Efficiency of acid–base treated raw laterite (RL) is investigated for removal of fluoride. FTIR, ... more Efficiency of acid–base treated raw laterite (RL) is investigated for removal of fluoride. FTIR, SEM-EDX, and surface area analyzer are used to characterize the treated laterite (TL). The batch adsorption of fluoride is explored using TL under varying process conditions like adsorbent dose, pH of solution, temperature, particle size and contact time. The adsorption isotherm data of fluoride ions on
A simple shrinking core model is applied to predict the adsorption kinetics of arsenite and arsen... more A simple shrinking core model is applied to predict the adsorption kinetics of arsenite and arsenate species onto natural laterite (NL) in a stirred tank adsorber. The proposed model is a two-resistance model, in which two unknown parameters, external mass transfer coefficient (K(f)) and pore diffusion coefficient (D(e)) are estimated by comparing the simulation concentration profile with the experimental data using a nonlinear optimization technique. The model is applied under various operating conditions, e.g., initial arsenic concentration, NL dose, NL particle size, temperature, stirring speed, etc. Estimated values of D(e) and K(f) are found to be in the range of 2.2-2.6 x 10(-11)m(2)/s and 1.0-1.4 x 10(-6)m/s at 305K for different operating conditions, respectively. D(e) and K(f) values are found to be increasing with temperature and stirrer speed, respectively. Calculated values of Biot numbers indicate that both external mass transfer and pore diffusion are important during the adsorption. The model is also applied satisfactorily to predict the arsenic adsorption kinetics of arsenic contaminated groundwater-NL system and can be used to scale up.
Journal of Environmental Science and Health Part A-toxic/hazardous Substances & Environmental Engineering, 2010
Iron oxide impregnated tamarind hull carbon (IOITHC) was developed for use as an adsorbent for th... more Iron oxide impregnated tamarind hull carbon (IOITHC) was developed for use as an adsorbent for the removal of As(V) from water. Tamarind hull was used as the source of carbonaceous material, which was first treated with ferric chloride and ammonium hydroxide solutions with successive calcination at 873–974 K in a muffle furnace for 1 h to prepare an arsenic adsorbent. The B.E.T surface area of IOITHC was found to be 304.6 m2 g−1 and the average iron content in the adsorbent was found to be 7 wt%. The point of zero charge (pHzpc) of IOITHC was found to be 6.9. As(V) and arsenic (as total) adsorption on IOITHC were investigated in batch mode using As(V) spiked distilled water and real contaminated groundwater (CGW). The effects of speed of agitation, adsorbent particle size, temperature, pH of the solution, and concentration of the adsorbate on the adsorption process were investigated. The maximum adsorption capacity of about 1.2 mg g−1 As(V) was achieved. The removal of As(V) on IOITHC was compared with the untreated tamarind hull carbon as well as with the activated commercial carbon and IOITHC was found to be better adsorbent. Arsenic adsorption from arsenic contaminated groundwater (CGW) on IOITHC in batch mode indicates that 98% removal was achieved for adsorbent loading of 3.0 g L−1 with initial arsenic concentration of 264 μg L−1. Desorption study of arsenic from As(V)-loaded IOITHC was performed using aqueous solution in the pH range of 3 to 12.
International Journal of Environmental Technology and Management, 2010
ABSTRACT Desorption kinetics of arsenite- and arsenate-loaded Natural Laterite (NL) is performed ... more ABSTRACT Desorption kinetics of arsenite- and arsenate-loaded Natural Laterite (NL) is performed under varying NaOH concentration (0.05-0.3 mol/L) and pH (4.0-11.0) of the desorption medium. The kinetic desorption data are well fitted to pseudo-second order kinetic model. The leaching of NL under aqueous medium is performed in the pH range of 2-12. Separately arsenite- and arsenate-loaded NL is leached according to Toxicity Characteristic Leaching Procedure (TCLP) protocol. However, recent studies indicate that TCLP significantly underestimate the leaching behaviour of arsenic. So, arsenic leaching from arsenic-loaded NL is conducted under synthetic leachate condition and results are compared with TCLP results.
... The silicate ion concentration was measured using Nickel and Brummer's m... more ... The silicate ion concentration was measured using Nickel and Brummer's method.(28) Chloride and fluoride ion measurement was performed using an Orion ion selective electrode meter (model Orion 720A+, Thermo Electron Corporation, Beverly, USA). ...
Electronic emission spectral characteristics of a ketocyanine dye have been studied in solution i... more Electronic emission spectral characteristics of a ketocyanine dye have been studied in solution in presence of lithium perchlorate. Steady state emission spectrum can be separated into two Gaussian curves which points to the existence of two emitting species viz, the solvated and the complexed dye in equilibrium. Time-resolved studies of the dye solutions containing lithium perchlorate can be explained by
Electronic absorption and emission spectral characteristics of a ketocyanine dye have been studie... more Electronic absorption and emission spectral characteristics of a ketocyanine dye have been studied in acetonitrile solution in presence of perchlorate salts of lithium and magnesium. Absorption spectral studies indicate complex formation between metal ions and the dye in the ground state. The value of equilibrium constant has been determined for the dye cation interaction. The energy of maximum fluorescence shifts
Spectrochimica Acta Part A-molecular and Biomolecular Spectroscopy, 2005
Interaction between 3d-transition metal ions (Mn2+, Fe2+, Fe3+, Co2+, Ni2+, Cu2+ and Zn2+) and th... more Interaction between 3d-transition metal ions (Mn2+, Fe2+, Fe3+, Co2+, Ni2+, Cu2+ and Zn2+) and the E(T)(30) dye, 2,6-diphenyl-4-(2,4,6-triphenyl 1-pyridino)phenolate in aqueous medium have been studied by distributing the dye between the aqueous and micellar phase formed by cationic surfactant cetyltrimethylammonium bromide(CTAB). Values of equilibrium constant K for the dye-metal ion interaction and the partition coefficient of the dye between the micellar and the aqueous phase have been determined. K values show a systematic correlation with ionic potential of metal ions.
Electronic absorption and emission spectral characteristics of a ketocyanine dye have been studie... more Electronic absorption and emission spectral characteristics of a ketocyanine dye have been studied in solution in the presence of lithium perchlorate. Absorption spectral studies indicate complex formation between lithium ion and the dye in the ground state. The value of the equilibrium constant along with the molar absorbance of the absorbing species has been determined for the dye-cation interaction. The energy of maximum fluorescence shifts toward the red with the addition of LiClO(4). Steady-state emission studies point to the existence of two emitting species, viz., the solvated and the complexed dye in equilibrium. The values of the equilibrium constant for the process have been determined in acetone and acetonitrile. Time-resolved studies in the picosecond domain in pure solvents reveal that the lifetime (tau) value increases as the solvation interaction increases. Time-resolved studies also indicate the presence of two emitting species in equilibrium.
In this study, castor oil is hydrolyzed in presence of Candida rugosa lipase, while in the buffer... more In this study, castor oil is hydrolyzed in presence of Candida rugosa lipase, while in the buffer (aqueous) phase as a dispersion medium. The following conditions were used to optimize the process: speed of agitation, initial pH of buffer phase, temperature, and ratio of buffer phase volume to oil weight. The optimal conditions are 1,100 rpm, pH 6.5, temperature 35°C, and 3:1 buffer phase volume to oil weight ratio. Under these described conditions, the reusability of lipase was tested and it was found that nearly 80% of original hydrolysis percentage was achieved after the first recycle.
Application of mixed surfactants coupled with statistical optimization in lipase catalyzed oil hy... more Application of mixed surfactants coupled with statistical optimization in lipase catalyzed oil hydrolysis is presented for the first time in this study. Selective hydrolysis of brown mustard oil to erucic acid by porcine pancreas lipase was enhanced by mixed surfactants comprising of an oil-soluble nonionic surfactant (Span 80) and a watersoluble nonionic surfactant (Tween 80). The production of erucic acid was maximized using statistically designed experiments and subsequent analysis of their result by response surface methodology. The most significant variables were enzyme concentration and concentration of Tween 80. Small changes in pH and concentration of Span 80 also produced a significant change in the production of erucic acid. Temperature and speed of agitation were insignificant variables and were fixed at 35oC and 900 rpm, respectively. Under these conditions, the optimal combination of other variables were pH 9.65, 2.13 mg/g enzyme in oil, 9.8 × 10−3 M Span 80 (in oil), and 4 × 10−3 M Tween 80 (in buffer). These conditions led to formation of 99.69% of the total erucic acid in 1.25 h. Interaction of enzyme concentration with pH significantly affected erucic acid production.
Efficiency of acid–base treated raw laterite (RL) is investigated for removal of fluoride. FTIR, ... more Efficiency of acid–base treated raw laterite (RL) is investigated for removal of fluoride. FTIR, SEM-EDX, and surface area analyzer are used to characterize the treated laterite (TL). The batch adsorption of fluoride is explored using TL under varying process conditions like adsorbent dose, pH of solution, temperature, particle size and contact time. The adsorption isotherm data of fluoride ions on
A simple shrinking core model is applied to predict the adsorption kinetics of arsenite and arsen... more A simple shrinking core model is applied to predict the adsorption kinetics of arsenite and arsenate species onto natural laterite (NL) in a stirred tank adsorber. The proposed model is a two-resistance model, in which two unknown parameters, external mass transfer coefficient (K(f)) and pore diffusion coefficient (D(e)) are estimated by comparing the simulation concentration profile with the experimental data using a nonlinear optimization technique. The model is applied under various operating conditions, e.g., initial arsenic concentration, NL dose, NL particle size, temperature, stirring speed, etc. Estimated values of D(e) and K(f) are found to be in the range of 2.2-2.6 x 10(-11)m(2)/s and 1.0-1.4 x 10(-6)m/s at 305K for different operating conditions, respectively. D(e) and K(f) values are found to be increasing with temperature and stirrer speed, respectively. Calculated values of Biot numbers indicate that both external mass transfer and pore diffusion are important during the adsorption. The model is also applied satisfactorily to predict the arsenic adsorption kinetics of arsenic contaminated groundwater-NL system and can be used to scale up.
Journal of Environmental Science and Health Part A-toxic/hazardous Substances & Environmental Engineering, 2010
Iron oxide impregnated tamarind hull carbon (IOITHC) was developed for use as an adsorbent for th... more Iron oxide impregnated tamarind hull carbon (IOITHC) was developed for use as an adsorbent for the removal of As(V) from water. Tamarind hull was used as the source of carbonaceous material, which was first treated with ferric chloride and ammonium hydroxide solutions with successive calcination at 873–974 K in a muffle furnace for 1 h to prepare an arsenic adsorbent. The B.E.T surface area of IOITHC was found to be 304.6 m2 g−1 and the average iron content in the adsorbent was found to be 7 wt%. The point of zero charge (pHzpc) of IOITHC was found to be 6.9. As(V) and arsenic (as total) adsorption on IOITHC were investigated in batch mode using As(V) spiked distilled water and real contaminated groundwater (CGW). The effects of speed of agitation, adsorbent particle size, temperature, pH of the solution, and concentration of the adsorbate on the adsorption process were investigated. The maximum adsorption capacity of about 1.2 mg g−1 As(V) was achieved. The removal of As(V) on IOITHC was compared with the untreated tamarind hull carbon as well as with the activated commercial carbon and IOITHC was found to be better adsorbent. Arsenic adsorption from arsenic contaminated groundwater (CGW) on IOITHC in batch mode indicates that 98% removal was achieved for adsorbent loading of 3.0 g L−1 with initial arsenic concentration of 264 μg L−1. Desorption study of arsenic from As(V)-loaded IOITHC was performed using aqueous solution in the pH range of 3 to 12.
International Journal of Environmental Technology and Management, 2010
ABSTRACT Desorption kinetics of arsenite- and arsenate-loaded Natural Laterite (NL) is performed ... more ABSTRACT Desorption kinetics of arsenite- and arsenate-loaded Natural Laterite (NL) is performed under varying NaOH concentration (0.05-0.3 mol/L) and pH (4.0-11.0) of the desorption medium. The kinetic desorption data are well fitted to pseudo-second order kinetic model. The leaching of NL under aqueous medium is performed in the pH range of 2-12. Separately arsenite- and arsenate-loaded NL is leached according to Toxicity Characteristic Leaching Procedure (TCLP) protocol. However, recent studies indicate that TCLP significantly underestimate the leaching behaviour of arsenic. So, arsenic leaching from arsenic-loaded NL is conducted under synthetic leachate condition and results are compared with TCLP results.
... The silicate ion concentration was measured using Nickel and Brummer's m... more ... The silicate ion concentration was measured using Nickel and Brummer's method.(28) Chloride and fluoride ion measurement was performed using an Orion ion selective electrode meter (model Orion 720A+, Thermo Electron Corporation, Beverly, USA). ...
Electronic emission spectral characteristics of a ketocyanine dye have been studied in solution i... more Electronic emission spectral characteristics of a ketocyanine dye have been studied in solution in presence of lithium perchlorate. Steady state emission spectrum can be separated into two Gaussian curves which points to the existence of two emitting species viz, the solvated and the complexed dye in equilibrium. Time-resolved studies of the dye solutions containing lithium perchlorate can be explained by
Electronic absorption and emission spectral characteristics of a ketocyanine dye have been studie... more Electronic absorption and emission spectral characteristics of a ketocyanine dye have been studied in acetonitrile solution in presence of perchlorate salts of lithium and magnesium. Absorption spectral studies indicate complex formation between metal ions and the dye in the ground state. The value of equilibrium constant has been determined for the dye cation interaction. The energy of maximum fluorescence shifts
Spectrochimica Acta Part A-molecular and Biomolecular Spectroscopy, 2005
Interaction between 3d-transition metal ions (Mn2+, Fe2+, Fe3+, Co2+, Ni2+, Cu2+ and Zn2+) and th... more Interaction between 3d-transition metal ions (Mn2+, Fe2+, Fe3+, Co2+, Ni2+, Cu2+ and Zn2+) and the E(T)(30) dye, 2,6-diphenyl-4-(2,4,6-triphenyl 1-pyridino)phenolate in aqueous medium have been studied by distributing the dye between the aqueous and micellar phase formed by cationic surfactant cetyltrimethylammonium bromide(CTAB). Values of equilibrium constant K for the dye-metal ion interaction and the partition coefficient of the dye between the micellar and the aqueous phase have been determined. K values show a systematic correlation with ionic potential of metal ions.
Electronic absorption and emission spectral characteristics of a ketocyanine dye have been studie... more Electronic absorption and emission spectral characteristics of a ketocyanine dye have been studied in solution in the presence of lithium perchlorate. Absorption spectral studies indicate complex formation between lithium ion and the dye in the ground state. The value of the equilibrium constant along with the molar absorbance of the absorbing species has been determined for the dye-cation interaction. The energy of maximum fluorescence shifts toward the red with the addition of LiClO(4). Steady-state emission studies point to the existence of two emitting species, viz., the solvated and the complexed dye in equilibrium. The values of the equilibrium constant for the process have been determined in acetone and acetonitrile. Time-resolved studies in the picosecond domain in pure solvents reveal that the lifetime (tau) value increases as the solvation interaction increases. Time-resolved studies also indicate the presence of two emitting species in equilibrium.
In this study, castor oil is hydrolyzed in presence of Candida rugosa lipase, while in the buffer... more In this study, castor oil is hydrolyzed in presence of Candida rugosa lipase, while in the buffer (aqueous) phase as a dispersion medium. The following conditions were used to optimize the process: speed of agitation, initial pH of buffer phase, temperature, and ratio of buffer phase volume to oil weight. The optimal conditions are 1,100 rpm, pH 6.5, temperature 35°C, and 3:1 buffer phase volume to oil weight ratio. Under these described conditions, the reusability of lipase was tested and it was found that nearly 80% of original hydrolysis percentage was achieved after the first recycle.
Application of mixed surfactants coupled with statistical optimization in lipase catalyzed oil hy... more Application of mixed surfactants coupled with statistical optimization in lipase catalyzed oil hydrolysis is presented for the first time in this study. Selective hydrolysis of brown mustard oil to erucic acid by porcine pancreas lipase was enhanced by mixed surfactants comprising of an oil-soluble nonionic surfactant (Span 80) and a watersoluble nonionic surfactant (Tween 80). The production of erucic acid was maximized using statistically designed experiments and subsequent analysis of their result by response surface methodology. The most significant variables were enzyme concentration and concentration of Tween 80. Small changes in pH and concentration of Span 80 also produced a significant change in the production of erucic acid. Temperature and speed of agitation were insignificant variables and were fixed at 35oC and 900 rpm, respectively. Under these conditions, the optimal combination of other variables were pH 9.65, 2.13 mg/g enzyme in oil, 9.8 × 10−3 M Span 80 (in oil), and 4 × 10−3 M Tween 80 (in buffer). These conditions led to formation of 99.69% of the total erucic acid in 1.25 h. Interaction of enzyme concentration with pH significantly affected erucic acid production.
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