Adsorption and dehydrogenation of ammonia on Ru55, Cu55 and Ru@Cu54 nanoclusters: role of single atom alloy catalyst.

Hydrogen production by the catalytic decomposition of ammonia (NH3) is an important process for several important applications, which include energy production and environment-related issues. The role of single Ru-atom substitution in a Cu55 nanocluster (NC) has been illustrated using the NH3 decomposition reaction as a model system. The structural stability of Ru@Cu54 NC has been evaluated using Ru55 and Cu55 NCs for comparison. Ru@Cu54 prefers an icosahedron structure (Ih), like Ru55 and Cu55 NCs, with almost comparable average binding energies of -5.55 eV per atom. The adsorption of NHx (x = 0-3) on different adsorption sites of the icosahedron Ru@Cu54 NC has also been studied and the corresponding adsorption energies have been estimated. The site-preference investigation suggested that NH3 prefers to adsorb vertically to the Ru@Cu54. The stable geometries of the N and H atoms on the high symmetry adsorption sites of Ru@Cu54 NC have been studied. Although the N atom favours top and hollow sites, the H atom prefers to stay in the Ru-Cu bridge site along with the hollow sites. The adsorption energy of N on the Ru@Cu54 NC fcc site is found to be -5.42 eV, which is very close to the optimal value (-5.81 eV) of the ammonia decomposition volcano curve. The reaction energies for stepwise H atom elimination from an adsorbed NH3 molecule have been estimated. Finally, NH3 adsorption and decomposition on Ru@Cu54 have been illustrated in terms of electronic structure analysis. The energetics calculations for the dehydrogenation of NH3 suggest that Ru@Cu54 NC can be a suitable catalyst.

CO2 hydrogenation to formic acid on Pd-Cu nanoclusters: a DFT study.

Carbon dioxide (CO2) hydrogenation to formic acid is a promising method for the conversion of CO2 to useful organic products. The interaction of CO2 with hydrogen (H2) on PdmCun (m + n = 4, 8 and 13) clusters to form formic acid (HCOOH) has been explored using density functional theoretical (DFT) calculations. Pd2Cu2, Pd4Cu4 and 13-atom Pd12Cu clusters are found to be the most stable among all of the PdmCun (m + n = 4, 8 and 13) clusters with binding energies of -1.75, -2.16 and -2.40 eV per atom, respectively. CO2 molecules get adsorbed on the Pd2Cu2, Pd4Cu4 and Pd12Cu clusters in an inverted V-shaped way with adsorption energies of -0.91, -0.96 and -0.44 eV, respectively. The hydrogenation of CO2 to form formate goes through a unidentate structure that rapidly transforms into the bidentate structure. To determine the transition state structures and minimum energy paths (MEPs) for CO2 hydrogenation to formic acid, the climbing image nudge elastic band (CI-NEB) method has been adopted. The activation barriers for the formation of formic acid from formate on Pd2Cu2 and Pd4Cu4 are calculated to be 0.79 and 0.68 eV, respectively whereas that on the Pd12Cu cluster is 1.77 eV. The enthalpy for the overall process of CO2 hydrogenation to formic acid on the Pd2Cu2, Pd4Cu4 and Pd12Cu clusters are found to be 0.83, 0.48 and 0.63 eV, respectively. Analysis of the density of states (DOS) spectra show that the 4d orbital of Pd, the 3d orbital of Cu, and the 2p orbitals of C and O atoms are involved in the bonding between CO2 molecules and the Pd2Cu2 clusters. The CO2 adsorption on the PdmCun (m + n = 4 and 8) clusters has also been explained in terms of the charge density distribution analysis.

Why Do Relative Intensities of Charge Transfer and Intra-4f Transitions of Eu3+ Ion Invert in Yttrium Germanate Hosts? Unravelling the Underlying Intricacies from Experimental and Theoretical Investigations.

The dominant intensity of parity-forbidden intra-4f transitions of europium(III) over O → Eu charge-transfer band (CTB) intensity is against common perceptions, yet this trend is observed in many germanate hosts and has not been rationalized so far. In search of a plausible explanation for this unusual trend, present work reports an experimental and theoretical investigations in conjunction on two sibling germanate host, namely, Y2GeO5 and Y2Ge2O7 having dopant Eu3+ in their respective YO7 polyhedra. Whereas for Y2GeO5:Eu3+, the CTB is more intense than the intra-4f transitions in the excitation spectrum, in the case of Y2Ge2O7:Eu3+, the relative intensities of CTB and intra-4f transitions are reversed. Comparative structural analysis reveals that Eu3+ present in YO7 of Y2GeO5 has a greater number of tetra-coordinated oxygen (Otetra) and yttrium atom as first and second neighbors, respectively (Eu3+-Otetra-Y3+ linkages). Conversely, in Y2Ge2O7 host, the Eu3+ ion mostly has tricoordinated oxygen (Otri) as its nearest neighbor and germanium ions next to Otri (Eu3+-Otri-Ge4+ linkage). Theoretical calculations reveal that while Y2GeO5:Eu has Otetra(4Y) dominating at the Fermi level and the 4f state of Eu3+ remains inert toward mixing, in Y2Ge2O7:Eu, the Fermi level has major contribution from Otri(2Y + 1Ge) with significant mixing with 4f states of Eu. The dominant control of Eu3+-Otri-Ge4+ linkages in geometrical and electronic structure of Y2Ge2O7:Eu owing to the GeO4 surrounding has been attributed to relative poor intensity of O → Eu CTB. Siege of Eu3+ by GeO4 and subsequent occurrence of Eu3+-Otri-Ge4+ linkages play a dual role: First, it induces electronic rigidity to hinder excitation of electron at bridging (Otri) oxygen by highly charged small Ge4+ cation; second, the covalent character in Eu-O bond is achieved by intermixing of Eu's 4f and Otri 2p orbital which facilitates relaxing of the parity-selection rule thus enhancing the probability of intra-4f transitions. The inferences drawn remain valid when extrapolated to other inorganic oxides having EuOx polyhedra surrounded by covalent units like PO4, SiO4, etc. and have a prevailing number of low-coordinated oxygen atoms and highly charged small cation in the first and second coordination shells, respectively. The optical basicity concept is also found to endorse our explanation. These remarkable generic inferences will pave the rational way for designing efficient phosphors for solid-state lighting.

Does the chromagen blue filter lens affect the reading speed, accuracy and contrast sensitivity.

PURPOSE: To determine the effects of ChromaGen blue filter lens in reading speed, accuracy and contrast sensitivity. METHODS: A cross-over, randomised study was carried out on 40 individuals (11 males and 29 females) aged 21 to 30 years. The rate of reading and reading accuracy was calculated with and without ChromaGen blue filter lens in all subjects. Wilkins Rate of Reading Test was used to measure the rate of reading and reading accuracy. Contrast sensitivity was also evaluated by using with and without the ChromaGen blue filter lens. RESULTS: The mean rate of reading with and without ChromaGen blue filter lens was 160.58±16.03 words per minute and 150.52±15.66 words per minute respectively, with significant difference of p<0.001. The mean of reading accuracy (words correctly read per minute) in subjects, with ChromaGen blue filter was 149.30±0.79 words and without using filter lens was 148.53±1.11 words and found to be significant (p<0.001). There was no significant difference in the contrast sensitivity between subjects with and without the ChromaGen blue filter lens (p=0.083). No significant correlation was noted between the reading speed with age, spherical equivalent, contrast sensitivity, and reading accuracy. CONCLUSION: This study concludes that there was an increase of 6.68% in the rate of reading and improvement of 0.52% in accuracy among subjects with ChromaGen blue filter lens.

Pretreated algal bloom as a substantial nutrient source for microalgae cultivation for biodiesel production.

In the present investigation, toxic algal bloom, a copious and low-cost nutrient source was deployed for cultivating Chlorella pyrenoidosa. Various pre-treatment methods using combinations of acid/alkali and autoclave/microwave were tested for preparing hydrolysates and compared with minimal media (BG-11). Acid autoclave treatment resulted in maximum carbon, nitrogen and phosphorous content which substantially boosted the growth of the microalgal cells (4.36g/L) as compared to rest of the media. The microalga grown in this media also showed enhanced lipid content (43.2%) and lipid productivity (188mg/L/d) as compared to BG-11 (19.42mg/L/d). The biochemical composition showed 1.6-fold declines in protein while 1.27 folds in carbohydrate content as compared to BG-11. The fatty acid profile revealed the presence of C14-C22 with increased amount of monounsaturated fatty acids as compared to BG-11. The results obtained showed that algal bloom can be used as a potential nutrient source for microalgae.

Toxicity and bioremediation of As(III) and As(V) in the green microalgae Botryococcus braunii: A laboratory study.

Worldwide threats of fuel shortages in the near future and climate change because of greenhouse gas emissions are posing severe challenges and therefore it is vital to search for sustainable ways of preventing the consequences. The dual use of microalgae for phycoremediation and biomass production for sustainable biofuel production is a viable choice. Phycoremediation of As(III) and As(V) ions using microalgae was investigated in a two-staged batch reactor. Accumulation and toxicity of inorganic arsenic forms (As(III) and As(V)) to green microalgae Botryococcus braunii depend on environmental factors. Dissolved oxygen and pH cycles did not significantly differ due to the absence or presence of arsenic (either As(III) or As(V)) ions in the culture. Monod model was utilized for representing the growth kinetics of microalgae in pure media containing various concentrations of nitrate ions. Maximum specific growth rate and saturation constant were found to be 0.14788 d-1 and 0.00105 g/L, respectively. With the increase in concentration of phosphate in growth medium, the growth of microalgae increased. Media with NaCl (1.0 g/L) and NaHCO3 (1 g/L) resulted in higher maximum biomass concentration. Effect of coexisting ions on phycoremediation of As(III) and As(V) ions using microalgae was studied.

Sequestering of As(III) and As(V) from wastewater using a novel neem leaves/MnFe2O4 composite biosorbent.

An arsenic biosorbent comprising neem leaves (NL) and MnFe2O4 particles was developed and its removal potential was investigated. Physicochemical analysis of the NL/MnFe2O4 composite (MNL) was performed for the Brunauer, Emmett and Teller surface area, Fourier transform infrared spectra (FT-IR), and scanning electron microscopy-Energy-dispersive X-ray (EDX). The following parameters were optimized: pH, biosorbent dose, contact time, temperature, and initial arsenic concentration. The optimum pH values achieved for biosorption of As(III) and As(V) were 7.0 and 4.0, respectively, when the equilibrium time was 110 minutes for both. MNL was found to be efficient with 85.217% and 88.154% biosorption efficiency at a concentration of 50 mg/L of As(III) or As(V) solution, respectively. This was also proved by the FT-IR study of arsenic-loaded biosorbent. For establishing the best suitable correlation for the equilibrium curves exploiting the procedure of the nonlinear regression for curve fitting analysis, isotherm studies were conducted for As(III) and As(V) using 30 isotherm models. The pattern of biosorption fitted well with Brouers-Sotolongo isotherm model for As(III) and Langmuir-Freundlich as well as Sips isotherm models for As(V). Dubinin-Radushkevich (D-R) isotherm studies specified that ion exchange might play a significant role. The influence of various co-existing ions at different concentrations was examined. Desorption study was performed using various concentrations of NaOH solution.

Corynebacterium glutamicum MTCC 2745 immobilized on granular activated carbon/MnFe2O4 composite: A novel biosorbent for removal of As(III) and As(V) ions.

The optimization of biosorption/bioaccumulation process of both As(III) and As(V) has been investigated by using the biosorbent; biofilm of Corynebacterium glutamicum MTCC 2745 supported on granular activated carbon/MnFe2O4 composite (MGAC). The presence of functional groups on the cell wall surface of the biomass that may interact with the metal ions was proved by FT-IR. To determine the most appropriate correlation for the equilibrium curves employing the procedure of the non-linear regression for curve fitting analysis, isotherm studies were performed for As(III) and As(V) using 30 isotherm models. The pattern of biosorption/bioaccumulation fitted well with Vieth-Sladek isotherm model for As(III) and Brouers-Sotolongo and Fritz-Schlunder-V isotherm models for As(V). The maximum biosorption/bioaccumulation capacity estimated using Langmuir model were 2584.668mg/g for As(III) and 2651.675mg/g for As(V) at 30°C temperature and 220min contact time. The results showed that As(III) and As(V) removal was strongly pH-dependent with an optimum pH value of 7.0. D-R isotherm studies specified that ion exchange might play a prominent role.

The use of artificial neural network for modelling of phycoremediation of toxic elements As(III) and As(V) from wastewater using Botryococcus braunii.

In the present study, a thorough investigation has been done on the removal efficiency of both As(III) and As (V) from synthetic wastewater by phycoremediation of Botryococcus braunii algal biomass. Artificial neural networks (ANNs) are practised for predicting % phycoremediation efficiency of both As(III) and As(V) ions. The influence of several parameters for example initial pH, inoculum size, contact time and initial arsenic concentration (either As(III) or As(V)) was examined systematically. The maximum phycoremediation of As(III) and As(V) was found to be 85.22% and 88.15% at pH9.0, equilibrium time of 144h by using algal inoculum size of 10% (v/v) and initial arsenic concentration of 50mg/L. The data acquired from laboratory scale experimental set up was utilized for training a three-layer feed-forward back propagation (BP) with Levenberg-Marquardt (LM) training algorithm having 4:5:1 architecture. A comparison between the experimental data and model outputs provided a high correlation coefficient (R(2)all_ANN equal to 0.9998) and exhibited that the model was capable for predicting the phycoremediation of both As(III) and As(V) from wastewater. The network topology was optimized by changing number of neurons in hidden layers. ANNs are efficient to model and simulate highly non-liner multivariable relationships. Absolute error and Standard deviation (SD) with respect to experimental output were calculated for ANN model outputs. The comparison of phycoremediation efficiencies of both As(III) and As(V) between experimental results and ANN model outputs exhibited that ANN model can determine the behaviour of As(III) and As(V) elimination process under various circumstances.

Application of granular activated carbon/MnFe2O4 composite immobilized on C. glutamicum MTCC 2745 to remove As(III) and As(V): Kinetic, mechanistic and thermodynamic studies.

The main objective of the present study was to investigate the efficiency of Corynebacterium glutamicum MTCC 2745 immobilized on granular activated carbon/MnFe2O4 (GAC/MnFe2O4) composite to treat high concentration of arsenic bearing wastewater. Non-linear regression analysis was done for determining the best-fit kinetic model on the basis of three correlation coefficients and three error functions and also for predicting the parameters involved in kinetic models. The results showed that Fractal-like mixed 1,2 order model for As(III) and Brouser-Weron-Sototlongo as well as Fractal-like pseudo second order models for As(V) were proficient to provide realistic description of biosorption/bioaccumulation kinetic. Applicability of mechanistic models in the current study exhibited that the rate governing step in biosorption/bioaccumulation of both As(III) and As(V) was film diffusion rather than intraparticle diffusion. The evaluated thermodynamic parameters ΔG(0), ΔH(0) and ΔS(0) revealed that biosorption/bioaccumulation of both As(III) and As(V) was feasible, spontaneous and exothermic under studied conditions.

Modulation of band gap by an applied electric field in silicene-based hetero-bilayers.

Electronic properties of the hetero-structures consisting of silicene, graphene and BN monolayers under the influence of an electric field were investigated using density functional theory. With no electric field, both silicene/graphene and silicene/BN were shown to have a finite gap of about ∼50 meV, though silicene is a zero-gap two-dimensional material. Application of the field perpendicular to the bilayer system was found to facilitate modulation of the band gap, exhibiting an approximately linear relationship with the gap energy, in contrast to what was seen for the constituent monolayers. Also, the degree of the modulation was mainly determined by the Si-pz electronic states at the interface of the silicene/graphene and silicene/BN bilayers.

h-BN monolayer on the Ni(111) surface: a potential catalyst for oxidation.

The hexagonal boron nitride (h-BN) is traditionally considered to be inert. In sharp contrast to the inert behavior of free-standing hexagonal boron nitride (h-BN), we propose the catalytic property of h-BN monolayer on Ni(111) substrate using first-principles density functional theory investigation. The interaction of O2 molecule with the h-BN/Ni(111) substrate results in nondissociative adsorption of the molecule along with elongation of the O-O bond. This can be considered as the activated state of the O2 molecule. Further interaction of this complex viz O2-h-BN/Ni(111) with an incoming CO molecule leads to the spontaneous formation of CO2. Interestingly, the CO adsorption on the h-BN/Ni(111) substrate was found to be unfavorable, thereby implying the oxidation of CO selectively through Eley-Rideal (ER) mechanism.

Kinetics studies of p-cresol biodegradation by using Pseudomonas putida in batch reactor and in continuous bioreactor packed with calcium alginate beads.

Present study deals with the biodegradation of p-cresol by using Pseudomonas putida in a batch reactor and a continuous bioreactor packed with calcium alginate beads. The maximum specific growth rate of 0.8121 h(-1) was obtained at 200 mg L(-1) concentration of p-cresol in batch reactor. The maximum p-cresol degradation rate was obtained 6.598 mg L(-1) h(-1) at S(o)=200 mg L(-1) and 62.8 mg L(-1) h(-1) at S(o)=500 mg L(-1) for batch reactor and a continuous bioreactor, respectively. The p-cresol degradation rate of continuous bioreactor was 9 to 10-fold higher than those of the batch reactor. It shows that the continuous bioreactor could tolerate a higher concentration of p-cresol. A Haldane model was also used for p-cresol inhibition in batch reactor and a modified equation similar to Haldane model for continuous bioreactor. The Haldane parameters were obtained as µ(max) 0.3398 h(-1), K(s) 110.9574 mg L(-1), and K(I) 497.6169 mg L(-1) in batch reactor. The parameters used in continuous bioreactor were obtained as D(max) 91.801 mg L(-1) h(-1), K(s) 131.292 mg L(-1), and K(I) 1217.7 mg L(-1). The value K(I) of continuous bioreactor is approximately 2.5 times higher than the batch reactor. Higher K(I) value of continuous bioreactor indicates P. putida can grow at high range of p-cresol concentration. The ability of tolerance of higher p-cresol concentrations may be one reason for biofilm attachment on the packed bed in the continuous operation.

Biodegradation of mono-chlorobenzene by using a trickle bed air biofilter (TBAB).

In the present study, performance of the trickle bed airbiofilter (TBAB) for treating mono-chlorobenzene (MCB) was evaluated for various influent volatile organic compound (VOC) loadings using coal and mixed consortium of activated sludge as the packing material. Microbial acclimation to MCB was achieved by exposing the system continuously for 31 d to an average inlet MCB concentration of 0.688 g m(-3) at an empty bed residence time (EBRT) of 188 s. The TBAB achieved maximum removal efficiency of 87% at an EBRT of 188 s for an inlet concentration of 0.681 g m(-3), which is quite significance than the values reported in the literature. Elimination capacities of MCB increased with an increase of the influent VOC loading, but an opposite trend was observed for the removal efficiency The maximum elimination capacity of the biofilter was 110.75 g m(-3) hr(-1) at an inlet MCB concentration of 1.47 g m(-3). The effect of starvation on the TBAB was also studied. After starvation, the TBAB lost its ability to degrade MCB initially However the biofilter recovered very quickly Evaluation of the concentration profile along the bed height indicated that the bottom section of TBAB has the best performance for all concentrations. By using Wani's method of macrokinetic determination based on simple Monod kinetics, the maximum removal rate of MCB, r(max) and saturation constant K(m) was to be found as 1.304 g m(-3)s(-1) and 113.446 g m(-3), respectively.

First-principles study of the H(2) interaction with transition metal (Ti, V, Ni) doped Mg(0001) surface: Implications for H-storage materials.

Using first-principles calculations we have investigated the interaction of hydrogen molecules with clean and M (Ti, V, and Ni) doped Mg(0001) surfaces. The calculations have been carried out using plane-wave-based pseudopotential method under the formalism of density functional theory. First we have calculated the stability of the M atoms on the Mg surface. On the basis of the energetic criteria, we found that all these M atoms prefer to substitute one of the Mg atoms from the second layer than the top surface atom. In the second step we have studied the interaction of a hydrogen molecule with the clean and doped Mg surface. The results show that for M atoms at the surface, the hydrogen molecule undergoes spontaneous dissociative chemisorptions. However, for M atoms in the second layer, it requires to cross an activation barrier to undergo molecular dissociation. Furthermore, to understand the mobility of hydrogen atoms on the surface we have calculated the diffusion energy barriers for the M doped surface. Contrary to the molecular dissociation behavior, it is found that the mobility of hydrogen atoms on the surface is easier if the M atoms are placed in the second layer in comparison to that in the top surface layer. It is believed that the results of the present study provide useful information based on the first-principles calculations for synthesizing Mg based materials for hydrogen storage with optimal performance.

Growth of three bacteria in arsenic solution and their application for arsenic removal from wastewater.

The present paper compares the arsenic removal capacities of three bacterial strains namely, Ralstonia eutropha MTCC 2487, Pseudomonas putida MTCC 1194 and Bacillus indicus MTCC 4374 form wastewater (simulated acid mine drainage) containing arsenic (As(III):As(V)::1:1), Fe, Mn, Cu and Zn in the concentration of 15 mg/l, 10 mg/l, 2 mg/l, 5 mg/l and 10 mg/l respectively, in bulk liquid phase. Growth patterns of these bacteria in presence of arsenic in solution as well as under starvation have also been investigated as the acid mine drainage normally does not contain organic carbon and also contains high arsenic. At the nutrient broth concentration of 1.25 g/l and in presence of 15 mg/l arsenic sufficient growth of these strains have been observed. However, growth of Ralstonia eutropha MTCC 2487 has been found slightly more than Pseudomonas putida MTCC 1194 and Bacillus indicus MTCC 4374. Arsenic removal capacities of Ralstonia eutropha MTCC 2487, Pseudomonas putida MTCC 1194 and Bacillus indicus MTCC 4374 from simulated acid mine drainage are approximately 67%, 60% and 61% respectively. It has also been observed that arsenic concentration of 15 mg/l prolongs the stationary phase of these strains. pH and temperature for the above studies have been maintained at 7.1 +/- 0.1 and 29 +/- 1 degrees C, respectively.

Biodegradation of pyridine by the new bacterial isolates S. putrefaciens and B. sphaericus.

In this study, two bacterial strains capable of utilizing pyridine as a sole carbon source were isolated from biofilters. Based on the biochemical test, the organisms were identified as Shewanella putrefaciens and Bacillus sphaericus. In liquid cultures, S. putrefaciens and B. sphaericus degraded pyridine quite effectively up to 500 mg L(-1). S. putrefaciens degrades 500 mg L(-1) of pyridine completely within 140 h, whereas the B. sphaericus degrades 500 mg L(-1) of pyridine only nearly 75% and takes a longer duration of 150 h. S. putrefaciens used pyridine as sole carbon and energy source better than B. sphaericus. Monod's and Haldane's inhibitory growth models were used to obtain maximum specific growth rate (micro(max)), half saturation (K(s)) and substrate inhibition (K(i)) constant for pyridine by using S. putrefaciens and B. sphaericus. The high value of K(i) for S. putrefaciens than B. sphaericus indicates that the inhibition effect can be observed only in a high concentration range. The S. putrefaciens degrades pyridine with a faster rate than B. sphaericus. S. putrefaciens can be used effectively for the treatment of pyridine bearing wastewater and as an inoculum in a biofilter treating pyridine-laden gas.

Novel biofiltration methods for the treatment of heavy metals from industrial wastewater.

Most heavy metals are well-known toxic and carcinogenic agents and when discharged into the wastewater represent a serious threat to the human population and the fauna and flora of the receiving water bodies. In the present review paper, the sources have discussed the industrial source of heavy metals contamination in water, their toxic effects on the fauna and flora and the regulatory threshold limits of these heavy metals. The various parameters of the biofiltration processes, their mechanism for heavy metals removal along with the kinetics of biofilters and its modeling aspects have been discussed. The comparison of various physico-chemical treatment and the advantages of biofiltration over other conventional processes for treatment of heavy metals contaminated wastewater have also been discussed. The applications of genetic engineering in the modification of the microorganisms for increasing the efficiency of the biofiltration process for heavy metals removal have been critically analyzed. The results show that the efficiency of the process can be increased three to six folds with the application of recombinant microbial treatment.

Treatment of arsenic contaminated water in a batch reactor by using Ralstonia eutropha MTCC 2487 and granular activated carbon.

This paper presents the observations on the bio-removal of arsenic from contaminated water by using Ralstonia eutropha MTCC 2487 and activated carbon in a batch reactor. The effects of agitation time, pH, type of granular activated carbon (GAC) and initial arsenic concentration (As(o)) on the % removal of arsenic have been discussed. Under the experimental conditions, optimum removal was obtained at the pH of 6-7 with agitation time of 100 h. The % removal of As(T) increased initially with the increase in As(o) and after attaining the maximum removal (~86%) at the As(o) value of around 15 ppm, it started to decrease. Simultaneous adsorption bioaccumulation (SABA) was observed, when fresh GAC was used as supporting media for bacterial immobilization. In case of SABA, the % removal of As(III) was almost similar (only ~1% more) to the additive values of individual removal of As(III) obtained by only adsorption and only bio-adsorption. However, for As(V) the % removal was less (~8%) than the additive value of the individual % removals obtained by only adsorption and bio-adsorption. Percentage removal of Fe, Mn, Cu and Zn were 65.17%, 72.76%, 98.6% and 99.31%, respectively. Maximum regeneration (~99.4%) of the used bio-adsorbent was achieved by the treatment with 5NH(2)SO(4) followed by 1N NaOH and 30% H(2)O(2) in HNO(3). The fitness of the isotherms to predict the specific uptake for bio-adsorption/accumulation process has been found to decrease in the following order: Temkin isotherm>Langmuir isotherm>Freundlich isotherm. For the adsorption process with fresh GAC the corresponding order is Freundlich isotherm>Langmuir isotherm>Temkin isotherm for As(V) and As(T). However, for As(III) it was Langmuir>Temkin>Freundlich.

Biofiltration and kinetic aspects of a biotrickling filter for the removal of paint solvent mixture laden air stream.

In the present study, removal of methyl ethyl ketone (MEK), toluene, n-butyl acetate and o-xylene (MTBX) emitted from the paint industry was carried out in a coal based biotrickling filter. When the influent MTBX loadings were less than 120 gm(-3)h(-1), nearly 100% removal could be achieved. A maximum elimination capacity of 184.86 gm(-3)h(-1) was obtained at a MTBX load of 278.27 gm(-3)h(-1) with an empty bed residence time of 42.4s in phase V. Results showed that the condition was the most favorable for n-butyl acetate degradation followed by MEK, toluene and then o-xylene. The corresponding maximum removal rate, r(max) values of MTBX were calculated as 0.085, 0.033, 0.16 and 0.024 gm(-3)h(-1), respectively. Standard deviation of error in prediction of MEK, toluene and o-xylene removal were within limit of 10%, while in the case of n-butyl acetate this was approximately 60%. The MTBX concentration profiles along the depth were also determined by using convection-diffusion reaction (CDR) model. It was observed that at low concentration and low flow rate, the model is in good agreement with the experimental values for MEK, toluene and n-butyl acetate, but for o-xylene the model results deviated from the experimental.