Optimum Initial Concentration Research Articles

Green ferrites nanoparticles synthesis using Aloe vera and watermelon rinds: their applications as sorbents in the purification of direct golden yellow RL dye wastewater

ABSTRACT The sorbents Ni-Cu-FNP’s, Ni-Zn-FNP’s, Mn-FNP’s, and Zn-FNP’s were synthesised and utilised for the removal of Direct Golden Yellow RL dye. The optimum pH for the adsorption of direct golden yellow RL dye was 4, and 3 having the sorption capacities of 32.56, 30.44, 34.39, and 36.91 mgg−1 for Ni-Cu-FNP’s, Ni-Zn-FNP’s at 45 min and Mn-FNP’s, Zn-FNP’s at 60 min respectively with the optimum dosage of 0.05 g/50 mL. The maximum sorption capacities were 39.08 (Ni-Cu-FNP’s), 35.08 (Ni-Zn-FNP’s), 42.93 (Mn-FNP’s), and 44.22 mg/g (Zn-FNP’s) at 40°C, 37°C, 44°C, and 44°C respectively and the reduction observed in the sorption capacity by raising the temperature, showed that the process is exothermic The optimal initial concentration of dyes for all the sorbents having the maximum sorption capacities of 54.30 mg/g (Ni-Cu-FNP’s), 51.25 mg/g (Ni-Zn-FNP’s), 63.45 mg/g (Mn-FNP’s), and 66.35 mg/g (Zn-FNP’s) were 75, 100, 100, and 75 mg/L respectively to get maximal acidic dyes adsorption. Langmuir equilibrium isotherm for sorption showed good fitness on the data obtained by sorption while the pseudo-2nd-order proved good fitness on kinetic data of experiments. Surfactants, detergents, and different molar solutions of electrolytes (NaCl and AlCl3) decreased the sorption capabilities of the sorbents for the selected dye.

An improved Eulerian scheme for calculating proppant transport in a field-scale fracture for slickwater treatment

Field-scale proppant transport simulation is vital to the development of unconventional resources. Previous research on proppant transport and distribution has mainly focused on small-scale and experimental-scale proppant simulations, and few studies are related to field-scale proppant deployment. In this paper, through coupling of the slickwater flow, proppant flow, and dynamic crack propagation, an improved Eulerian scheme for calculating proppant transport in a field-scale fracture for slickwater treatment is presented. In the improved Eulerian scheme, the effect of the fracture width on the proppant settling rate and the effect of the increase in the settling bed height on the proppant bed build-up rate are taken into consideration. In addition, a new retardation coefficient is introduced to account for the effect of proppant retardation on the proppant flow. The Eulerian scheme is verified through comparison with published works, including experimental results and simulation results, and sensitivity analysis is conducted. Based on the results of this research, we conclude that the lower viscosity slickwater causes the proppant distribution to become more even, and thus, the proppant bed becomes longer and higher. As the proppant diameter increases, the proppant distribution in the fracture becomes more even, and the fracture area supported by the proppant becomes larger. The optimal initial proppant concentration for obtaining the largest propped fracture area is 0.15–0.25. The greater the density of the slickwater is, the more even the proppant distribution is, and the larger the propped fracture area is.

Effects of nitrate concentrations on As(III) immobilization via new ferric arsenite hydroxynitrate precipitates

The Fe(III)-As(III)-anion precipitation as layered double hydroxide-like compounds such as tooeleite and ferric arsenite hydroxychloride (FC) has been found in As(III)-contaminated acidic mine soils. However, the question of whether As(III) is immobilized by Fe(III) in aqueous nitrate media, a common constituent in soils and metallurgical wastewater, remains unclear. Herein, we investigated the effects and mechanism of nitrate on As(III) immobilization via Fe(III)-As(III)-nitrate precipitation. Our results indicated that new ferric arsenite hydroxynitrate (FN) with variable Fe(III)/As(III)/nitrate molar ratios crystallized in an initial nitrate content range of 11,160–74,400 mg·L−1 at pH 2.3. This FN precipitation resulted in 60.3–87.9% of As(III) removal and a fall-rise immobilization trend as a function of the initial nitrate concentration. The optimal initial nitrate concentration for As(III) fixation was 44,640 mg·L−1. Although FN shared similar morphology and crystal structure with tooeleite and FC, the substitution of NO3− for SO42− and Cl− in the FeO6-AsO3 interlayers caused a significant local structural distortion due to different ionic radii. The characteristic infrared and Raman bands of the nitrate group in FN occurred at 1,363 cm−1, 1,384 cm−1 and 152 cm−1, 722 cm−1, 1,055 cm−1, respectively. The FN induced significantly enhanced As(III) immobilization relative to its tooeleite and FC counterparts at equimolar concentrations of NO3−, SO42−, and Cl− as the media.

Biodegradation of the nitrile-containing insecticides sulfoxaflor, flonicamid, thiacloprid, and acetamiprid by immobilized Escherichia coli harboring genes of nitrile hydratase and a cobalt transporter

The nitrile-containing insecticides sulfoxaflor, flonicamid, thiacloprid, and acetamiprid are used widely in agriculture, polluting the environment and harming animals. The Co2+-dependent enzyme nitrile hydratase (NHase) is a powerful tool for the degradation of nitrile-containing insecticides. Here, the NHase activities of Escherichia coli pET28a-PsNHase, harboring Pseudomonas stutzeri CGMCC 22915 (Ps) NHase gene, and E. coli pET28a-PsNHase-PsCbiM, harboring genes of PsNHase and a cobalt transporter PsCbiM, were compared. The presence of PsCbiM promoted PsNHase activity. E. coli pET28a-PsNHase-PsCbiM was immobilized using calcium alginate, which increased the tolerance of its NHase to acidic, alkaline, and high-temperature environments. Immobilized E. coli pET28a-PsNHase-PsCbiM was applied to degrade sulfoxaflor, flonicamid, thiacloprid, and acetamiprid. These insecticides were both substrates and inhibitors of immobilized E. coli pET28a-PsNHase-PsCbiM. Substrate inhibition model assays showed that the optimum initial concentrations of sulfoxaflor, flonicamid, thiacloprid, and acetamiprid for degradation by immobilized cells were 455.01, 195.50, 139.20, and 410.26 μmol/L, respectively. Degradation of nitrile-containing insecticides by immobilized engineered E. coli cells was reported here for the first time. This study provides a novel and excellent bioremediation agent for treatment of wastewater contaminated with nitrile-containing insecticides.

Algorithm for Optimizing the Initial Conditions for a Chemical Reaction Based on a Kinetic Model

A numerical algorithm has been developed to search for the optimal values of the concentrations of chemical reaction reagents. The statement of the problem of determining the optimal initial concentrations of the initial substances on the basis of the kinetic model of the reaction, which is a system of ordinary differential equations, is formulated. To solve the problem, a genetic algorithm with real coding is given. The algorithm is modified taking into account the restriction on the values of the initial concentrations and the condition imposed on the total initial concentration of the reagents. A computational experiment was carried out for the reaction of the synthesis of benzyl butyl ether under the action of copper-containing catalysts. The initial concentrations of the initial substances are determined at which the highest values of the concentrations of the target reaction products are achieved.

Removal of Tetracycline from aqueous solution using composite adsorbent of ZnAl layered double hydroxide and bagasse biochar

A new composite adsorbent of biochar derived from bagasse and ZnAl-layered double hydroxide was produced by the in-situ growth method. The prepared biochars were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) analysis, the Brunauer–Emmett–Teller (BET) isotherms, Scanning electron microscopy (SEM), Energy Disperse X-ray (EDX) spectroscopic and Mular–Roberts titration analyses. The best Zn:Al molar ratio for the ZnAl-LDH/BGC composite to adsorb tetracycline was 3:1. The specific surface area of ZnAl-LDH/BGC31 was 456.39 m 2 /g compared to 404.05 m 2 /g for BGC. The optimal pH, contact time and initial TC concentration for TC adsorption were 6.0, 120 min and 25 mg/L, respectively. The ZnAl-LDH/BGC31 had a maximum adsorption capacity ( q m ) of 41.98 mg/g. The obtained data were analyzed with Langmuir, Freundlich and Tempkin isotherm models. Kinetic data were evaluated by using pseudo-first and pseudo-second-order kinetic models. The adsorption mechanism of ZnAl-LDH/BGC31 to remove TC was likely based on the pore-filling process, electrostatic attraction and π − π conjugate effect. ZnAl-LDH/BGC31 had significant adsorption capacity after five reusabilities. • ZnAl-layered double hydroxide bagasse biochar compositered (ZnAl-LDH/BGC31) was synthesized. • The maximum adsorption capacity ( q m ) of TC (41.98 mg/g) at pH 6 and 25 mg/L of initial TC. • Isotherm and kinetic model fitting indicated physisorption and chemisorption of TC. • The pore-filling process, electrostatic attraction and π − π conjugate effect were critical role in TC adsorption. • ZnAl-LDH/BGC31 adsorbent maintained its high adsorption ability up to 5 reusability.

The Effect of Iodine-125 Radioactive Particle Stent with Doxorubicin-loaded Nano-tetrahedrons Combined with Transarterial Chemoembolization on Survival and Prognosis of Patients with Cholangiocarcinoma.

This study was to analyze the application of doxorubicin-loaded DNA nano-tetrahedral Iodine-125 (I-125) radioactive particle stent (doxorubicin-loaded 125I stent) combined with transarterial chemoembolization (TACE) in improving the prognosis of patients with cholangiocarcinoma (CC). The doxorubicin-loaded DNA nano-tetrahedrons were constructed, the preparation plan was optimized, and the toxicity test was performed. The prepared doxorubicin-loaded DNA nano-tetrahedrons were applied to 85 cases in the K1 group (doxorubicin-loaded 125I + TACE), 85 cases in the K2 group (doxorubicin-loaded 125I), and 85 cases in K3 group (TACE). It was found that the optimal initial concentration of doxorubicin for the preparation of DNA-loaded nano-tetrahedrons was 200 mmol, and the optimal reaction time was 7 hours. The serum total bilirubin (TBIL) level in the K1 group at 30 days after operation was lower than that in the K2 and K3 groups at 7, 14 and 21 days. (P< 0.05). The alkaline phosphatase (ALP) level in the K1 group was lower in contrast to that in the other two groups at 7, 14, and 21 days after surgery (P< 0.05); and the five-year survival rate of patients in the K1 group was greater in contrast to the rate in K2 and K3 groups (P< 0.05). In short, the implantation of a doxorubicin-loaded 125I stent combined with TACE could effectively improve the five-year survival rate of patients with CC and improve the prognosis effect of the patients.

Fabrication and evaluation of a photocatalytic membrane based on Sb2O3/CBO composite for improvement of dye removal efficiency

Methylene blue (MB) and Acid Blue 25 (AB 25) dyes are organic substances that are potentially harmful to humans and the environment. In this study, a photocatalytic membrane was fabricated based on Sb2O3/CuBi2O4 (Sb2O3/CBO) composite for the degradation of MB and AB 25 dyes under visible light irradiation. At the first, several significant parameters such as pH (2, 5, 7, 9, and 11), initial dye concentration (10, 30, 50, 60, and 75 ppm), and photocatalyst dosage (0.005, 0.0075, 0.01, and 0.02 g) were optimized by using Sb2O3/CBO composite under visible illumination in a batch system. Moreover, various characteristics of the as-synthesized materials were analyzed by FESEM, FTIR, XRD, PL, and UV–Vis DRS. Additionally, the continuous experiments were conducted with a hybrid of several percentages of produced nanoparticles and Polyethersulfone membrane to maximize the process efficiency. Results show that an increase in pH and catalyst dosage had a positive influence on dye degradation. Furthermore, the photocatalytic decolorization of MB in an alkaline solution was higher than that of the acidic solution and vice versa for AB 25. The optimum initial concentration and photocatalyst dose for both dye solutions were determined to be 10 ppm and 0.01 g, respectively, whereas the optimal pH values for AB 25 and MB were 2 and 11. The highest photocatalytic dye removal efficiency (94.6 percent) was obtained under optimal conditions using a 10% Sb2O3/CBO photocatalyst in the presence of a membrane.

Optimal loading of hydrogel-based drug-delivery systems

Drug-loaded hydrogels provide a means to deliver pharmaceutical agents to specific sites within the body at a controlled rate. The aim of this paper is to understand how controlled drug release can be achieved by tuning the initial distribution of drug molecules in a hydrogel. A mathematical model is presented for a spherical drug-loaded hydrogel. The model captures the nonlinear elasticity of the polymer network and thermodynamics of swelling. By assuming that the drug molecules are dilute, the equations for hydrogel swelling and drug transport partially decouple. A fast optimisation method is developed to accurately compute the optimal initial drug concentration by minimising the error between the numerical drug-release profile and a target profile. By taking the target drug efflux to be piecewise constant, the optimal initial configuration consists of a central drug-loaded core with isolated drug packets near the free boundary of the hydrogel. The optimal initial drug concentration is highly effective at mitigating the burst effect, where a large amount of drug is rapidly released into the environment. The hydrogel stiffness can be used to further tune the rate of drug release. Although stiffer gels lead to less swelling and hence reduce the drug diffusivity, the drug-release kinetics are faster than for soft gels due to the decreased distance that drug molecules must travel to reach the free surface.

Textile dyeing wastewater treatment by Penicillium chrysogenum: Design of a sustainable process.

In this work a parametric study and a bench bioreactor degradation test of Direct Black 22 (DB22) by Penicillium chrysogenum was performed as a first approach to an industrial application, framed within a policy of sustainable processes development. Three ancillary carbon sources and their optimum initial concentrations were studied. These were: glucose, potato starch and potato industry wastewater. Their optimum initial concentration was 6 g/L. The use of potato starch as co-substrate showed the highest decolorization rate and COD removal. Degradation of DB22 using different immobilization supports (stainless steel sponge, loofah sponge and polyethylene strips) was studied and the results showed that the time needed for the treatment decreased from 6 to 4 d. Phytotoxicity was evaluated in the final products of the immobilized cells assays, using Lactuca sativa seeds. For all treatments phytoxicity was reduced with respect to the untreated wastewater, except for the assays using polyethylene strips. Finally, the reuse of the biomass attached to different carriers and the performance of the treatment of DB22 in a 1 L bench scale bioreactor were tested. P. chrysogenum decolorized at least four sucesives reuses. The reactor assays showed a better performance of the treatment.

Producing Natural Flavours from Isoamyl Alcohol and Fusel Oil by Using Immobilised Rhizopus oryzae Lipase

Enzymatic synthesis of short-chain esters (flavours) might enable their labelling as natural, increasing their value. Covalently immobilised Rhizopus oryzae lipase (EO-proROL) was used to synthesise isoamyl butyrate and acetate. In cyclohexane, the best performer reaction solvent, 1.8 times higher yield of isoamyl butyrate (ca. 100%) than isoamyl acetate (ca. 55%) was obtained. Optimum initial acid concentration (410 mM) and acid:alcohol mole ratio (0.5) were established by a central composite rotatable design to maximise isoamyl butyrate single-batch and cumulative production with reused enzyme. These conditions were used to scale up the esterification (150 mL) and to assess yield, initial esterification rate, productivity and enzyme operational stability. Commercial isoamyl alcohol and fusel oil results were found to be similar as regards yield (91% vs. 84%), initial reaction rate (5.4 µM min−1 with both substrates), operational stability (40% activity loss after five runs with both) and productivity (31.09 vs. 28.7 mM h−1). EO-proROL specificity for the structural isomers of isoamyl alcohol was also evaluated. Thus, a successful biocatalyst and product conditions ready to be used for isoamyl ester industrial production are here proposed.

Adsorption of 4-Nitrophenol onto Iron Oxide Bentonite Nanocomposite: Process Optimization, Kinetics, Isotherms and Mechanism

Despite its importance in chemical industry, 4-Nitrophenol (4-NP) is a persistent organic pollutant that has serious effects on the ecosystem. In the present study, Box–Behnken design in response surface methodology was used to optimize the adsorption process parameters for the maximum 4-NP removal at 30 ℃ using Fe3O4/Bt NC. The regression model results suggested that the optimum adsorbent dosage, initial concentration, pH and contact time were 0.3182 g, 85 mg/L, 11 and 137.2 min, respectively. The regression model showed an optimum removal of 100%, while 99.5% removal was obtained from batch experiments at the optimum conditions suggested by the regression model, which confirm the model validity. The adsorption data best fitted to Freundlich isotherm model and Pseudo second-order kinetic model suggesting the existence of physical and chemical interaction between the fabricated composite and 4-NP. FTIR analysis suggested that the adsorption mechanism included an electrostatic attraction and the formation of new chemical bonds. Obtained results suggest that Fe3O4/Bt NC can be an effective adsorbent for complete 4-NP removal at the indicated optimum conditions.Graphical

Evaluation of Scales of Tilapia Sp. and Sciaenops ocellatus as Low Cost and Green Adsorbent for fluoride Removal From Water.

Water containing more than 1.5 mg/L of fluoride is considered toxic as it causes dental, kidney, and other health problems. With the purpose of helping alleviate these problems by exploring a treatment method for fluoride contamination, this study was to assess the suitability of scales of Tilapia Sp. and Sciaenops ocellatus as a cheaper source of adsorbent for the removal of fluoride from drinking water. The samples which were obtained from the Lapaz Market in Accra, Ghana, underwent treatment to eliminate any impurities. They were then ground into powder and treated with aluminum hydroxide [Al(OH)3]. The treated samples were used for the removal of fluoride from spiked solutions prepared in the laboratory. Batch adsorption was performed by varying parameters such as adsorbent dose (1–8 g/L), initial concentration (2 mg/L to 10 mg/L), and contact time (30–300 min) at pH of 7. A one-way ANOVA was used to validate the significance of the defluoridation process with respect to the different experimental conditions. The optimum adsorbent dose, initial concentration, and contact time were found to be 4 g/L, 10 mg/L, and 300 min, respectively. The results revealed that the maximum percentage removal of fluoride was 76% by Tilapia Sp. and 70% by Sciaenops ocellatus at the optimum conditions. This is an indication that both Tilapia Sp. And Sciaenops ocellatus scales are suitable adsorbents for the removal of fluoride from water. The fluoride adsorption kinetics followed the pseudo-second-order model, and the adsorption isotherm fitted the Freundlich Isotherm model better than the Langmuir Isotherm model. The adsorption intensity and adsorption capacity for Tilapia Sp. were 3.484 L/mg and 0.065 mg/g, and that of Sciaenops ocellatus 3.195 L/mg and 0.045 mg/g respectively.

Effects of enzymatic hydrolysis and alkalization pretreatment on biohydrogen production by chlorella photosynthesis

The effects of alkalization pretreatment and enzymolysis on biohydrogen production with Chlorella vulgaris microalgae biomass by photosynthesis were studied, the alkalization pretreatment enzymolysis was to alkalize biomass raw materials before enzymolysis, the biohydrogen production kinetics equation of microalgae biomass was put forward by comparing the biohydrogen process of enzymatic hydrolysis with that of alkaline pretreatment enzymatic hydrolysis. The experimental results show: the optimum initial substrate concentration for biohydrogen production by enzymatic hydrolysis and alkaline pretreatment was 24 g/L, the maximum biohydrogen was 132.1 mL and 294.5 mL, the maximum specific biohydrogen production was 22.0 mL/g and 49.1 mL/g, and the maximum biohydrogen content was 43.9% and 56.8%. The effect of biohydrogen production by enzymatic hydrolysis after alkaline pretreatment of microalgae biomass is obviously better than that by direct enzymatic hydrolysis, which provides scientific reference and development of high efficiency and low cost biohydrogen production technology by photosynthesis of microalgae biomass.

Enhanced oxidative activation of chlorine dioxide by divalent manganese ion for efficient removal of PAHs in industrial soil

Chlorine dioxide (ClO2) takes effect as a promising chemical oxidant to remove polycyclic aromatic hydrocarbons (PAHs) from contaminated soil in situ. However, the conventional ClO2 degradation procedure is limited by its reaction selectivity to organic pollutants, as well as its low economic efficiency with huge dosage. Systematical study of activated ClO2 oxidation which is more efficient to remove PAHs in soil is still scarce. Herein, the impact of divalent manganese ion [Mn(Ⅱ)] on activating ClO2 to oxidize PAHs in real contaminated soil was currently studied, including the kinetics, degradation products, mechanisms, and biological toxicity. The results revealed that the PAHs removal rate constants (k1) had a quadratic relationship with Mn(II) concentrations (k1 = -0.005 × [Mn(Ⅱ)]2 + 0.0033 × [Mn(Ⅱ)] + 0.0222, R2 = 0.9084, [Mn(Ⅱ)] = 0 ∼ 5 mM), the best degradation performance was obtained when the molar ratio of Mn(II)/ClO2 was 1/20. Furthermore, the optimal initial ClO2 concentration of 2500 mg/L could satisfy the comprehensive considerations of efficiency and economy. At the pH range of 3 ∼ 11, the removal efficiency decreased with increasing pH. Four representative PAH congeners (anthracene, phenanthrene, pyrene, and fluoranthene) had been chlorine substituted and oxygenated, but benzene ring rupture was observed only in fluoranthene simultaneously. XPS spectra, EPR analysis, and quenching experiments indicated the mechanisms that HOCl and •OH were the principal active species in the oxidation reaction. The toxicity evaluation by earthworms Eisenia fetida resulted out that high toxic effect to organism still remained in remediated soil which should be paid attention to.

Synthesis, antibacterial activity and adsorption studies of Bentonite-iron nanoparticles in the removal of methyl blue dye

Green synthesis of bentonite-iron nanoparticles (Be-FeNPs) has been carried out using the leaf extract of Helicteres isora and its antibacterial and adsorption capacity for the removal of Methyl Blue (MB) dye have been also studied.T he prepared Be-FeNPs and iron nanoparticles (FeNPs) are characterized by UV-visible, FTIR spectroscopic techniques and SEM analysis. The antibacterial activity of Be-FeNPs show good zone of inhibition against E.coli and S.aureus. Further the prepared composite (Be-FeNPs) and bentonite are used as adsorbents for the removal of Methyl Blue (MB) dye in aqueous solution under various experiment parameters like initial concentration, contact time and pH. The optimum initial pH, adsorbent concentration and time were determined to be 8.1, 45°C, and 100 ppm, 80 min for MB adsorption on to Be-FeNPs. The experimental data for MB adsorption fits well to the Freundlich and Langmuir isotherm models. The kinetic equations like Natarajan-Khalaf, Bhattacharya-Venkobachar and Lagergren equations were found to be applicable. The surface morphology of the Be-FeNPs before and after adsorption of dye revealed that it can be used as an excellent adsorbent for dye removal from dilute industrial effluents.

The formation of structure I hydrate in presence of n-octyl-β-D-glucopyranoside

A new promoter for hydrate-based technologies (HBTs) called n-octyl-β-D-glucopyranoside (OGP) was proposed in this work. The effect of OGP on the properties of liquid phase, the thermodynamic effect of OGP on structure I hydrate (formed by ethylene and water) and the effect of OGP on the formation process of structure I hydrate were investigated. To determine the controlling factors of the hydrate formations, a new model which can accurately predict the thermodynamic equilibrium hydrate formation pressures of corresponding systems was proposed, and the average relative deviation of the model is 1.6%. The experimental results show that, OGP was a low foaming promoter with high surface activity, and OGP rarely affected the thermodynamic phase equilibria of corresponding systems. OGP not only significantly increased the hydrate formation rate (rR) but also increased the conversion rate of the water into hydrate (RWH) from about 61.2% to about 95.5%, and the maximum RWH of the ethylene gas-OGP solution system in this work was 97.5 ± 1.6%. The optimum initial OGP concentration for HBTs was 0.2 mass%. The difference in rR caused by the difference in pressure significantly decreased as RWH increased from 10% to 40%. rR did not significantly decrease during the period that RWH increased from 40% to 65%, and the steady rR during that period benefits the application of HBTs.

Sulfide-driven nitrous oxide recovery during the mixotrophic denitrification process

We propose a novel sulfide-driven process to recover N2O during the traditional denitrification process. The optimum initial sulfide concentration was 120 mg/L, and the N2O percentage in the gaseous products (N2O+N2) was up to 82.9%. Moreover, sulfide involved in denitrification processes could substitute for organic carbon as an electron donor, e.g., 1 g sulfide was equivalent to 0.5-2 g COD when sulfide was oxidized to sulfur and sulfate. The accumulation of N2O was mainly due to the inhibiting effect of sulfide on nitrous oxide reductase (N2OR), which was induced by the supply insufficiency of electrons from cytochrome c (cyt c) to N2OR. When the initial sulfide concentration was 120 mg/L, the N2OR activity was only 36.8% of its original level. According to the results of cyclic voltammetry, circular dichroism spectra and fluorescence spectra, significant changes in the conformations and protein structures of cyt c were caused by sulfide, and cyt c completely lost its electron transport capacity. This study provides a new concept for N2O recovery driven by sulfide in the denitrification process. In addition, the findings regarding the mechanism of the inhibition of N2OR activity have important implications both for reducing emissions of N2O and recovering N2O in the sulfide-driven denitrification process.

Investigation of competitive adsorption and desorption of heavy metals from aqueous solution using raw rock: Characterization kinetic, isotherm, and thermodynamic

This study consists to evaluate an efficient and eco-friendly pathway of competitive recovery of heavy metals (Cd (II), Cr, (VI), and As (III)) from aqueous solution using raw rock depending on different parameters including contact time, adsorbent mass, solution pH, temperature, and initial concentration of the metals. The contact time required for equilibrium was reached at about 30 min for As (III) and 45 min for Cd (II) and Cr (VI) at 25 °C. The retention of Cd (II), Cr (VI), and As (III) by CAQ was favorable to acidic pH between 2 and 3.5. However, the optimal initial concentration of the competitive removal metals was achieved at 70 mg/L using 0.5 g of CAQ. The adsorption kinetics of heavy metals were adapted to the pseudo-second-order model. The maximum experimental adsorption capacities predicted by the Langmuir model are 15.23 mg/g for Cd (II), 17.54 mg/g for Cr (VI), and 16.36 mg/g for As (III). The values of thermodynamic parameters revealed that the adsorption of heavy metals was exothermic, favorable, and spontaneous in nature. The desorption process of heavy metals showed that this raw rock has an excellent recycling capacity.

The synthesis of tannin-based graphene aerogel by hydrothermal treatment for removal of heavy metal ions

Tannin (complex polyphenol) is commonly obtained from the bark and fruits. Its ortho-phenolic hydroxyl groups can adsorb heavy metal ions from wastewater by chelation. However, the adsorption performance to heavy metals (especially Pb) of the tannin-based materials is unsatisfactory. Herein, the tannin-reduced graphene aerogel (TRGA) was prepared by a one-step method for Pb(II) and Cd(II) adsorption. Results indicated that TRGA with a three-dimensional porous structure, low density, large specific surface area (122.2 m2/g) and high porosity, can facilitate the adsorption of metal ions. The maximum Pb(II) adsorption capacity of TRGA reached 803.84 mg/g at pH 4, which was much higher than that of precious tannin based adsorbents. Besides, the maximum adsorption capacity for Cd(II) is 395.80 mg/g at pH 4 when the optimal initial concentration of Cd(II) is 160 mg/L. Overall, the high capability and large efficiency of TRGA display widespread potentials for heavy metals adsorption.