The present study synthesized nano-magnetite (Fe3O4) from milled steel chips using the high energy ball milling (HEBM) method, characterized it, and then utilized it as a sorbent to remediate boron concentration at various pH (4-9), dosages (0.1-0.5 g), contact times (20-240 min), and initial concentrations (10-100 mg/L). The nano-sorbents were characterized based on SEM structure, elemental composition (EDX), surface area analysis (BET), crystallinity (XRD), and functional group analysis (FTIR). The highest adsorption capacity of 8.44 mg/g with removal efficiency of 84% was attained at pH 8, 0.5 g dosage, contact time of 180 min, and 50 mg/L initial concentration. The experimental data fit best with the pseudo-second-order kinetic model with R2 of 0.998, while the Freundlich adsorption isotherm describes the adsorption process with an R2 value of 0.9464. A regeneration efficiency of 47% was attained even after five cycles of reusability studies. This efficiency implies that the nano-magnetite has the potential for sustainable industrial application.
In developing countries like India, an economically viable and ecologically approachable strategy is required to safeguard the drinking water. Excessive fluoride intake through drinking water can lead to dental fluorosis, skeletal fluorosis, or both. The present study has been under with an objective to investigate the feasibility of using cellulose derived from coconut fiber as an adsorbent under varying pH conditions for fluoride elimination from water. The assessment of equilibrium concentration of metal ions using adsorption isotherms is an integral part of the study. This present finding indicates the considerable effect of variation of adsorbent dosages on the fluoride removal efficiency under constant temperature conditions of 25 ± 2 °C with a contact period of 24 h. It is pertinent to mention that maximum adsorption of 88% has been observed with a pH value of 6 with 6 h time duration with fluoride dosage of 50 mg/L. The equilibrium concentration dwindled to 0.4 mg/L at fluoride concentration of 20 mg/L. The Langmuir model designates the adsorption capacity value of 2.15 mg/L with initial fluoride concentration of 0.21 mg/g with R2 value of 0.660. Similarly, the adsorption capacity using Freundlich isotherms is found to be 0.58 L/g and 0.59 L/g with fluoride concentration of 1.84 mg/L and 2.15 mg/L respectively. The results from the present study confirm that coconut fiber possesses appropriate sorption capabilities of fluoride ion but is a pH dependent phenomenon. The outcomes of the study indicate the possible use of cellulose extracted from waste coconut fiber as a low-cost fluoride adsorbent. The present study can be well implemented on real scale systems as it will be beneficial economically as well as environmentally.
The present study investigated the biosorption capacity of live and dead cells of a novel Bacillus strain for chromium. The optimum biosorption condition was evaluated in various analytical parameters, including initial concentration of chromium, pH, and contact time. The Langmuir isotherm model showed an enhanced fit to the equilibrium data. Live and dead biomasses followed the monolayer biosorption of the active surface sites. The maximum biosorption capacity was 20.35 mg/g at 25 °C, with pH 3 and contact time of 50 min. Strain 139SI was an excellent host to the hexavalent chromium. The biosorption kinetics of chromium in the dead and live cells of Bacillus salmalaya (B. salmalaya) 139SI followed the pseudo second-order mechanism. Scanning electron microscopy and fourier transform infrared indicated significant influence of the dead cells on the biosorption of chromium based on cell morphological changes. Approximately 92% and 70% desorption efficiencies were achieved using dead and live cells, respectively. These findings demonstrated the high sorption capacity of dead biomasses of B. salmalaya 139SI in the biosorption process. Thermodynamic evaluation (ΔG⁰, ΔH⁰, and ΔS⁰) indicated that the mechanism of Cr(VI) adsorption is endothermic; that is, chemisorption. Results indicated that chromium accumulation occurred in the cell wall of B. salmalaya 139SI rather than intracellular accumulation.
The thermoluminescence (TL) glow curves and kinetics parameters of Thulium (Tm) doped silica cylindrical fibers (CF) are presented. A linear accelerator (LINAC) was used to deliver high-energy radiation of 21MeV electrons and 10MV photons. The CFs were irradiated in the dose range of 0.2-10Gy. The experimental glow curve data was reconstructed by using WinREMS. The WinGCF software was used for the kinetic parameters evaluation. The TL sensitivity of Tm-doped silica CF is about 2 times higher as compared to pure silica CF. Tm-doped silica CF seems to be more sensitive to 21MeV electrons than to 10MV photons. Surprisingly, no supralinearity was displayed and a sub-linear response of Tm-doped silica CF was observed within the analyzed dose range for both 21MeV electrons and 10MV photons. The Tm-doped silica CF glow curve consists of 5 individual glow peaks. The Ea of peak 4 and peak 5 was highly dependent on dose when irradiated with photons. We also noticed that the electron radiation (21MeV) caused a shift of glow peak by 7-13°C to the higher temperature region compared with photons radiation (10MV). Our Tm-doped fibers seem to give high TL response after 21MeV electrons, which gives around 2 times higher peak integral as compared with 10MV photon radiation. We concluded that peak 4 is the first-order kinetic peak and can be used as the main dosimetric peak of Tm-doped silica CF.
Microbial conversion of syngas to energy-dense biofuels and valuable chemicals is a potential technology for the efficient utilization of fossils (e.g., coal) and renewable resources (e.g., lignocellulosic biomass) in an environmentally friendly manner. However, gas-liquid mass transfer and kinetic limitations are still major constraints that limit the widespread adoption and successful commercialization of the technology. This review paper provides rationales for syngas bioconversion and summarizes the reaction limited conditions along with the possible strategies to overcome these challenges. Mass transfer and economic performances of various reactor configurations are compared, and an ideal case for optimum bioreactor operation is presented. Overall, the challenges with the bioprocessing steps are highlighted, and potential solutions are suggested. Future research directions are provided and a conceptual design for a membrane-based syngas biorefinery is proposed.
Lithium potassium borate (LKB) glasses co-doped with TiO2 and MgO were prepared using the melt quenching technique. The glasses were cut into transparent chips and exposed to gamma rays of (60)Co to study their thermoluminescence (TL) properties. The TL glow curve of the Ti-doped material featured a single prominent peak at 230 °C. Additional incorporation of MgO as a co-activator enhanced the TL intensity threefold. LKB:Ti,Mg is a low-Z material (Z(eff)=8.89) with slow signal fading. Its radiation sensitivity is 12 times lower that the sensitivity of TLD-100. The dose response is linear at doses up to 10(3) Gy. The trap parameters, such as the kinetics order, activation energy, and frequency factor, which are related to the glow peak, were determined using TolAnal software.
Preserved human amniotic membrane either air dried or glycerol preserved has been used effectively to treat superficial and partial thickness wounds without leaving any obvious hypertrophic scar. The preserved amnion, sterilised by ionising radiation, is known as an effective barrier for heat, fluid and protein loss while adheres nicely on wound. Air drying slightly reduced the oxygen transmission rate (OTR) of the amnion and the value significantly dropped after 15 kGy (p < 0.05). Glycerol preservation significantly reduced (p < 0.05) the OTR indicating less oxygen transmitted through the well structured cells of the amnion. Increase in the OTR with the increasing radiation doses up to 35 kGy possibly due to direct effects of radiation that resulted in large intercellular gaps. Both preservation methods significantly increased (p < 0.05) the water vapour transmission rate (WVTR). However, the low WVTR in the air dried amnion at 15 and 25 kGy was postulated due to cross-linking of collagen. Changes in the biophysical properties can be linked to direct and indirect effects of radiation on collagen bundles. The radiation dose of 25 kGy caused no adverse effect on biophysical properties hence it is still acceptable to sterilize both the air dried and the glycerol preserved amnions.
The values of pseudo-first-order rate constants (k(obs)) for alkaline hydrolysis of 1, obtained at 1.0 mM NaOH and within [C(m)E(n)]T (total concentration of C(m)E(n)) range of 3.0-5.0 mM for C(12)E(23) and 10-20 mM for C(18)E(20), fail to obey pseudophase micellar (PM) model. The values of the fraction of near irreversible C m E n micellar trapped 1 molecules (F(IT1)) vary in the range ~0-0.75 for C(12)E(23) and ~0-0.83 for C(18)E(20) under such conditions. The values of F(IT1) become 1.0 at ≥ 10 mM C(12)E(23) and 50 mM C(18)E(20). Kinetic analysis of the observed data at ≥ 10 mM C(12)E(23) shows near irreversible micellar entrapment of 1 molecules under such conditions.
This study was conducted to evaluate the kinetic characteristics of proteolytic activity of proteases on Channa striatus protein fractions. Degree of hydrolysis (DH), amino acid composition and kinetic parameters of sarcoplasmic and myofibrillar proteins were investigated when incubated with proteinase K and thermolysin, separately. After 30 min incubation with proteases, a decrease in DH of sarcoplasmic protein was observed whereas, hydrolysis of myofibrillar protein with proteases took 2 h with an increase in DH. The major amino acids were glutamic acid (16.6%) in thermolysin- myofibrillar hydrolysate followed by aspartic acid (11.1%) in sarcoplasmic protein fraction with no enzyme treatment and lysine (10%) in thermolysin-myofibrillar hydrolysate. The apparent Michaelis constant of proteinase K was lower than thermolysin for both sarcoplasmic and myofibrillar proteins. However, rate of turnover and enzyme efficiency suggested that sarcoplasmic and myofibrillar proteins are suitable substrates for proteinase K and thermolysin hydrolytic reaction, respectively.
Closed form solutions for unsteady free convection flows of a second grade fluid near an isothermal vertical plate oscillating in its plane using the Laplace transform technique are established. Expressions for velocity and temperature are obtained and displayed graphically for different values of Prandtl number Pr, thermal Grashof number Gr, viscoelastic parameter α, phase angle ωτ and time τ. Numerical values of skin friction τ 0 and Nusselt number Nu are shown in tables. Some well-known solutions in literature are reduced as the limiting cases of the present solutions.
Aldazines (Bis-Schiff bases) 1-24 were synthesized using aromatic aldehydes (heterocyclic and benzaldehydes) and hydrazine hydrate under reflux using conventional heating and/or via ultrasound irradiation using BiCl3 as catalyst. Ultrasonication conditions with cat. BiCl3 proved to be an effective, environmentally friendly synthetic procedure. This methodology is robust in the presence of electron donating and electron withdrawing groups affording desired products with high yields (>95%) in just a couple of minutes vs. hours using conventional heating.
A recombinant Trichoderma reesei cellulase was used for the ultrasound-mediated hydrolysis of soluble carboxymethyl cellulose (CMC) and insoluble cellulose of various particle sizes. The hydrolysis was carried out at low intensity sonication (2.4-11.8 W cm(-2) sonication power at the tip of the sonotrode) using 10, 20, and 40% duty cycles. [A duty cycle of 10%, for example, was obtained by sonicating for 1 s followed by a rest period (no sonication) of 9 s.] The reaction pH and temperature were always 4.8 and 50°C, respectively. In all cases, sonication enhanced the rate of hydrolysis relative to nonsonicated controls. The hydrolysis of CMC was characterized by Michaelis-Menten kinetics. The Michaelis-Menten parameter of the maximum reaction rate Vmax was enhanced by sonication relative to controls, but the value of the saturation constant Km was reduced. The optimal sonication conditions were found to be a 10% duty cycle and a power intensity of 11.8 W cm(-2) . Under these conditions, the maximum rate of hydrolysis of soluble CMC was nearly double relative to control. In the hydrolysis of cellulose, an increasing particle size reduced the rate of hydrolysis. At any fixed particle size, sonication at a 10% duty cycle and 11.8 W cm(-2) power intensity improved the rate of hydrolysis relative to control. Under the above mentioned optimal sonication conditions, the enzyme lost about 20% of its initial activity in 20 min. Sonication was useful in accelerating the enzyme catalyzed saccharification of cellulose.
This study was to investigate the mineralization of wastewater containing methyl orange (MO) in integrated anaerobic-aerobic biofilm reactor with coconut fiber as bio-material. Different aeration periods (3h in phase 1 and 2; 3, 6 and 15 h in phase 3; 24 h in phase 4 and 5) in aerobic chamber were studied with different MO concentration 50, 100, 200, 200 and 300 mg/L as influent from phase 1-5. The color removals estimated from the standard curve of dye versus optical density at its maximum absorption wavelength were 97%, 96%, 97%, 97%, and 96% and COD removals were 75%, 72%, 63%, 81%, and 73% in phase 1-5, respectively. The MO decolorization and COD degradation followed first-order kinetic model and second-order kinetic model, respectively. GC-MS analysis indicated the symmetrical cleavage of azo bond and the reduction in aromatic peak ensured the partial mineralization of MO.
High PHA production and storage using palm oil mill effluent (POME) was investigated using a laboratory batch Bio-PORec® system under aerobic-feeding conditions. Results showed that maximum PHA was obtained at a specific rate (q(p)) of 0.343 C-mol/C-molh when air was supplied at 20 ml/min. The PHA yield was found to be 0.80 C-mol/C-mol acetic acid (HAc) at microaerophilic condition and the mass balance calculation showed that PHA production increased up to 15.68±2.15 C-mmol/cycle. The experiments showed that short feeding rate, limited requirements for electron acceptors (e.g. O(2), NO(3)) and nutrients (N and P) showed lower tendency of glycogen accumulation and contributed more to PHA productivity.
Methyl esters were synthesized from crude karanj oil (CKO) by single step esterification with methanol using sulfuric acid (H(2)SO(4)) and phosphoric acid (H(3)PO(4)) as catalysts in a homogeneous batch process. H(3)PO(4) was less active than H(2)SO(4) during the process as it presented very low ester yields (<20%) for the various molar ratios of fatty acid to alcohol studied. With H(2)SO(4) as catalyst, the yield was as high as 89.8% at 65°C after 5h. The fatty acids profile of the oil (palmitic acid: ≈ 12%; stearic acid: ≈ 8%; oleic acid: ≈ 52% and linolenic acid of 17%) and the different reactivities of the acids were responsible for the observed differences in conversion to methyl esters. The findings attained with this study might contribute to the economic utilization of a non-edible feedstock.
The objectives of this study are to obtain the time courses of the amount of chlorophenol adsorbed onto granular activated carbon (GAC) in the simultaneous adsorption and biodegradation processes involving 4-chlorophenol (4-CP) and 2,4-dichlorophenol (2,4-DCP), respectively, and to quantify the bioregeneration efficiency of GAC loaded with 4-CP and 2,4-DCP by direct measurement of the amount of chlorophenol adsorbed onto GAC. Under abiotic and biotic conditions, the time courses of the amount of chlorophenol adsorbed onto GAC at various GAC dosages for the initial 4-CP and 2,4-DCP concentrations below and above the biomass acclimated concentrations of 300 and 150 mg/L, respectively, were determined. The results show that the highest bioregeneration efficiency was achieved provided that the initial adsorbate concentration was lower than the acclimated concentration. When the initial adsorbate concentration was higher than the acclimated concentration, the highest bioregeneration efficiency was achieved if excess adsorbent was used.
The objective of the present investigation was to study the effect of β-cyclodextrin (β-CD) on the in vitro dissolution of aceclofenac (AF) from molecular inclusion complexes. Aceclofenac molecular inclusion complexes in 1:1 and 1:2 M ratio were prepared using a kneading method. The in vitro dissolution of pure drug, physical mixtures, and cyclodextrin inclusion complexes was carried out. Molecular inclusion complexes of AF with β-CD showed a considerable increase in the dissolution rate in comparison with the physical mixture and pure drug in 0.1 N HCl, pH 1.2, and phosphate buffer, pH 7.4. Inclusion complexes with a 1:2 M ratio showed the maximum dissolution rate in comparison to other ratios. Fourier transform infrared spectroscopy and differential scanning calorimetry studies indicated no interaction between AF and β-CD in complexes in solid state. Molecular modeling results indicated the relative energetic stability of the β-CD dimer-AF complex as compared to β-CD monomer-AF. Dissolution enhancement was attributed to the formation of water soluble inclusion complexes with β-CD. The in vitro release from all the formulations was best described by first-order kinetics (R(2) = 0.9826 and 0.9938 in 0.1 N HCl and phosphate buffer, respectively) followed by the Higuchi release model (R(2) = 0.9542 and 0.9686 in 0.1 N HCl and phosphate buffer, respectively). In conclusion, the dissolution of AF can be enhanced by the use of a hydrophilic carrier like β-CD.
In this study, the kinetic parameters of rice husk ash (RHA)/CaO/CeO(2) sorbent for SO(2) and NO sorptions were investigated in a laboratory-scale stainless steel fixed-bed reactor. Data experiments were obtained from our previous results and additional independent experiments were carried out at different conditions. The initial sorption rate constant (k(0)) and deactivation rate constant (k(d)) for SO(2)/NO sorptions were obtained from the nonlinear regression analysis of the experimental breakthrough data using deactivation kinetic model. Both the initial sorption rate constants and deactivation rate constants increased with increasing temperature, except at operating temperature of 170 °C. The activation energy and frequency factor for the SO(2) sorption were found to be 18.0 kJ/mol and 7.37 × 10(5)cm(3)/(g min), respectively. Whereas the activation energy and frequency factor for the NO sorption, were estimated to be 5.64 kJ/mol and 2.19 × 10(4)cm(3)/(g min), respectively. The deactivation kinetic model was found to give a very good agreement with the experimental data of the SO(2)/NO sorptions.
The capability of carbon nanotubes (CNTs) to adsorb lead (Pb) in aqueous solution was investigated. Batch mode adsorption experiment was conducted to determine the effects of pH, agitation speed, CNTs dosage and contact time. The removal of Pb(II) reached maximum value 85% or 83% at pH 5 or 40 mg/L of CNTs, respectively. Higher correlation coefficients from Langmuir isotherm model indicates the strong adsorptions of Pb(II) on the surface of CNTs (adsorption capacity Xm = 102.04 mg/g). The results indicates that the highest percentage removal of Pb (96.03%) can be achieved at pH 5, 40 mg/L of CNTs, contact time 80 min, and agitation speed 50 r/min.
A mathematical model describing chemical kinetics of transesterification of palm-based methyl esters with trimethylolpropane has been developed. The model was developed by utilizing nonlinear regression method, which is an efficient and powerful way to determine rate constants for both forward and reverse reactions. A comparison with previous study which excludes the reverse reactions was made. The model was based on the reverse mechanism of transesterification reactions and describes concentration changes of trimethylolpropane, monoesters and diesters production. The developed model was validated against data from the literature. The reaction rate constants were determined using MATLAB version 7.2 and the ratios of rate constants obtained were well in agreement with those reported in the literature. A good correlation between model simulations and experimental data was observed. It was proven that both methods were able to predict the rate constants with plausible accuracy.