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Nanocellulose for biosorption of chlorpyrifos from water: chemometric optimization, kinetics and equilibrium
No full textThe study explores the biosorption potential
of nanocellulose (NC) to remove an insecticide,
chlorpyrifos (CP), from aqueous solutions using the
batch method. Biosorption kinetics were very fast and
reached equilibrium in 60 min, and the experimental
kinetic data had fit well with the pseudo-second-order
model. Film diffusion was the rate-limiting step for the
biosorption of CP onto crystalline nanocellulose
(CNC). The equilibrium sorption was well described
by the Sips and Langmuir isothermmodels. The values
of maximum sorption capacities (7.237–5.017 mg/g
for the Sips and 12.325–7.247 mg/g for the Langmuir
model) decreased with an increase in temperature
from 288 to 308 K, signifying biosorption of CP is an
exothermic process. Based on the central composite
design (CCD), two-factor interaction (2FI) and quadratic
models, the correlation between the effects of
variable parameters on the CP biosorption onto NC
was evaluated. The chemometric analyses suggested
that 1.5 g/l NC required 20 min to biosorb 5 mg/l CP
to yield an efficiency of 99.3%. Overall, the results
demonstrated that NCs can be a promising biosorbent
for the removal of pesticides from aqueous streams
Combined Electro-Fenton and Biological Processes for the Treatment of Industrial Textile Effluent: Mineralization and Toxicity Analysis
No full textThe longer time required for complete mineralization in the electro-Fenton (EF) process can be rectified by combining the EF
process with a biological method. This paper analyzes textile wastewater treatment by integrating EF and biological processes. The removal
of color, chemical oxygen demand (COD), and total organic carbon (TOC) by the EF process was 63, 48, and 29% respectively. Further
treatment of this wastewater by a biological process resulted in removal of 85% of color, 86% of COD, and 56% of TOC. In addition, better
mineralization of dyes requires integration of aerobic and microaerophilic conditions. The phytotoxicity and microbial toxicity analysis of
the treated wastewater shows that there is a significant reduction of toxicity compared with the raw wastewater. Therefore it is recommended
that the combined EF and biological degradation processes be applied in the treatment of textile wastewater for removing color, COD, and
TOC effectively
Solvent-free, improved synthesis of pure bixbyite phase of iron and manganese mixed oxides as low-cost, potential oxygen carrier for chemical looping with oxygen uncoupling
No full textChemical looping with oxygen uncoupling (CLOU) is the tendency of releasing gaseous oxygen of an
oxygen carrier upon heating, which is the key property for the efficient and cleaner combustion of solid fuels
for their wide exploitation for thermal power applications. The solvent-free, improved synthesis method was
developed for the synthesis of pure bixbyite, FeMnO3 (Ia3̅, a = b = c = 0.94 nm) as a low-cost, oxygen carrier
by exposing of the abundantly available precursors (Fe3O4 and MnO) under inert- or reduction- atmosphere
followed by air at 900 °C. The bixbyite FeMnO3 showed the enhanced, stable multi-cycle CLOU performance
than that of the physical mixture and it is converted into FeMn2O4 after the complete exhaustion of reactive
oxygen under CLOU conditions. FeMnO3 showed the uniform elemental distribution of Fe, Mn and O, which
facilitate the regeneration in air upon heating for multi-cycle performance. 3.2 wt.% of reactive oxygen can
be obtained compared to the mass of FeMnO3 which is almost equal to the theoretical value under CLOU
conditions. The lattice of FeMnO3 is altered linearly above 100 °C with the increase of temperature, however;
without the decomposition of the bixbyite phase and it was reinstated virtually upon cooling in air
Plasmonic nanostructured Zn/ZnO composite enhances carbonic anhydrase driven photocatalytic hydrogen generation
No full textHydrogen is produced from water by electrolysis or photolysis. Although, photocatalysis demands significantly less energy, it has several problem issues; slower production rate, consumption of sacrificial donors or need for expensive noble metals. Here, we report substantial increase in the rate of hydrogen evolution without the use of sacrificial donors or noble metals. We demonstrate appreciable hydrogen generation by coupling biomimetic carbonation with common metal driven plasmonic photocatalysis. Our process has three parts. First, zinc leads to the formation of Zn/ZnO composite, which acts as the proximate photocatalyst. Second, specific illumination operates on the composite via Surface Plasmon Resonance (SPR), a phenomenon in which photons activated nanoparticles exhibit local heating, concentration and redistribution of the incident light and release of electrons. Third, carbonic anhydrase catalyzes the hydrolysis of water by CO2 to provide both protons and bicarbonate ions critical to the process. In sum, protons derived from water combine with electrons derived photocatalytically from Zn/ZnO to yield hydrogen. Only photons and water are consumed and only hydrogen is produced. The SPR sensitive Zn/ZnO composite generates hydrogen evolution at a rate of 1238 μmol h−1, an unprecedented enhancement (16.7-fold) over zinc micro particles − Zn(M) alone. The system is unique and low cost and avoids the use of noble metal and organic donors
Titania Gold composite: Effect of Illumination on size of gold nanoparticles with consequent implication on photocatalytic water splitting�
No full textThis work deals with the study of photodeposition (PD) of gold nanoparticles (AuNPs) on TiO2 by using different illumination sources, Medium pressure Mercury lamp (ML), Solar Simulator equipped with AM 1.5 (SL) & Tungsten lamp (WL). Different particle size of AuNPs on TiO2 were obtained by photodeposition method under different illumination sources, which clearly proves the influence of light source on the synthesis of Au-TiO2. The plasmonic activity of Au-TiO2 photocatalyst for water splitting reaction was observed to be strongly influenced by the particle size of Au as well as illumination source. Amongst the three different illumination sources used, smallest particle size for AuNP-TiO2 were observed under ML followed by SL and WL, as revealed by TEM analysis. Different illumination sources were also investigated to evaluate the activity of Au-TiO2 samples thus prepared under different illumination conditions. The order of hydrogen evolution rate (HER) observed for Au-TiO2 with different source of illuminations is ML > SL > WL. The highest HER of 1709 µmol/h was observed for Au-TiO2, which was synthesized and evaluated under ML irradiation. This may be explained on the basis of reduced catalytic activity and photothermal effect of Au nanoparticles with increasing particle size
Application of cell-based assays for toxicity characterization of complex wastewater matrices: Possible applications in wastewater recycle and reuse
No full textExposure to pre-concentrated inlet or outlet STP wastewater extracts at different concentrations (0.001% to 1%)
induced dose-dependent toxicity in MCF-7 cells, whereas drinking water extracts did not induce cytotoxicity in
cells treated. GC-MS analysis revealed the occurrence of xenobiotic compounds (Benzene, Phthalate, etc.) in
inlet/outlet wastewater extracts. Cells exposed to inlet/outlet extract showed elevated levels of reactive oxygen species (ROS: inlet: 186.58%, p<0.05, outlet, 147.8%, p<0.01) and loss of mitochondrial membrane potential
(Δψm: inlet, 74.91%, p<0.01; outlet, 86.70%, p<0.05) compared to the control. These concentrations
induced DNA damage (Tail length: inlet: 34.4%, p<0.05, outlet, 26.7%, p<0.05) in treated cells compared to
the control (Tail length: 7.5%). Cell cycle analysis displayed drastic reduction in the G1 phase in treated cells
(inlet, G1:45.0%; outlet, G1:58.3%) compared to the control (G1:67.3%). Treated cells showed 45.18% and
28.0% apoptosis compared to the control (1.2%). Drinking water extracts did not show any significant
alterations with respect to ROS, Δψm, DNA damage, cell cycle and apoptosis compared to the control. Genes
involved in cell cycle and apoptosis were found to be differentially expressed in cells exposed to inlet/outlet
extracts. Herein, we propose cell-based toxicity assays to evaluate the efficacies of wastewater treatment and
recycling processes
Carbamazepine and oxcarbazepine removal in pharmaceutical wastewater treatment plant using a mass balance approach: A case study
No full textThe manufacturing of the antiepileptics, carbamazepine (CBZ) and oxcarbazepine (oxCBZ), results in generation
of wastewater containing these micropollutants which exhibit toxicity even at trace levels. Therefore, we focused on monitoring their fate and removal in various units of a full-scale wastewater treatment plant (WWTP) using mass balance approach. An apparent CBZ removal of 50±3% was observed by conventional activated sludge process in the biological treatment unit, whereas oxCBZ still persisted after the biological treatment and showed negative mass balance. However, reverse osmosis resulted in 91% oxCBZ removal, whereas CBZ still continued to persist as a result of lower solubility of CBZ as compared to oxCBZ. Only 3% CBZ exhibited sorption onto the suspended solids and sludge, which was negligible for oxCBZ, thus demonstrating their tendency to remain in aqueous phase. Additionally, we attempted to understand the fundamental mechanism behind the removal of these pharmaceuticals and it was apparently the collective effect of sorption, mineralization, biotransformation, biodegradation, phototransformation/photodegradation, etc. Thus, the integrative data presented in the present study on productivity of these pharmaceuticals, their mass loading in influent and effluents allied with their removal efficiency will be significantly constructive in
benchmarking the operational effectiveness through operational optimization and design improvement of the current conventional treatment plant
On H2 supply through liquid organic hydrides e Effect of functional groups
No full textLiquid organic hydride (LOH) based H2 supply systems possess an excellent potential to
overcome the obstacles of upcoming ‘hydrogen economy’. However, their efficiency mainly
relies on the choice of organic hydride and the dehydrogenation catalyst. In the present
study, we focused on the former to strengthen the understanding of H2 supply through
LOH dehydrogenation. We investigated the role of various functionalities viz., methyl
group, N heteroatom, cyclic ring and their combinations in LOH dehydrogenation. Several
simple representative LOH's such as methylcyclohexane, piperidine, 4-methylpiperidine
and decalin were considered and their dehydrogenation was studied over a 5 wt% Pt/
ACC catalyst in a spray pulse reactor at 350 �C. The H2 evolution rates were found to follow
the trend: cyclohexane < methylcyclohexane < piperidine < 4-methylpiperidine < decalin.
The inductive effects caused by these functional groups and their impact on H2 evolution
were comprehensively described. Finally, the results were compared with the benchmark
reaction, cyclohexane dehydrogenation to benzene
CFD Analysis of Flow Regimes in Airlift Reactor Using Eulerian-Lagrangian Approach
No full textThe hydrodynamic aspects of the concentric tube airlift reactor have been studied using two-phase CFD simulations with a Eulerian-Lagrangian
approach. The three-dimensional CFD simulations are carried out with the experimental geometry of airlift reactor (H/D ¼ 12) reported in the
published literature. The standard k-e turbulence model is used with additional consideration of production and dissipation of buoyancy-induced
turbulence. Two different bubble size distributions (BSDs) and their Sauter mean diameters have been considered to represent the gas distribution at
sparger in the reactor. This study shows that the BSD1 (1–5–10 mm) containing a high fraction of small bubbles (� 5 mm) represents the
hydrodynamics of flows appropriately as compared to the BSD2 (5–10–15 mm) containing a high fraction of large bubbles (� 10 mm) or the single
size bubble diameters (5.25 mm and 10 mm). Further, three regimes of operation such as no gas bubbles in the downcomer (regime I), stationary
gas bubbles in the downcomer (regime II), and gas bubble recirculation from the downcomer section to the riser section (regime III), are verified
using CFD simulations with Lagrangian particle tracking. Satisfactory agreement (within 15 %deviation) with the experimental data was observed
for parameters such as the gas holdups in the riser and downcomer and the liquid circulation velocity in the flow regimes I and II for BSD1