied with different concentrations of the dyes. The effects of NaCl and CaCl2 salts on removal efficiency of the surfactants were investigated and results were compared. It was observed that the separation of dyes from the aqueous phase to the organic phase depends on the electrostatic interaction between the dye molecule and surfactant head groups. In the case of NaCl, with increasing salt concentration, the removal (%) of dye decreases. For CaCl2, removal of methyl orange shows a gradual increase with increasing dye concentration, whereas, for methylene blue, its removal decreases with increasing dye concentration.

Nano-adsorbents for the removal of metallic pollutants from water and wastewater.

Of the variety of adsorbents available for the removal of heavy and toxic metals, activated carbon has been the most popular. A number of minerals, clays and waste materials have been regularly used for the removal of metallic pollutants from water and industrial effluents. Recently there has been emphasis on the application of nanoparticles and nanostructured materials as efficient and viable alternatives to activated carbon. Carbon nanotubes also have been proved effective alternatives for the removal of metallic pollutants from aqueous solutions. Because of their importance from an environmental viewpoint, special emphasis has been given to the removal of the metals Cr, Cd, Hg, Zn, As, and Cu. Separation of the used nanoparticles from aqueous solutions and the health aspects of the separated nanoparticles have also been discussed. A significant number of the latest articles have been critically scanned for the present review to give a vivid picture of these exotic materials for water remediation.

Biosorption studies of nickel on Parthenium hysterophorous ash.

The application of an aquatic weed, Parthenium hysterophorous, has been investigated for the removal of nickel from aqueous solutions. Parthenium hysterophorous, the weed was converted to ash and was used as an adsorbent for the removal of nickel(II) from aqueous solutions at different experimental conditions. The per cent removal of Ni increased from 67.30 to 97.54%, with the nickel(II) concentration decreasing from 477.21 to 67.83 mg L(-1) at 25 degrees C, pH 11.0. The removal was favoured at higher pH, with a maximum removal at pH 11.0. The effects of concentration and temperature are also reported. Batch adsorption kinetics are described by the Lagergren equation. The value of the rate constant of adsorption was found to be 6.82 x 10(-2) min(-1) at 67.83 mg L(-1) and 25 degrees C. The applicability of the Langmuir and Freundlich equations for the present system were tested at different temperatures, viz. 25, 50 and 75 degrees C, and the constants were calculated. Thermodynamic parameters indicate the exothermic nature of nickel(II) adsorption on P. hysterophorous ash. The adsorption capacity was found to be much better than other common adsorbents reported for the removal of nickel(II).

Removal of chromium by riverbed sand from water and wastewater: effect of important parameters.

Application of riverbed sand, a non-toxic substance for the removal of Cr(VI) for aqueous solutions has been investigated. Removal of Cr(VI) was dependent on initial concentration and removal increased from 43.2% to 74.3% by decreasing initial concentration from 7.5x10(-5) M to 1.0x10(-5) M at 25 degrees C, 1.0x10(-2) M NaClO4 ionic strength and 100 rpm. Higher removal was obtained at particles of smaller sizes of the adsorbent. Removal decreased from 74.3% to 40.7% by increasing temperature from 25 degrees C to 35 degrees C exhibiting exothermic nature of the process of removal. Thermodynamic parameters, namely change in free energy (DeltaG degrees), enthalpy (DeltaH degrees) and entropy (DeltaS degrees), were calculated and were found to be -0.81 kcal mol(-1), -17.21 kcal mol(-1) and 56.94 cal mol(-1), respectively at 25 degrees C. pH of the solution has pronounced effect on the removal and higher removal was obtained in acidic pH ranges, maximum (74.3%) being at 2.5 pH.

Adsorption of Cr(VI) from aqueous solutions by spent activated clay.

Adsorption of Cr(VI) onto spent activated clay (SAC), a waste produced from an edible oil refinery company, was investigated for its beneficial use in wastewater treatment. After pressure steam treatment, SAC was used as an adsorbent. The adsorption kinetic data were analyzed and fitted well in a pseudo-first-order equation and the rate of removal was found to speed up with decreasing pH and increasing temperature. Activation energy for the adsorption process was found to be 4.01-5.47 kcal/K mol. The Langmuir adsorption isotherm was used to fit the equilibrium data and the effect of pH, temperature and ionic strength were studied. The maximum adsorption capacities for Cr(VI) ranged from 0.743 to 1.422 mg/g for temperature between 4 and 40 degrees C under a condition of pH 2.0. The studies conducted show the process of Cr(VI) removal to be spontaneous at high temperature and endothermic in nature. From the waste utilization and environment point of view, the work carried out is important and useful. Results obtained can serve as baseline data for designing a treatment process using this low-cost adsorbent for the treatment of wastewater rich in Cr(VI).

Adsorptive separation of cadmium from aqueous solutions and wastewaters by riverbed sand.

Application of riverbed sand for the adsorptive separation of cadmium(II) from aqueous solutions has been investigated. Removal increased from 26.8 to 56.4% by decreasing the initial concentration of cadmium from 7.5 x 10(-5) to 1.0 x 10(-5)M at pH 6.5, 25 degrees C temperature, agitation speed of 100 rpm, 100 microm particle size and 1.0 x 10(-2) NaClO4 ionic strength. Process of separation is governed by first order rate kinetics. The value of rate constant of adsorption, k(ad), was found to be 2.30 x 10(-2)per min at 25 degrees C. Values of coefficient of mass transfer, beta L, were calculated and its value at 25 degrees C was found to be 1.92 x 10(-2)cm/s. Values of Langmuir constant were calculated. Values of thermodynamic parameters delta G0, delta H0 and delta S0 were also calculated and were recorded as -0.81 kcal/mol, -9.31 kcal/mol and -28.10 cal/mol at 25 degrees C. pH has been found to affect the removal of cadmium significantly and maximum removal, 58.4%, has been found at pH 8.5. Process can be used for treatment of cadmium(II) rich wastewaters.

Removal of chromium(VI) from water and wastewater by using riverbed sand: kinetic and equilibrium studies.

Cr(VI) is a priority pollutant and has been documented to be harmful to fauna, flora and human beings and chromium containing water and wastewater are hazardous. Removal of Cr(VI) by adsorption on a non-toxic natural substance, riverbed sand has been investigated. A maximum removal of 74.3% was noted at 0.50 x 10(-4)M concentration of Cr(VI) in solution. Kinetic and equilibrium studies of Cr(VI) removal have been carried out. Chemical analysis of the adsorbent revealed SiO2 to be its major component. Kinetic data of adsorption was fitted by Lagergreen's model and k(ad), the rate constant of adsorption, was found be maximum 2.69 x 10(-2)min(-1) at 25 degrees C with minimum at 35 degrees C. Values of coefficients of intra-particle diffusion and mass transfer have been determined at different values of temperature. Langmuir's model has been used for equilibrium studies and the constants have been calculated. The studies conducted show the process of Cr(VI) removal to be exothermic in nature.