Syed Hadi Hasan

Agro-industrial waste 'wheat bran' for the biosorptive remediation of selenium through continuous up-flow fixed-bed column.

Present study deals with the utilization of an agro-industrial waste wheat bran for the remediation of selenium species, Se(IV) and Se(VI) by continuous up-flow fixed-bed column system. Laboratory-scale column tests were performed to determine potentiality of wheat bran at various bed height, flow rates and initial metal ion concentration and it was found to be very potential biosorbent as it showed good sorption capacities of 72.54 microg/g and 62.51 microg/g for Se(IV) and Se(VI) respectively. Different models like Bed Depth Service Time (BDST), Thomas and Yoon-Nelson were applied to the experimental sorption data. The data showed very good fit to BDST model and sorption capacities (N(o)) computed using BDST model were 26,664 microg/L and 26,400 microg/L for Se(IV) and Se(VI) respectively. Also Yoon-Nelson model was found to show good agreement with the experimental kinetic results as compared to the Thomas model. Wheat bran was amenable to efficient regeneration with 10% NaOH. The biosorbent retained most of its original uptake capacity over three cycles of use. The excellent reusability of the biosorbent could lead to development of a viable metal remediation technology. Life factor calculation revealed that biosorbent bed will have sufficient capacity to avoid breakthrough at time t=0 up to 12.17 cycles for Se(IV) and 6.28 cycles for Se(VI) and bed would be completely exhausted after 56.89 cycles for Se(IV) and 18.73 cycles for Se(VI).

Factorial design for the optimization of enzymatic detection of cadmium in aqueous solution using immobilized urease from vegetable waste.

Free as well as alginate immobilized urease was utilized for detection and quantitation of cadmium (Cd2+) in aqueous samples. Urease from the seeds of pumpkin (Cucumis melo), being a vegetable waste, was extracted and purified to apparent homogeneity (Sp. Activity 353 U/mg protein; A280/A260=1.12) by heat treatment at 48+/-0.1 degrees C and gel filtration through Sephadex G-200. The homogeneous enzyme preparation was immobilized in 3.5% alginate leading to 86% immobilization and no leaching of the enzyme was found over a period of 15 days at 4 degrees C. Urease catalyzed urea hydrolysis by both soluble and immobilized enzyme revealed a clear dependence on the concentration of Cd2+. The inhibition caused by Cd2+ was non-competitive (Ki=1.41 x 10(-5) M). The time dependent inhibition both in the presence and in absence of Cd2+ ion revealed a biphasic inhibition in the activity. A Response Surface Methodology (RSM) for the parametric optimization of this process was performed using two-level-two-full factorial (2(2)), central composite design (CCD). The regression coefficient, regression equation and analysis of variance (ANOVA) was obtained using MINITAB 15 software. The predicted values thus obtained were closed to the experimental value indicating suitability of the model. In addition to this 3D response surface plot and isoresponse contour plot were helpful to predict the results by performing only limited set of experiments.

Biosorption of Pb(II) from water using biomass of Aeromonas hydrophila: central composite design for optimization of process variables.

Biomass of Aeromonas hydrophila was successfully utilized for the removal of lead from aqueous solution. The effect of process variables such as pH, initial Pb(II) concentration, biomass dose and temperature on the uptake of lead were investigated using two level four factor (2(4)) full factorial central composite design with the help of MINITAB version 15 software. The predicted results thus obtained were found to be in good agreement (R(2)=98.6%) with the results obtained by performing experiments. The multiple regression analysis and analysis of variance (ANOVA) showed that the concentration has positive and temperature and biomass dose have negative whereas pH has curved relationship with the uptake of Pb(II). The maximum uptake of Pb(II) predicted by optimization plots was 122.18 mg/g at 20 degrees C, initial Pb(II) concentration of 259 mg/L, pH 5.0, temperature 20 degrees C and biomass dose 1.0 g. Langmuir isotherm model was applicable to sorption data and sorption capacity was found to be 163.3mg/g at 30 degrees C, pH 5.0 and Pb(II) concentration range 51.8-259 mg/L indicate that the biosorbent was better in comparison of the biosorbent reported in the literature. Dubinin-Radushkevich (D-R) isotherm model was also applied and it was found that sorption was chemisorption (E=12.98 kJ/mol). FT-IR studies indicate the involvement of various functional groups present on biomass surface in the sorption of Pb(II).

Biosorption of lead using immobilized Aeromonas hydrophila biomass in up flow column system: Factorial design for process optimization

Free and immobilized biomass of Aeromonas hydrophila has been utilized for the removal of Pb(II) from aqueous solution. Fitness of Langmuir sorption model to the sorption data indicated the sorption was monolayer and uptake capacity of biomass was 163.9 and 138.88 mg/g for the free and immobilized biomass respectively. 85.38% Pb(II) removal was achieved at bed height of 19 cm and flow rate of 2 mL/min and BDST model was in a good agreement with the experimental results (r(2)>0.997). An attempt has been made to optimize the process conditions for the maximum removal using Central Composite Design with the help of Minitab 15 software and the result predicted by optimization plots was 88.27% which is close to the experimental data i.e. 85.38%. Sorption-desorption studies revealed that polysulfone immobilized biomass could reused up to 16 cycles and bed was completely exhaust after 33 cycles.

Batch and continuous biosorption of Cu2+ by immobilized biomass of Arthrobacter sp.

The ability of free and polysulphone immobilized biomass of Arthrobacter sp. to remove Cu(2+) ions from aqueous solution was studied in batch and continuous systems. The Langmuir and Freundlich isotherm models were applied to the data. The Langmuir isotherm model was found to fit the sorption data indicating that sorption was monolayer and uptake capacity (Q(o)) was 175.87 and 158.7mg/g for free and immobilized biomass respectively at pH 5.0 and 30 degrees C temperature, which was also confirmed by a high correlation coefficient, a low RMSE and a low Chi-square value. A kinetic study was carried out with pseudo-first-order reaction and pseudo-second-order reaction equations and it was found that the Cu(2+) uptake process followed the pseudo-second-order rate expression. The diffusivity of Cu(2+) on immobilized beads increased (0.402x10(-4) to 0.435x10(-4)cm(2)/s) with increasing concentration from 50 to 150mg/L. The maximum percentage Cu(2+) removal (89.56%) and uptake (32.64mg/g) were found at 3.5mL/min and 20cm bed height. In addition to this the Bed Depth Service Time (BDST) model was in good agreement with the experimental data with a high correlation coefficient (>0.995). Furthermore, sorption and desorption studies were also carried out which showed that polysulphone immobilized biomass could be reused for up to six sorption-desorption cycles.

Tri-iso-amyl phosphate (TAP): An alternative extractant to tri-butyl phosphate (TBP) for reactor fuel reprocessing

Tri-iso-amyl phosphate (TAP), an indigenously prepared extractant was utilized for reactor fuel reprocessing and compared with tri-butyl phosphate (TBP) and tri-n-hexyl phosphate (THP). The potential of these extractants was found to be in the order TAP>THP>TBP by calculating the acid uptake value (KH). The effect of various parameters such as solvent degradation due to acid hydrolysis, radiation effect, decontamination factor and phase separation were investigated and it was found that TAP was always a better extractant in comparison to THP and TBP. In addition to this, the extraction of fission product contaminants such as 144Ce, 137Cs, 106Ru, 95Zr was almost negligible, even at very high nitric acid concentrations in the aqueous phase, indicating the potential application of TAP in actinide partitioning. Sodium carbonate solution or acidified distilled water was a good strippant for U(VI), similarly, uranium(IV) nitrate stripped Pu(IV) from the organic phase.

Photo-induced biosynthesis of silver nanoparticles using aqueous extract of Erigeron bonariensis and its catalytic activity against Acridine Orange.

The green synthesis of silver nanoparticles (AgNPs) has reduced the pollution load in the environment to a greater extent by avoiding the use of hazardous chemicals. In the present work we have developed an ecofriendly and zero cost approach for the green synthesis of more stable and spherical AgNPs using aqueous extract of Erigeron bonariensis (AEE) which act as both reducing and stabilizing agent. The reaction of AEE and AgNO3 was carried out in direct sunlight for the instant biosynthesis of AgNPs within minutes. The biosynthesis was monitored by UV-vis spectroscopy which exhibited a sharp SPR band at 442 nm and 435 nm after 5 and 35 min of sunlight exposure. The optimum conditions for biosynthesis of AgNPs were found to be 2.5mM AgNO3 concentration, 1.5% (v/v) of AEE inoculum dose and 35 min of sunlight exposure. Presence of spherical AgNPs with average size 13 nm was confirmed by SEM and TEM analysis. The XRD and SAED analysis confirmed the crystalline nature of the AgNPs where the Braggs diffraction pattern at (111), (200), (220) and (311) corresponded to face centered cubic crystal lattice of metallic silver. The average roughness of the synthesized AgNPs was 3.21 nm which was confirmed by AFM analysis. FTIR analysis was recorded between 4000 and 400 cm(-1) which confirmed the involvement of various functional groups in the synthesis of AgNPs. The AgNPs thus obtained showed catalytic activity towards degradation of Acridine Orange (AO) without involvement of any hazardous reducing agent. The concentration dependent catalytic activity of the synthesized AgNPs was also monitored using 1, 2 and 3 mL of silver colloids and was found that the degradation of AO followed pseudo first-order kinetics.

Photo-catalyzed and phyto-mediated rapid green synthesis of silver nanoparticles using herbal extract of Salvinia molesta and its antimicrobial efficacy

Current study presents an economic, ecofriendly and simple photo-catalytic green route for the swift biosynthesis of silver nanoparticles (AgNPs) within 20s, devoid of any instrumental support or chemical reductant. Aqueous leaf-extract of an aquatic fern, Salvinia molesta (AES), was used as a bioreductant as well as a stabilizing agent. Rapid change in color of reaction mixture from yellowish green to reddish brown within 20s in direct sun light exposure was considered as the primary visual indication of AgNPs biosynthesis. The biosynthesis of AgNPs was confirmed by UV-visible spectroscopy through the presence of a characteristic surface plasmon resonance (SPR) band for AgNPs at λmax of 425 nm. The process parameters were optimized through one factor at a time approach. Optimal values of different process parameters for the current biosynthetic system were found as; 35 min of reaction time under sun light, 8.0mM AgNO3 concentration and 5.0% (v/v) AES inoculum dose. Field emission scanning electron microscopy (FESEM), energy dispersive X-Ray spectroscopy (EDX), high resolution transmission electron microscopy (HRTEM), atomic force microscopy (AFM) and X-ray diffraction (XRD) analysis showed that most of AgNPs were spherical in shape with average size distribution of 12.46 nm having face centered cubic (fcc) crystal lattice. IR analysis of AES and synthesized AgNPs indicated the involvement of both hydroxyl and amino groups in the biosynthesis and stabilization of AgNPs. The synthesized AgNPs were found to be an effective antibacterial agent against both Gram positive and Gram negative bacteria. On the basis of results and facts, a probable mechanism has also been proposed to explore the possible route of biosynthesis of AgNPs through AES.

Photo-mediated optimized synthesis of silver nanoparticles for the selective detection of Iron(III), antibacterial and antioxidant activity

The AgNPs synthesized by green method have shown great potential in several applications such as biosensing, biomedical, catalysis, electronic etc. The present study deals with the selective colorimetric detection of Fe3+ using photoinduced green synthesized AgNPs. For the synthesis purpose, an aqueous extract of Croton bonplandianum (AEC) was used as a reducing and stabilizing agent. The biosynthesis was confirmed by UV-visible spectroscopy where an SPR band at λmax 436nm after 40s and 428nm after 30min corresponded to the existence of AgNPs. The optimum conditions for biosynthesis of AgNPs were 30min sunlight exposure time, 5.0% (v/v) AEC inoculum dose and 4mM AgNO3 concentration. The stability of synthesized AgNPs was monitored up to 9months. The size and shape of AgNPs with average size 19.4nm were determined by Field Emission Scanning Electron Microscope (FE-SEM) and High-Resolution Transmission Electron Microscope (HR-TEM). The crystallinity was determined by High-Resolution X-ray Diffractometer (HR-XRD) and Selected Area Electron Diffraction (SAED) pattern. The chemical and elemental compositions were determined by Fourier Transformed Infrared Spectroscopy (FTIR) and Energy Dispersive X-ray Spectroscopy (EDX) respectively. The Atomic Force Microscopy (AFM) images represented the lateral and 3D topological characteristics of AgNPs. The XPS analysis confirmed the presence of two individual peaks which attributed to the Ag 3d3/2 and Ag 3d5/2 binding energies corresponding to the presence of metallic silver. The biosynthesized AgNPs showed potent antibacterial activity against both gram-positive and gram-negative bacterial strains as well as antioxidant activity. On the basis of results and facts, a probable mechanism was also proposed to explore the possible route of AgNPs synthesis, colorimetric detection of Fe3+, antibacterial and antioxidant activity.

Kinetic, isotherm and thermodynamic studies of adsorption behaviour of CNT/CuO nanocomposite for the removal of As(III) and As(V) from water

A CNT/CuO nanocomposite prepared by precipitation method was characterized through FT-IR, XRD, SEM, TGA, BET and Raman spectroscopy and utilized as a nanoadsorbent for the adsorption of As(III)/As(V) from water where maximum uptake capacities of 2267 μg g−1 for As(III) and 2395 μg g−1 for As(V) were achieved. This CNT/CuO nanocomposite is a better alternative to known conventional adsorbents because it has a high surface area (480 m2 g−1) and maximum uptake capacities were achieved at ambient temperature (30 °C) and near neutral pH (pH 7 for As(III) and 5 for As(V)). Kinetic studies indicated that a pseudo-second-order kinetic model described the kinetic data. The mass transfer and intraparticle diffusion studies suggested that both external mass transfer and intraparticle diffusion steps contributed to the rate controlling step. The Boyd model suggested that intraparticle diffusion was the main rate controlling step. Isotherm studies were conducted and it was found that the equilibrium data followed the Langmuir isotherm which indicated that the adsorption was a monolayer and all the binding sites were energetically equivalent. The D–R isotherm revealed that the adsorption was chemisorption. The thermodynamic studies revealed that the adsorption was spontaneous because ΔG0 was negative and the reaction was endothermic due to the positive value of ΔH0. XPS analysis revealed that CNT/CuO not only adsorbed As(III)/As(V) but also oxidized highly toxic As(III) to less toxic As(V) which is an added advantage of CNT/CuO as an adsorbent.