Vandana Singh; Tulika Malviya; Sneha Joshi; Angela Singh; Devendra N. Tripathi
Abstract
Poly(acrylamide) has been efficiently grafted onto Cassia fistula seed gum using ceric ammonium sulphate/sodium disulphite redox system. The conditions for obtaining optimum % grafting (208 %) and % efficiency (92 %) are: acrylamide = 0.16 M, ceric ammonium sulphate = 0.026 M, sodium disulphite = 0.050 ...
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Poly(acrylamide) has been efficiently grafted onto Cassia fistula seed gum using ceric ammonium sulphate/sodium disulphite redox system. The conditions for obtaining optimum % grafting (208 %) and % efficiency (92 %) are: acrylamide = 0.16 M, ceric ammonium sulphate = 0.026 M, sodium disulphite = 0.050 M, Cassia fistula seed gum = 25 mL (0.4 % (w/v)), and temperature = 40 ± 0.2 ºC. Cassia fistula-graft-poly(acrylamide) (CF-g-PAM) was characterized using FTIR and SEM studies. CF-g-PAM could very efficiently capture “Reactive Blue (RBH5G)” dye from its aqueous solution. The copolymer did not dissolve even under highly acidic pH conditions and was able to remove 99.4 % dye from 100 mg L -1 dye solution under the optimized conditions (pH= 2, rpm = 150, adsorbent dose = 30 mg, temperature = 40 ºC, and contact time = 4 h). The adsorption equilibrium data are better explained by Freundlich isotherm, which indicated the presence of heterogeneous adsorption surface sites at CF-g-PAM. Langmuir adsorption isotherm, indicated significantly high Qmax (500 mg g -1 ) for the adsorption. The dye adsorption followed a pseudo second order kinetics (k’ = 5.3 x 10 -3 g. mg -1 min -1 ), indicating chemisorption of the dye is taking place. The kinetic study also supported the intervention of some boundary layer control. The results revealed that ceric ammonium sulphate/and sodium disulphite redox system is an efficient system for grafting poly(acrylamide) onto Cassia fistula seed gum and CF-g-PAM behaved as an efficacious adsorbent for Reactive Blue H5G dye. In future, the material may be explored for the adsorption of other anionic azo dyes and may be developed as the proficient dye adsorbent.
Somit Kumar Singh; Ananda Murthy H. C; Vandana Singh
Abstract
In the present investigation, the remediation of mercury by using the gum acacia-silica composite as an adsorbent has been studied. Experiments revealed optimum parameters which were found to be pH 6, contact time 2 hours, Hg(II) concentration of 100 ppm, reflux temperature 30 0 C and adsorbent dosage ...
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In the present investigation, the remediation of mercury by using the gum acacia-silica composite as an adsorbent has been studied. Experiments revealed optimum parameters which were found to be pH 6, contact time 2 hours, Hg(II) concentration of 100 ppm, reflux temperature 30 0 C and adsorbent dosage of 50 mg. The experimental data was subjected to modeling using the Langmuir and Freundlich isotherms. It was found that the data very well fitted to the Freundlich model. The pseudo second order kinetics confirms chemisorption with rate constant 3.1 × 10-4 gmg-1min-1. The calculated thermodynamic parameters (?G 0 , ?S 0 , ?H 0 ) revealed the exothermic and spontaneous nature of adsorption process at the solid–solution interface. The adsorbent could be recycled for six successive cycles with 31.5% loss in its efficiency. The adsorbent is found to be highly effective and economical for mercury remediation from water.
Vandana Singh; Somit Kumar Singh
Abstract
In present communication we report on Cd(II) adsorption using our recently reported material, the guar gum-silica nanocomposite. The equilibrium, thermodynamics and kinetics of Cd(II) adsorption onto composite from aqueous solution were investigated. Optimum experimental parameters were determined to ...
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In present communication we report on Cd(II) adsorption using our recently reported material, the guar gum-silica nanocomposite. The equilibrium, thermodynamics and kinetics of Cd(II) adsorption onto composite from aqueous solution were investigated. Optimum experimental parameters were determined to be pH 8, contact time 2 hours, Cd(II) concentration 100 mg/L, temperature 30 o C and adsorbent dose 10 mg. The sorption equilibrium data were modeled using the Langmuir and Freundlich isotherms where the data fitted better to Langmuir model indicating unilayer sorption, the Qmax being 666 mg/g. The kinetic data indicated chemisorption in the rate-controlling step as the pseudo-second-order model was best suited (rate constant of 2.79 × 10-4 gmg -1 min -1 at 100 mg/L Cd 2+ ). The calculated thermodynamic parameters (ΔG°, ΔS°, ΔH°) showed the adsorption to be exothermic and spontaneous with decreased randomness at the solid–solution interface. The adsorbent could be recycled for six successive cycles with 31% loss in its efficiency.
Vandana Singh; Angela Singh; Devendra Singh; Jadveer Singh; Arvind K Pandey; Tulika Malviya
Abstract
In present communication we report on the kinetic and isotherm studies on Hg(II) removal using our recently reported material, the millimeter sized hollow titania spheres (TSP). The mesoporous spheres with high surface area (11.75 m 2 /g) and bimodal pore size distribution were fabricated by a facile ...
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In present communication we report on the kinetic and isotherm studies on Hg(II) removal using our recently reported material, the millimeter sized hollow titania spheres (TSP). The mesoporous spheres with high surface area (11.75 m 2 /g) and bimodal pore size distribution were fabricated by a facile sol-gel approach using alginate-guar gum hybrid beads as the structure directing agent. In order to investigate the utility of TSP for Hg(II) adsorption, the batch adsorption experiments were conducted at various pH values (2–7), initial Hg(II) concentrations (50–300 mg/L), and TSP doses (20-100 mg) at 150 rpm, and 30 °C temperature. The spheres exhibited good capacity to adsorb Hg(II) in wide pH range (pH 3 to pH 7). It was possible to remove >95 % Hg(II) from 100 mg/L synthetic Hg(II) solution at pH 5, and 50 mg TSP dose in 10 h. The adsorption equilibrium data were better fitted to Langmuir model at low temperatures while Freundlich model become favored as the temperature was increased to 40 ºC. Langmuir adsorption isotherm study indicated that the monolayer adsorption capacity of TSP was 62.5 mg/g 62.5 mg/g 78.7 mg/g and 100 mg/g at 10, 20, 30, and 40 ºC respectively, which suggested good Hg(II) adsorption capacity of TSP. The calculated RL values evidenced the feasibility of the adsorption. Adsorption kinetic data well accorded with pseudo-second order kinetic model with the rate constant k, equal to 2.5 x 10 -4 g/mg.min 1.99 x 10 -4 g/mg.min and 0.28 x 10 -4 g/mg.min at 100, 150 and 200 mg/mL initial Hg (II) concentrations, indicating chemisorption taking place in the rate determining step. At high initial Hg(II) concentration (200 mg/mL), the adsorption was exclusively controlled by intraparticle diffusion. The study revealed the suitability of TSP for the mercury removal from wastewater.
Vandana Singh; Stuti Tiwari; Sadanand Pandey; Rashmi Sanghi
Abstract
This study puts forward the synthesis of an excellent cadmium adsorbent having unprecedented high capacity (Qmax = 5000 mg g -1 ) to capture cadmium ions from synthetic cadmium solution. To synthesize the adsorbent (A700), base catalyzed polymerization of tetra ethylorthosilicate (TEOS) was conducted ...
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This study puts forward the synthesis of an excellent cadmium adsorbent having unprecedented high capacity (Qmax = 5000 mg g -1 ) to capture cadmium ions from synthetic cadmium solution. To synthesize the adsorbent (A700), base catalyzed polymerization of tetra ethylorthosilicate (TEOS) was conducted under the sacrificial templation effect of poly(acrylamide) grafted Cassia grandis seed gum (CG) while using H2O, TEOS and EtOH in 8:1:1: ratio (v/v). The CG inspired adsorbent was characterized by FTIR, XRD and SEM, both before and after cadmium adsorption. The adsorption parameters for the synthesized adsorbent were optimized by performing the batch adsorption studies under different pH, initial cadmium concentration, adsorbent dose, and contact time. The adsorption showed pseudo second order kinetics with a rate constant of 1.55 x 10 -4 g mg -1 min -1 at 450 mg mL -1 Cd(II) concentration. The thermodynamic study showed that the adsorption is endothermic and spontaneous. The adsorbent could be successfully reused for three cycles. The present adsorbent is not only very efficient in cadmium uptake; it is greener than the contemporary porous silica adsorbents derived through templation of pure synthetic polymers or surfactants. Moreover the source polysaccharide used for its synthesis is abundant and cheap. This hybrid can utilized as versatile and sustainable adsorbent for cadmium recovery from industrial wastes.
Vandana Singh; Devendra Singh
Abstract
In the present communication, we report on diastase alpha amylase immobilization at guar gum-silica nanohybrid material (H5). The immobilized amylase (H5-Amyl) showed significantly higher bioactivity (21.62 U mg -1 ) as compared to free amylase (15.59 U mg -1 ) in solution at pH 5 and temperature 40°C. ...
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In the present communication, we report on diastase alpha amylase immobilization at guar gum-silica nanohybrid material (H5). The immobilized amylase (H5-Amyl) showed significantly higher bioactivity (21.62 U mg -1 ) as compared to free amylase (15.59 U mg -1 ) in solution at pH 5 and temperature 40°C. The kinetic parameters of the free (Km = 10.66 mg L -1 ; Vmax = 1.36 µmolemL -1 .min -1 ) and the immobilized enzyme (Km = 6.11 mg mL -1 ; Vmax = 1.45 µmolemL -1 .min -1 ) revealed that the immobilization has increased the overall catalytic property of the enzyme. The immobilized enzyme on recycling could show 87% of initial activity even in the sixth cycle. Since immobilization did not hamper the enzymatic reaction rate, the biocatalyst may be suitably exploited in food and pharmaceutical industries.
