Experimental investigations were carried out to adsorb toxic brilliant green dye from aqueous medium using kaolin as an adsorbent. Characterization of kaolin is done by measuring: (i) particle size ...distribution using particle size analyzer, (ii) BET surface area using BET surface analyzer, and (iii) structural analysis using X-ray diffractometer. The effects of initial dye concentration, contact time, kaolin dose, stirring speed, pH and temperature were studied for the adsorption of brilliant green in batch mode. Adsorption experiments indicate that the extent of adsorption is strongly dependent on pH of solution. Free energy of adsorption (Δ
G
0), enthalpy (Δ
H
0) and entropy (Δ
S
0) changes are calculated to know the nature of adsorption. The calculated values of Δ
G
0 at 299
K and 323
K indicate that the adsorption process is spontaneous. The estimated values of Δ
H
0 and Δ
S
0 both show the negative sign, which indicate that the adsorption process is exothermic and the dye molecules are organized on the kaolin surface in less randomly fashion than in solution. The adsorption kinetic has been described by first-order, pseudo-second-order and intra-particle-diffusion models. It was observed that the rate of dye adsorption follows pseudo-second-order model for the dye concentration range studied in the present case. Standard adsorption isotherms were used to fit the experimental equilibrium data. It was found that the adsorption of brilliant green on kaolin follows the Langmuir adsorption isotherm.
Experimental investigations were carried out using commercially available kaolin to adsorb two different toxic cationic dyes namely crystal violet and brilliant green from aqueous medium. Kaolin was ...characterized by performing particle size distribution, BET surface area measurement and XRD analysis. The effects of initial dye concentration, contact time, adsorbent dose, stirring speed, pH, salt concentration and temperature were studied in batch mode. The extent of adsorption was strongly dependent on pH of solution. Free energy of adsorption (Δ
G
0), enthalpy (Δ
H
0) and entropy (Δ
S
0) changes were calculated. Adsorption kinetic was verified by pseudo-first-order, pseudo-second-order and intra-particle-diffusion models. The rate of adsorption of both crystal violet and brilliant green followed the pseudo-second-order model for the dye concentrations studied in the present case. The dye adsorption process was found to be external mass transfer controlled at earlier stage and intra-particle diffusion controlled at later stage. Calculated external mass transfer coefficient showed that crystal violet dye adsorbed faster than brilliant green on kaolin. Adsorption of crystal violet and brilliant green on kaolin followed the Langmuir adsorption isotherm.
Contemporary research in ceramic composites for membrane applications targets the fabrication of stable low cost micro-filtration range membranes. This work reports the fabrication of stable low cost ...mesoporous membranes deploying subsequent formulations based on kaolin and other suitable low cost materials such as quartz, sodium carbonate, calcium carbonate, boric acid and sodium metasilicate. Incidentally, the processing temperature in this work is about 850–1000 °C instead of 1100 °C which is the usual sintering temperature for inorganic membrane fabrication. The membranes casted as circular disks (52.5 mm diameter and 4.5 mm thickness) were subjected for characterization studies using TGA, XRD, SEM analysis, to evaluate the effect of maximum sintering temperature on membrane structure, porosity and mechanical integrity. Pore size distribution, porosity, average pore size of the membrane along with permeation experiments with both water and air is carried out to study the membrane performance. The average pore size of the membrane is observed to increase from 550 nm to 810 nm when sintering temperature increases from 850 °C to 1000 °C. However, with the increase in temperature from 850 °C to 1000 °C, the membrane porosity is reduced (from 42% to 33%) and flexural strength is increased (from 3 to 8 MPa). The membrane corrosion resistance is found to be unaltered with processing temperature. Based on raw-material prices, the membrane cost is estimated to be $130/m
2. Henceforth, these low cost membranes with good membrane properties are suggested for cheaper application in chemical and biochemical processes using micro-filtration and ultra-filtration techniques.
This work addresses the performance and modeling of the separation of oil-in-water (o/w) emulsions using low cost ceramic membrane that was prepared from inorganic precursors such as kaolin, quartz, ...feldspar, sodium carbonate, boric acid and sodium metasilicate. Synthetic o/w emulsions constituting 125 and 250
mg/L oil concentrations were subjected to microfiltration (MF) using this membrane in batch mode of operation with varying trans-membrane pressure differentials (Δ
P) ranging from 68.95 to 275.8
kPa. The membrane exhibited 98.8% oil rejection efficiency and 5.36
×
10
−6
m
3/m
2
s permeate flux after 60
min of experimental run at 68.95
kPa trans-membrane pressure and 250
mg/L initial oil concentration. These experimental investigations confirmed the applicability of the prepared membrane in the treatment of o/w emulsions to yield permeate streams that can meet stricter environmental legislations (<10
mg/L). Subsequently, the experimental flux data has been subjected to modeling study using both conventional pore blocking models as well as back propagation-based multi-layer feed forward artificial neural network (ANN) model. Amongst several pore blocking models, the cake filtration model has been evaluated to be the best to represent the fouling phenomena. ANN has been found to perform better than the cake filtration model for the permeate flux prediction with marginally lower error values.
Summary
A large recurrent scalp tumour was excised. The exposed skull bones on the left side were covered successfully by using a large trapezius myocutaneous flap with a good result.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
•Early-stage, large-scale SARS-CoV-2 serosurvey combining PCR and sVNT in Africa•SARS-CoV-2 prevalence and immunity is grossly underestimated by official surveillance•Asymptomatic and subclinical ...infection and transmission are high•targeted risk group approach preferable over undirected lockdown measures•Conduction of sVNT is feasible even with limited laboratory infrastructure
COVID-19 transmission and disease dynamics in sub-Saharan Africa are not well understood. Our study aims to provide insight into COVID-19 epidemiology in Malawi by estimating SARS-CoV-2 prevalence and immunity after SARS-CoV-2 infection in a hospital-based setting.
We conducted a hospital-based, convenience sampling, cross-sectional survey for SARS-CoV-2 in Lilongwe, Malawi. Participants answered a questionnaire and were tested for SARS-CoV-2 by enzyme-linked immunosorbent assay and real-time reverse-transcription polymerase chain reaction (RT-PCR). A surrogate virus neutralization test (sVNT) was performed in seropositive samples to estimate immunity. Poisson regression was used to assess SARS-CoV-2 point prevalence association with demographic and behavioral variables.
The study included 930 participants. We found a combined point prevalence of 10.1%. Separately analyzed, RT-PCR positivity was 2.0%, and seropositivity was 9.3%. Of tested seropositive samples, 90.1% were sVNT positive. We found a high rate (45.7%) of asymptomatic SARS-CoV-2 infection. SARS-CoV-2 point prevalence was significantly associated with being a healthcare worker.
Our study suggests that official data underestimate COVID-19 transmission. Using sVNTs to estimate immunity in Malawi is feasible and revealed considerable post-infection immunity in our cohort. Subclinical infection and transmission are probably a game-changer in surveillance, mitigation and vaccination strategies.
The scenario of developed and developing countries nowadays is disturbed due to modern living style which affects environment, wildlife and natural habitat. Environmental quality has become or is a ...subject of major concern as it is responsible for health hazard of mankind and animals. Measurements and prediction of hazardous parameters in different fields of environment is a recent research topic for safety and betterment of people as well as nature. Pollution in nature is an after-effect of civilization. To combat the damage already happened, some processes should be evolved for measurement and prediction of pollution in various fields. Researchers of all over the world are active to find out ways of predicting such hazard. In this paper, application of neural network and deep learning algorithms is chosen for air pollution and water pollution cases. The purpose of this review is to reveal how family of neural network algorithms has applied on these two pollution parameters. In this paper, importance is given on algorithm, and datasets used for air and water pollution as well as the predicted parameters have also been noted for ease of future development. One major concern of this paper is Indian context of air and water pollution research, and the research potential presents in this area using Indian dataset. Another aspect for including both air and water pollutions in one review paper is to generate an idea of artificial neural network and deep learning techniques which can be cross applicable for future purpose.
This work addresses the applicability of different membrane pore blocking models for the prediction of flux decline mechanisms during dead end microfiltration (MF) of stable oil-in-water (o/w) ...emulsions using relatively low-cost ceramic membranes. Circular disk type membranes (52.5 mm diameter and 4.5 mm thickness) were prepared by the paste method using locally available low-cost inorganic precursors such as kaolin, quartz, calcium carbonate, sodium carbonate, boric acid, and sodium metasilicate. Characterization of the prepared membrane was done by SEM analysis, porosity determination, and pure water permeation through the membrane. Hydraulic pore diameter, hydraulic permeability, and hydraulic resistance of the membrane was evaluated as 0.7 µm, 1.94 × 10
−6
m
3
/m
2
·s·kPa and 5.78 × 10
11
m
2
/m
3
, respectively. The prepared membrane was used for the treatment of synthetic stable o/w emulsions of 40 and 50 mg/L crude oil concentration in batch mode with varying trans-membrane pressure differentials ranging from 41.37 to 165.47 kPa. The membrane exhibited 96.97% oil rejection efficiency and 21.07 × 10
−6
m
3
/m
2
·s permeate flux after 30 min of experimental run at 165.47 kPa trans-membrane pressure for 50 mg/L oil concentration. Different pore blocking, models such as complete pore blocking, standard pore blocking, intermediate pore blocking and cake filtration were used to gain insights into the nature of membrane fouling during permeation. The observed trends for flux decline data convey that the decrease in permeate flux was initially due to intermediate pore blocking (during 1 to 10 minutes of experimental run) followed with cake filtration (during 10 to 30 minutes of experimental run). Based on retail prices of the inorganic precursors, the membrane cost was estimated to be 130 $/m
2
. Finally, preliminary process economic studies for a single stage membrane plant were performed for the application of the prepared membrane in industrial scale treatment of o/w emulsions. A process economics study inferred that the annualized cost of the membrane plant would be 0.098 $/m
3
feed for treating 100 m
3
/day feed with oil concentration of 50 mg/L.
Saint Venant equations are numerically solved to simulate the formation of hydraulic jump in a rectangular channel having a small bed slope. The MacCormack's scheme is used for the solution by ...applying specified initial and boundary conditions until a steady state flow is reached. The location of the hydraulic jump is determined as a part of these computations. The artificial viscosity technique should be used in the computations to dampen the superior oscillations near the steep gradient of the simulated hydraulic jump. Twenty laboratory experiments were carried out for verification of the numerical model. The upstream Froude number for these experiments ranged from 2.17 to 7.0 in three different bed slopes 0, 0.02174, 0.0475. The simulated hydraulic jump profiles using the MacCormack's scheme shows a good agreement with the experimental data. An empirical equation was developed to determine the location of hydraulic jump using regression analysis based on simulated data. Software based on Computational Fluid Dynamics (CFD) was also used to simulate two of these experiments. The results obtained from CFD analysis matched fairly with the experimental results.
In this work, experimental investigations were carried out for the identification of optimal membrane morphological parameters (pore size distribution, average pore size and porosity) during ...microfiltration (MF) of mosambi juice using low cost ceramic membranes. Four different low cost ceramic membranes with different pore diameters (
d
m) and porosities (
ɛ) were subjected to MF studies to evaluate the effect of
d
m and
ɛ on permeation characteristics (permeate flux and juice quality) of centrifuged mosambi juice (CJ) and enzyme treated centrifuged mosambi juice (ETCJ). Subsequently, a convenient factor namely effective permeable area factor (
ɛ
m
d
m
2) was evaluated to provide greater insights in the fouling phenomena. Various physio-chemical properties such as colour, clarity, pH, citric acid content, density, total soluble solid (TSS) and alcohol insoluble solids (AIS) were measured for both feed and permeate juice samples to evaluate the effect of
ɛ
m
d
m
2 on juice quality. Typical permeate fluxes were observed to vary from 5.78
×
10
−6 to 13.45
×
10
−6
m
3/m
2
s for CJ and 14.07
×
10
−6 to 60.64
×
10
−6
m
3/m
2
s for ETCJ at 82.7
kPa (Δ
P) for different membranes whose
ɛ
m
d
m
2 varied from 0.249 to 0.783
μm
2. Among different membrane pore blocking models, flux decline by cake filtration was found to be the best fitted model. The cake filtration model constant (
k
c) was found to vary with Δ
P and
ɛ
m
d
m
2 and was empirically correlated. Phenomenological models were proposed to illustrate the dependency of total hydraulic resistance of membrane on
ɛ
m
d
m
2, Δ
P and time (
t). Based on experimental as well as theoretical investigations, membranes with
ɛ
m
d
m
2 up to 0.443
μm
2 for CJ and 0.294
μm
2 for ETCJ and a Δ
P of 82.7
kPa were recommended for MF of mosambi juice.
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