First-order Rate Model Research Articles

Synthesis and characterization of Gellan gum-based hydrogels for the delivery of anticancer drug etoposide

Present research work reports the synthesis of Gellan gum (Gg) and methacrylic acid (MA) based grafted hydrogels (Gg-cl-poly(MA)) crosslinked using N, N′– methylene-bis-acrylamide (MBA) and the evaluation of their efficiency to be used as a sustained drug delivery carrier for anticancer drug i.e., etoposide. Various characterization techniques like Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) confirmed the grafting of Gg with MA and the formation of crosslinked Gg-cl-poly(MA) hydrogel polymer. The synthesized hydrogel showed pH-dependent swelling properties and exhibited a maximum swelling capacity of 867 % under optimized environmental conditions. The Gg-cl-poly(MA) was biocompatible and non-cytotoxic, which was confirmed by the hemolytic and cytotoxic tests. The release dynamics of etoposide from the Gg-cl-poly(MA) polymer matrix was checked under specific physiological conditions. Drug release was found to be significantly higher in the acidic medium, followed by the neutral and alkaline medium. This clearly indicated that etoposide drug release through synthesized hydrogel was stomach-specific and it is effective for the treatment of stomach cancer. The release mechanism of the etoposide drug was a Fickian-type diffusion mechanism in the acidic medium and a non-Fickian-type diffusion mechanism in the neutral and alkaline medium. The release profile of the etoposide was best fitted to the first-order rate model. The results showed that the synthesized hydrogel (i.e., Gg-cl-poly(MA)) was biocompatible, non-toxic, and could be used for the treatment of stomach cancer.

Evaluating and modeling the efficacy of Stipagrostis plumosa for the phytoremediation of petroleum compounds in crude oil-contaminated soil

ABSTRACT This study focused on using Stipagrostis plumosa for phytoremediation to eliminate total petroleum hydrocarbons (TPHs) and heavy metals (HMs) like cadmium (Cd), chromium (Cr), lead (Pb), and nickel (Ni) from oil-contaminated soil. Conducted over six months at a field-scale without artificial pollutants, soil samples were analyzed using gas chromatography‒mass spectrometry (GC‒MS) for TPHs and inductively coupled plasma-optical emission spectroscopy (ICP‒OES) for HMs. Results after six months revealed that plots with plants had significantly higher average removal percentages for TPHs (61.45%), Cd (39.4%), Cr (46.1%), Pb (41.5%), and Ni (44.2%) compared to the control group (p <0.05). Increased microbial respiration and bacteria populations in planted plots indicated enhanced soil microbial growth. Kinetic rate models aligned well with the first-order kinetic rate model for all pollutants (R2 >0.9). Overall, the study demonstrates that S. plumosa can effectively reduce TPHs and HMs in oil-contaminated soil, making it a promising option for pollutant absorption.

Phytoremediation of pollutants in oil-contaminated soils by Alhagi camelorum: evaluation and modeling

Phytoremediation is a cost-effective and environmentally friendly method, offering a suitable alternative to chemical and physical approaches for the removal of pollutants from soil. This research explored the phytoremediation potential of Alhagi camelorum, a plant species, for total petroleum hydrocarbons (TPHs) and heavy metals (HMs), specifically lead (Pb), chromium (Cr), nickel (Ni), and cadmium (Cd), in oil-contaminated soil. A field-scale study spanning six months was conducted, involving the cultivation of A. camelorum seeds in a nursery and subsequent transplantation of seedlings onto prepared soil plots. Control plots, devoid of any plants, were also incorporated for comparison. Soil samples were analyzed throughout the study period using inductively coupled plasma-optical emission spectroscopy (ICP‒OES) for HMs and gas chromatography‒mass spectrometry (GC‒MS) for TPHs. The results showed that after six months, the average removal percentage was 53.6 ± 2.8% for TPHs and varying percentages observed for the HMs (Pb: 50 ± 2.1%, Cr: 47.6 ± 2.5%, Ni: 48.1 ± 1.6%, and Cd: 45.4 ± 3.5%). The upward trajectory in the population of heterotrophic bacteria and the level of microbial respiration, in contrast to the control plots, suggests that the presence of the plant plays a significant role in promoting soil microbial growth (P < 0.05). Moreover, kinetic rate models were examined to assess the rate of pollutant removal. The coefficient of determination consistently aligned with the first-order kinetic rate model for all the mentioned pollutants (R2 > 0.8). These results collectively suggest that phytoremediation employing A. camelorum can effectively reduce pollutants in oil-contaminated soils.

Sorption of cadmium, chromium, lead, and vanadium from artificial wetlands using Lemna aequinoctialis

The efficacy of the lesser duckweed, Lemna aequinoctialis (Welw.), to remediate varying concentrations of cadmium, chromium, lead, and vanadium from an organo-metallic contaminated media was tested in artificial surface wetland mesocosm experiment. A 100 g of fresh-weight duckweed was introduced into each of the mesocosm, except for the control setup and monitored for 120 days while the metals removal rate was quantified using an atomic absorption spectrometer. A time-dependent and partial sorption of metals was observed with the highest removal rate recorded for cadmium (71.96%), followed by lead (69.23%), vanadium (55.22%), and chromium (41.64%). The uptake and bioaccumulation of metals were reflected in the increased plant biomass (p < 0.05, F = 97.12) and relative growth rate (p < 0.05, F = 1214.35) in duckweed. A coefficient (r 2) of 0.951, 0.919, 0.970, and 0.967 was recorded for cadmium, chromium, lead, and vanadium respectively, indicating that the remediation of metals followed the first-order kinetic rate model. This study highlights the efficacy of the lesser duckweed to preferentially remediate metals in an organo-metallic complex medium for potential wastewater treatment in the petrochemical industry.

Sunlight photolysis of SARS-CoV-2 N1 gene target in the water environment: considerations for the environmental surveillance of wastewater-impacted surface waters.

Wastewater surveillance of SARS-CoV-2 has been used around the world to supplement clinical testing data for situational awareness of COVID-19 disease trends. Many regions of the world lack centralized wastewater collection and treatment infrastructure, which presents additional considerations for wastewater surveillance of SARS-CoV-2, including environmental decay of the RT-qPCR gene targets used for quantification of SARS-CoV-2 virions. Given the role of sunlight in the environmental decay of RNA, we evaluated sunlight photolysis kinetics of the N1 gene target in heat-inactivated SARS-CoV-2 with a solar simulator under laboratory conditions. Insignificant photolysis of the N1 target was observed in a photosensitizer-free matrix. Conversely, significant decay of the N1 target was observed in wastewater at a shallow depth (<1 cm). Given that sunlight irradiance is affected by several environmental factors, first-order decay rate models were used to evaluate the effect of water column depth, time of the year, and latitude on decay kinetics. Decay rate constants were found to decrease significantly with greater depth of the well-mixed water column, at high latitudes, and in the winter. Therefore, sunlight-mediated decay of the N1 gene target is likely to be minimal, and is unlikely to confound results from wastewater-based epidemiology programs utilizing wastewater-impacted surface waters.

Spatially Resolved Heterogeneous Electrocatalyst Degradation in Polymer Electrolyte Fuel Cells Subjected to Accelerated Aging Conditions

This work quantifies in-plane spatial heterogeneity (polymer electrolyte fuel cell cathode inlet vs outlet) in Pt particle size growth and distribution as a function of nitrogen (N2) flow rate during a square-wave accelerated stress test (AST). The average Pt particle sizes for membrane electrode assemblies (MEAs) subjected to N2 flow rates ranging from 4–16 sccm cm−2 are in the range 9–10.5 nm at the end-of-life (EOL) with similar electrochemically active surface area (ECSA) loss (∼65%). However, Pt particle size at EOL exhibits spatial heterogeneity: greater Pt particle size growth occurs near the flow field outlet than the inlet. The spatial heterogeneity for a fully-humidified N2 flow is believed to originate from non-uniform humidification (outlet is more humidified than the inlet) across the cell for a co-flow arrangement. A first-order rate model for ECSA loss predicts linear increase of the rate constant with N2 flow rate. The polarization losses of the aged MEAs over a wide range of operating conditions increase with N2 flow rate. From the results of this work, for holistically assessing durability of Pt catalysts in fuel cells at high humidity conditions, it is recommended to include purge gas flow rate as a stressor during an AST.

Ex-situ bioremediation of petroleum hydrocarbon contaminated soil using mixed stimulants: Response and dynamics of bacterial community and phytotoxicity

Pollution of agricultural soils by excessive petroleum hydrocarbons (PHs) has recently become a severe worldwide environmental issue. Various approaches have been recently employed to biodegrade PHs and detoxify soils. In the present study, an experimental mesocosm was developed in a bioslurry reactor. Six treatments were applied to degrade PHs-and detoxify contaminated soil by adding external stimulants such as nutrients, activated sludge, synthetic surfactant, and long-chain rhamnolipids. The comparative analysis revealed that the combination of activated sludge, nutrients, and biosurfactant showed a 79.4% reduction in TPHs after 10 days in the mesocosm experiment. The lowest reduction in total PHs (48.5 %) was attained in the nutrient-supplied mesocosms. The consortia’s kinetic analyses of PHs revealed the lowest half-life time (t1/2 = 4.1 days), the highest biodegradation rate constants (k = 0.17 day1), and the reaction rate data from each bioremediation method was fitted with a first-order reaction rate model. The 16S rRNA gene amplicon and sequencing revealed that Streptomyces, Nocardioides, Arthrobacter, Pseudomonas, and Bacillus were the main oxidative species as PHs degraders. The highest relative abundances were in Arthrobacter, Pseudomonas, and Bacillus. The phytotoxicity studies proved that there was a significant decrease in the toxicity of soil after the biotreatment. According to the findings of this study, adding external stimulants such as activated sludge, nutrients, and biosurfactants enhanced the degradation of PHs in the soil in bioslurry enhancement as a promising approach to pilot scale.

Influence of temperature and water quality on the persistence of human mitochondrial DNA, human Hf183 Bacteroidales, fecal coliforms and enterococci in surface water in human fecal source tracking context.

Mitochondrial DNA (mtDNA) is used as a genetic marker to track fecal contamination in surface water. Its potential to effectively discriminate between the nonpoint sources of fecal pollution (e.g. human, livestock) in water environments is relevant for water quality management. However, there is a lack of knowledge about the environmental persistence of mtDNA in relation to those of other microbial parameters, such as fecal indicator bacteria (FIB). In this study, mesocosms composed of water collected from four rivers and tap water were spiked with raw wastewater to mimic human fecal contamination. Mesocosms composed of raw wastewater were also studied. The mesocosms were incubated at 4 °C or at 22 °C for 189 days, from which the levels of human mtDNA (HumtDNA) and human Bacteroidales (Hf183) were measured by qPCR. The levels of FIB (fecal coliforms and enterococci) and heterotrophs were determined by culture methods along with the determination of physicochemical attributes. The decay rates of the genetic markers and FIB were determined with first-order decay rate models. The decay rates of HumtDNA (0.004-0.059 d-1), Hf183 (0.007-0.082 d-1), and the two FIBs (0.005-0.066 d-1) were similar at 4 °C, while the genetic markers both had higher decay rates (0.013-0.919 d-1) at 22 °C. Different HumtDNA decay rates were observed between the river mesocosms (0.043-0.919 d-1) and the wastewater and tap water mesocosms (0.004-0.095 d-1). Covariations of pH and conductivity among the HumtDNA, Hf183 and FIB decay rates were observed. HumtDNA and Hf183 had similar environmental persistence, whereas fecal coliforms and enterococci persisted longer at 22 °C. Finally, HumtDNA had the same trends of persistence in the four river mesocosms, suggesting a relative stability of this marker in different rivers. Our results suggest that HumtDNA could be more suitable for tracking the source of a recent fecal contamination in complement to FIB.

Denitrification kinetics during aquifer storage and recovery of drainage water from agricultural land

An aquifer storage transfer and recovery (ASTR) system was studied in which tile drainage water (TDW) was injected with relatively high NO3 (about 14 mg/L) concentrations originating from fertilizers. Here we present the evolution of denitrification kinetics at 6 different depths in the aquifer before, and during ASTR operation. First-order denitrification rate constants increased over time before and during the first days of ASTR operation, likely due to microbial adaptation of the native bacterial community and/or bioaugmentation of the aquifer by denitrifying bacteria present in injected TDW. Push-pull tests were performed in the native aquifer before ASTR operation. Obtained first-order denitrification rate constants were negligible (0.00–0.03 d−1) at the start, but increased to 0.17–0.83 d−1 after a lag-phase of about 6 days. During the first days of ASTR operation in autumn 2019, the arrival of injected TDW was studied at 2.5 m distance from the injection well. First-order denitrification rate constants increased again over time (maximum >1 d−1). Three storage periods without injection were monitored in winter 2019, fall 2020, and spring 2021 during ASTR operation. First-order rate constants ranged between 0.12 and 0.61 d−1. Denitrification coupled to pyrite oxidation occurred at all depths, but other oxidation processes were indicated as well. NO3 concentration trends resembled Monod kinetics but were fitted also to a first-order decay rate model to facilitate comparison. Rate constants during the storage periods were substantially lower than during injection, probably due to a reduction in the exchange rate between aquifer solid phases and injected water during the stagnant conditions. Denitrification rate constants deviated maximally a factor 5 over time and depth for all in-situ measurement approaches after the lag-phase. The combination of these in-situ approaches enabled to obtain more detailed insights in the evolution of denitrification kinetics during AS(T)R.

Facile and fast preparation of layered double hydroxide as a nanocarrier for ascorbic acid under ultrasonic irradiation.

Background and purpose:Layered double hydroxides (LDHs) as inorganic materials are being used in controlled release and drug delivery systems. These materials are more stable than conventional drug carriers. In this investigation, Mg/Al-ascorbic acid (ASA) LDH nanohybrid was synthesized by ultrasonic-assisted co-deposition techniques.Experimental approach:In this study, Mg/Al-LDH to adsorption of ASA anions from the alkaline solution was assembled by a facile coprecipitation technique. During this process, ultrasonic irradiation was used to increase the rate of ion exchange between LDH and ASA. The intercalated-layered structure was characterized by FT-IR spectroscopy, XRD, thermogravimetric analysis, field emission SEM, and TEM. ASA releasing from Mg/Al-ASA LDH nanohybrid was carried out in incubation sodium carbonate solution (0.5 M) at 35 °C using UV-Vis absorbance analysis at λ = 265 nmFindings/Results:The used techniques confirmed the structure of Mg/Al-LDH and indicated successful intercalation of ASA into the interlayer galleries of the LDH host. The obtained results also have shown that Mg/Al-ASA LDH nanohybrid was generated with an average diameter size of 25 nm and narrow size distribution. Analysis of the release profiles using several kinetic models suggested that the first-order rate model is the most appropriate for describing the release of ASA from Mg/Al-LDH which means the amount of drug released is proportional to the amount of remaining drug in the matrix. Thus, the amount of activity released tends to decrease in function of time.Conclusion and implications:The results showed that LDHs are good host materials to preserve the biomolecule and modify its release rate and bioavailability.

Toluene Bioremediation by Using Geotextile-Layered Permeable Reactive Barriers (PRBs)

Sources of contamination in a subsurface environment are petrol, diesel fuel, gasoline at oil refineries, underground storage tanks, transmission pipelines, and different industries. The permeable reactive barrier (PRB) is a promising technology to remediate groundwater in-situ. In this study, synthetic groundwater samples containing toluene are treated in three reactor columns by biological processes. PRB-1 consisted of sand and gravel as reactor media, microbial inoculum (bioaugmentation—BA), and nutrients (biostimulation—BS); PRB-2 consisted of sand and gravel as reactor media, microbial inoculum, nutrients, and 12 layers of nonwoven geotextile fabrics; and PRB-3 consisted of only sand and gravel as reactor media (natural attenuation—NA). This study was conducted to assess the impact of geotextile fabric filter, bioaugmentation, and biostimulation on toluene degradation efficiency. After 167 days of treatment, toluene biodegradation efficiencies varied between 88.2% and 93.8% for PRB 1, between 98.0% and 99.3% for PRB 2, and between 14.2% and 68.6% for PRB 3. The effluent toluene concentrations for PRB-2 were less than the guideline value (0.7 mg/L) of the World Health Organization. Reaction rate data were fitted with a first-order kinetic reaction rate model. This study showed that the toluene removal efficiency in the geotextile layered PRB combined with BA and BS process was significantly higher compared to the other processes tested. This lab-scale study introduced a new PRB configuration suitable for the remediation of sites contaminated with toluene.

The study of Cu/Fe-doped Al-MCM-41 to degrade Rhodamine B.

Textile wastewater has been recognized as one of the most difficult to treat environmental problems. Aiming to acquire an excellent treatment effect that could meet the stringent discharge regulations, a series of Cu- and Fe-doped Al-MCM-41 heterogeneous Fenton catalysts with different metal contents (1.21-3.45 wt%) were successfully synthesized by co-precipitation method to degrade Rhodamine B. Their physicochemical properties were analysed by X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, nitrogen physisorption and scanning electron microscopy. The incorporation of metal did not alter MCM-41's mesostructure, but increasing the contents of metal would decrease the order of MCM-41s' structure. The effects of temperature, pH, H2O2 dosage, dye concentration and the dosage of catalysts on Rhodamine B degradation were also investigated. It was found that M2 with 2.71 wt% of active metals performed best on Rhodamine B degradation. For the high concentration of Rhodamine B (400 mg/L), the decolorization efficiency could reach 96.0% using only 40 mM H2O2 within 50 min at 60 °C. Further adding 40 mM of H2O2, the chemical oxygen demand removal reached 75.1% after 100 min. M2 showed excellent stability and could be reused at least three times without any obvious deterioration in catalytic activity. M2 fitted well with the Freundlich isotherms and the first-order rate model.

An optimal charging algorithm to minimise solid electrolyte interface layer in lithium-ion battery

This article presents a novel control algorithm for online optimal charging of lithium-ion battery by explicitly incorporating degradation mechanism into control, to reduce the degradation process. The health of battery directly relates to degradation and capacity fade in cycles of charging. We mainly focus on the growth of the solid electrolyte interface (SEI) layer, which is the primary source of degradation of batteries. This article addresses the challenge of minimising SEI layer growth during charging by incorporating the first-order SEI layer growth rate model into a non-linear model predictive control approach. A single particle model (SPM) is used for optimal charging using orthogonal projection-based model reformulation. Gauss pseudo-spectral method is used for the optimisation of charging trajectories. Results of the optimal algorithm are compared with the traditional constant current constant voltage (CCCV) approach without considering SEI layer growth. It is ensured that overpotential caused by lithium plating remains in a healthy regime which is another feature of the proposed strategy. Simulation results are presented to demonstrate the advantages of the proposed charging method.

Performance and Kinetics of Bioaugmentation, Biostimulation, and Natural Attenuation Processes for Bioremediation of Crude Oil-Contaminated Soils

Bioremediation of contaminated sites is usually limited due to the inadequate availability of nutrients and microorganisms. This study was conducted to assess the impact of bioaugmentation (BA) and biostimulation (BS) on petroleum hydrocarbon degradation efficiency. In addition, treatment performance and kinetics of different remediation processes were investigated. For this purpose, four tanks containing oil-contaminated soils were tested. Tank 1 was operated as the natural attenuation process. Then, a microbial inoculum and nutrients were added to tank 2 to promote BA and BS. In tank 3, only the BA process was adopted, whereas in tank 4, only the BS process was adopted. After 63 days of operation, the total petroleum hydrocarbon (TPH) in tank 2 was reduced from 1674 to 430 mg/kg, with 74% reduction. Tank 1, tank 3, and tank 4 indicated TPH reductions of 35%, 41%, and 66%, respectively. Microbiological analysis of the inoculum indicated that Alcanivorax was the dominant bacterium. The population of TPH degrader bacteria in tank 2 soil was two orders of magnitude higher than in the control tank. Reaction rate data were fitted with a first-order reaction rate model. The Monod kinetic constants, maximum specific growth rate (µmax), and substrate concentration at half-velocity constant (Ks) were also estimated. This study showed that the TPH removal efficiency in the combined BA and BS process was higher than in other processes tested. The populations of TPH degrading microorganisms in soil tanks were positively related to TPH removal efficiency during bioremediation of petroleum-contaminated soils.

Optimization of substrate composition in anaerobic co-digestion of agricultural waste using central composite design

Biochemical methane potential (BMP) tests and modelling of anaerobic co-digestion (AcoD) of ternary mixtures of agricultural waste, i.e., sugar beet root waste (BW), cow dung (CD), and poultry manure (PM), are presented. According to a two-factor central composite design (CCD), 12 BMP tests were conducted under mesophilic conditions for 30 days (d). CD mass fraction (0.146–0.854) in the animal manure mixture and C/N ratio (13.515–30.485) of ternary waste mixture were selected as process factors. Experimental values of ultimate cumulative methane yield as process response were in the range of 105.32–356.10 mL/g VS. A first-order rate model was applied to predict the process kinetics. Enhanced values of methane production rate, evaluated as rate constant (0.044–0.123 d−1), were obtained for lower levels of CD mass fraction and higher levels of C/N ratio. Response surface methodology (RSM) was applied to assess the effects of process factors on the response and to find the optimum factor levels leading to a maximum performance. A maximum value of response variable of 347.48 mL/g VS was predicted for a CD fraction of 0.323 and a C/N ratio of 26.24. Values of experimental ultimate methane yield of 358.45 ± 33.40 mL/g VS, obtained in the BMP tests at optimum levels of process factors, were close to that of the maximum response predicted by the statistical model, demonstrating the model validity. Moreover, a significant synergistic effect (an increase in methane yield by 41.2%) related to the weighed experimental BMP of substrate mixture was obtained under optimum conditions.

Assessing and Modelling the Efficacy of Lemna paucicostata for the Phytoremediation of Petroleum Hydrocarbons in Crude Oil-Contaminated Wetlands

The potentials of the invasive duckweed species, Lemna paucicostata to remove pollutants from aquatic environment was tested in a constructed wetlands as an ecological based system for the phytoremediation of petroleum hydrocarbons in crude oil-contaminated waters within 120 days. Total petroleum hydrocarbons in wetlands and tissues of duckweed were analyzed using gas chromatography with flame ionization detector following established methods while the experimental data were subjected to the first-order kinetic rate model to understand the remediation rate of duckweed in wetlands. L. paucicostata effected a significant (F = 253.405, P < 0.05) removal of hydrocarbons from wetlands reaching 97.91% after 120 days. Assessment on the transport and fate of hydrocarbons in duckweed indicated that L. paucicostata bioaccumulated less than 1% and significantly biodegraded 97.74% of hydrocarbons in wetlands at the end of the study. The experimental data reasonably fitted (r2 = 0.938) into the first-order kinetic rate model. From the result of the study, it is reasonable to infer that L. paucicostata is an effective aquatic macrophyte for the removal of petroleum hydrocarbons in moderately polluted waters.

Modification of geopolymer with size controlled TiO2 nanoparticle for enhanced durability and catalytic dye degradation under UV light

Geopolymer- a silica alumina-based polymer has attracted generous amount of interest since the last decades as a promising alternative binder to ordinary Portland cement (OPC) in the construction sector. Proper utilization of industrial waste (Fly ash) and their functionality enhancement is explored in the present exertion by incorporating titanium oxide (TiO2) nanoparticle with different size in it. Along with the development of advanced building composite photocatalytic ability of the synthesized product was also assessed. Rutile phase TiO2 NPs were synthesized hydrothermally and annealed at different temperatures which result in differences in their overall size. Different materials characterization techniques have been carried out for confirmation of phase, functional bond, binding energy, and morphology respectively. Geopolymeric (GT) composites (GT30, GT50, and GT100) were prepared at ambient temperature using this size-variant TiO2 NPs in fly ash and alkali activator. Integration of TiO2 nanoparticles (5%) enhances mechanical properties where the optimized composite GT30 shows the maximum compressive (53.59 MPa) and tensile strength (6.8 MPa). Mercury Intrusion porosimetry (MIP) and atomic force microscope (AFM) studies indicate that TiO2 nanoparticles of 30 nm (T30 NPs) reduce porosity and roughness of the structure, thus lead to densified matrix and high durability performances. Additionally, GT30 mortar has low water absorption capacity as T30 NPs decrease the apparent volume of permeable voids in its matrix. Degradation of Methylene Blue (MB), a model contaminant was investigated under ultraviolet (UV) light illumination. T30 NPs (1 mg) and GT30 (5 mg) are found to degrade >95% dye solution within 90 min towing to the high surface area of TiO2 NPs and free radical generation. Such outcomes are well fitted in the Langmuir–Hinshelwood first-order rate model. These results will pave the way to explore industrial waste; fly ash in geopolymer for the excellent durability and wastewater treatment through dye degradation under UV light illumination with the aid of TiO2 NPs.

Isotherms, thermodynamics and kinetics of methane-shale adsorption pair under supercritical condition: Implications for understanding the nature of shale gas adsorption process

This research article selects supercritical methane and organic-rich shale as adsorbate-adsorbent pair to investigate methane adsorption behavior and enrich our understanding of the nature of shale gas adsorption process. The isotherms and kinetics of methane-shale adsorption pair are measured at temperatures of 303 K, 323 K, 343 K and 363 K by using a volumetric experimental setup. Then, the Langmuir-based (Langmuir, Langmuir + k, Langmuir + Henry), BET-based (BET, BET + k, BET + Henry) and DA-based (DA, DA + k and DA + Henry) excess models are used to interpret measured excess isotherms, and the Unipore Diffusion (UD), Bidisperse Diffusion (BD) and Two Combined First-Order Rate (TCFOR) models are used to interpret the adsorption kinetics data. Instead of using the coefficient of determination (R2), this work used the corrected Akaike’s Information Criterion (AICc) for model selection. It is found that the DA + Henry model is more suitable for excess adsorption isotherms, and the TCFOR model is more appropriate for adsorption kinetics study. Additionally, for methane-shale adsorption under supercritical condition, the fugacity is of great significance in evaluating thermodynamic properties including isosteric heat of adsorption (qst), enthalpy change (ΔH), entropy change (ΔS) and Gibbs free energy change (ΔG). These properties show strong dependence on adsorption amount and temperature, and suggest that supercritical methane adsorption on organic-rich shale is a process of physisorption, exothermic and spontaneous. Further, the kinetics parameters extracted from kinetics curves suggest that the methane adsorption at each pressure step is a two-stage process, with a fast macropore diffusion process at early time, followed by a slow micropore diffusion process at later time. Additionally, the fast macropore diffusion dominates the two-stage adsorption process at lower pressures, while at higher pressures slow micropore diffusion dominates.

Methane production kinetics of pretreated slaughterhouse wastewater

The aim of this work was to analyze the methane production kinetics of pretreated slaughterhouse wastewater through biochemical methane potential (BMP) tests, where the volumetric ratio and, consequently, the substrate to inoculum ratio (SIR) were varied. The thermal pretreatment was autoclaving (60 min at 120∘C/1.2 atm), and two phases appeared: liquid (clarified) and semisolid. Half of this semisolid also underwent a mechanical pretreatment (1 min with a cell disruptor). Afterward, BMP tests were carried out in serological bottles under five different volumetric ratios (1:1, 2:1, 3:1, 4:1 and 5:1), with RSWW, semisolid and semisolid after mechanical pretreatment as substrates. The volume of clarified liquid obtained after autoclaving was 84.5% of the RSWW, with removal percentages of COD, solids, proteins, and ammonium ranging from 50% to 89%, while the volume of the semisolid was only 4.35% of the RSWW, with the major portion of the pollutants concentrated in it. In the BMP tests, the methane generation was approximately fifteen times higher and lasted two times longer with semisolid as the substrate than that when using RSWW. The optimal volumetric ratio was 4:1 (SIR 5.67). The methane kinetics also changed: in RSWW, the kinetics followed the typical sigmoidal curve, whereas in semisolid, the kinetics were complex, showing a stepped curve. The cumulative methane production fit well to the Gompertz, Richards, logistic, Luedeking-Piret and modified first-order rate models, although none of them accurately described the second inflection point found at the end of the inhibited steady-state phase.

Dual-responsive (pH/temperature) Pluronic F-127 hydrogel drug delivery system for textile-based transdermal therapy

A dual-responsive hydrogel (pH/temperature) was developed from a thermos-responsive polymer, pluronic F-127 (PF127), and pH-responsive polymers, N,N,N-trimethyl chitosan (TMC) and polyethylene glycolated hyaluronic acid (PEG-HA). Gallic acid, the principal component of the traditional Chinese drug Cortex Moutan was loaded into the hydrogel (PF127/TMC/PEG-HA) for possible application in textile-based transdermal therapy as Cortex Moutan has been proven to be an effective drug for the treatment of atopic dermatitis (AD). TMC and PEG-HA were synthesized, characterized (1H-NMR and FTIR), and added to the formulations to enhance drug release from the hydrogels, and increase the drug targeting of the carriers. The thermo-responsive properties of the hydrogel were assessed by dynamic viscosity analysis and the tube inversion method, and the pH-responsiveness of the formulation was determined by changing the pH of the external media. Rheology study of the hydrogels showed that complex viscosity and storage/loss moduli for PF127/TMC/PEG-HA hydrogel formulation are higher than PF127 hydrogel. The microstructure analysis by reflection SAXS indicated similar type of frozen inhomogeneity of hydrogel formulations. Various characterizations such as FTIR, SEM, TEM, zeta potential, and degradation of the hydrogel formulation indicated that the PF127/TMC/PEG-HA hydrogel showed better physico-chemical properties and morphology than did the PF127 hydrogel, and drug release was also higher for the PF127/TMC/PEG-HA hydrogel than for PF127. The drug release from hydrogels followed more closely first-order rate model than other rate models.