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Biomining through bioleaching and bio-oxidation aims at recovering desired metals at the required specifications with lower environmental impact and costs from ores and waste streams. Research and ...

The adhesion of microorganisms to surfaces and the affecting factors is important in biomining pretreatment. In this research, the novelty is focused on studying the monosaccharide's impact on the adaptability and adhesivity of Ferroplasma acidiphilum for oxidization of sulfide-bearing ore containing pyrite harboring 98 % of gold in its crystal lattice. d-sucrose increased EPS production with the highest amount of pyrite dissolution (69 %) as compared to the other types of monosaccharides (d-galactose and d-fructose). Addition of 0.8 wt% d-sucrose enhanced the production of ferric ions 65 % for the ore load of 20 wt% while for the addition of 0.4 wt%, the ferric ions concentration was maximum up to 95 %. The results indicated that the addition of both yeast extract and d-sucrose with the concentration of 0.4 wt% enhanced the EPS (Extracellular Polymeric Substances) biovolume fraction from 7.5 to 32.5 v/v %.

The co-metabolic biodegradation of p-xylene (as a non-growth substrate model) by Pseudomonas putida (well-known aromatic compounds degrading microorganism) in the presence of Benzene (B), Toluene (T), and Ethylbenzene (E) was studied. Michaelis-Menten/Monod kinetics coupled with co-metabolic degradation expression can be applied for systems containing one growth and one non-growth substrate; thus, the GMDH Group Method of Data Handling (GMDH) was proposed in this study to predict the co-metabolic transformation of non-growth substrates in the presence of more than one growth substrate. Thus, the GMDH Group Method of Data Handling (GMDH) was proposed for the first time to quantify p-xylene degradation (with

To prepare superabsorbent hydrogels, starch-graft-poly(acrylic acid) reinforced by cellulose nanofibers (CNF), was synthesized through free radical graft polymerization. The results of its biocompatibility tests exhibited that by increasing incubation time from 1 to 5 days, the numbers of living cells were increased on both reinforced and unreinforced hydrogels. However, the fraction of cells on the surfaces of the reinforced hydrogel is comparable to unreinforced samples. The swelling amounts in NaCl, CaCl2, and AlCl3 solutions were 193 ± 9, 110 ± 8, and 99 ± 7 (gwater/gabsorbent) for 5 wt% CNF-reinforced hydrogels and 109 ± 8, 62 ± 7, and 56 ± 6 (gwater/gabsorbent) for unreinforced hydrogels, respectively. Compressive strength and Young’s modulus of 5 wt% CNF-assisted hydrogels were also 63.3 and 31.6 kPa corresponding to 69% and 140% improvements compared with unreinforced one. The graft polymerization of acrylic acid monomer was controlled by monomer content and cross-linking percentage, in order to achieve the highest swelling capacity for hydrogels. Hydrogel swelling in water was 312 gwater/gabsorbent for unreinforced hydrogel and 523 gwater/gabsorbent for 5 wt% CNF-reinforced sample and water absorption kinetics results was in agreement with the pseudo-second-order model. The prepared CNF-reinforced starch-graft-poly(acrylic acid) hydrogels can be used in a wide range of medical application due to the enhanced hydrophilicity, mechanical strength, and biocompatibility.

In this research, a novel CoFe

This work evaluated a green route for developing an eco-friendly flowsheet to regenerate base and precious metals from waste printed circuits boards (WPCBs). Copper (as nanoparticles with an average diameter of 50 nm) and other base metals were extracted via oxidative acid leaching with high efficiency. Thiocyanate was employed for the first time as a green and economical reagent for the extraction of gold from pretreated WPCB. The effect of various parameters, including reagent dosage and temperature, was evaluated on the gold leaching rate, and 100% gold dissolution was achieved at the optimal condition. It was found that ferric iron concentration as the gold leaching oxidant has a notable effect on gold extraction. Also, at temperatures above room temperature, the recovery rate increases in a short period and then decreases continuously. The activation energy of the optimum gold thiocyanate leaching was found to be 42.84 kJ/mol, indicating chemical reaction to be the rate-controlling step. Gold extraction from the thiocyanate medium was carried out by employing activated carbon, where 100% gold adsorption was achieved in 2 h. Toxicity assessment of final residue revealed that it could be categorized as an environmentally safe waste with negligible risk.

Purpose A boiling surface with different initial roughness and under various nanoparticles volume fractions was studied in present work. Design/methodology/approach Develop a correlation and sensitivity analysis. Findings The results showed that for small (7.3 nm) and much larger (about 2,000 nm) surface roughness, compared to nanoparticle size of around 25 nm, the heat transfer rate of nanofluid diminishes relative to that of base fluid. The results also demonstrated that the boiling heat transfer rate is reduced by increasing the concentration of nanoparticles. For larger boiling surface roughness (480 nm) and nanoparticles volume fractions of less than 0.1 Vol.%, the value of heat transfer increases with the increase of nanoparticles concentration; and for those of more than 0.1 Vol.%, heat transfer rate decreases by adding more nanoparticles, significantly. Originality/value Finally, an equation was presented for estimating the wall superheat and the Csf coefficient in terms of mentioned parameters.

In this study, the impacts of temperature, nanoparticles mass fraction, and basefluid types were investigated on the dynamic viscosity of CuO-loaded nanofluids. The nanoparticles were dispersed in deionized water, ethanol, and ethylene glycol as basefluids separately and the measurements were performed on samples with nanoparticles loads ranging from 0.005 to 5 wt%, and the temperature range of 25 to 70 °C. TEM analysis were performed on dried nanoparticles and the results showed the average mean diameter of CuO nanoparticles ranged from 10 to 50 nm. The results of DLS analysis confirmed the results of nanoparticles size obtained by TEM analysis in mentioned basefluids and Zeta-Potential tests exhibited the high stability of the nanoparticles in the basefluids environment. The results indicate that by adding tiny amount of CuO nanoparticles to basefluids, relative viscosity of nanofluid increases. By the increase in nanoparticles load higher than 0.1 wt% the effect of both nanoparticles mass fraction and temperature would be more tangible, while for nanoparticles mass fraction lower than 0.1 wt% no significant change in viscosity was observed. In addition, the results declare that viscosity of nanofluid remains constant at various applied shear rates indicating Newtonian behavior of nanofluid at various nanoparticles load and temperature. According to experimental data, it is also evident that with the increase in temperature, the value of relative dynamic viscosity decreases significantly. Also it is concluded that for CuO/ethanol nanofluid, more interfacial interaction is resulted that causes higher relative dynamic viscosity while for CuO/water lower interfacial interaction between nanoparticles surface and water molecules are resulted which leads to the lower values for this parameter. The results of this study implied that with increase the temperature from 25 to 70 °C at the condition where nanoparticles mass fraction was chosen to be 5 wt%, the value of dynamic viscosity of CuO/ethanol, CuO/deionized water, CuO/ethylene glycol declined 69%, 66%, and 65% respectively. Finally, a correlation was proposed for the relative dynamic viscosity of nanofluid based on the CuO nanoparticles mass fraction and temperature of the basefluid and nanoparticles.

A series of nanocomposites adsorbents with different magnetite/carbon black ratios were synthesized by using the co-precipitation method and used for separation of LREEs (Ce, La, and Nd) from aqueous solution. The adsorption efficiency of nanocomposites is strongly dependent on both pH and the loading carbon on nanocomposite. The maximum adsorption capacity (370 mg/g) was reported by nanocomposite with 20% Fe3O4 and 80% carbon in pH 7 for LREE initial concentration of 250 ppm. Results revealed that the LREEs adsorption behavior of the optimal adsorbent fits well with Langmuir isotherm and pseudo-first-order kinetic model. Moreover, the average values of thermodynamic parameters suggest the endothermic and irreversible chemisorption mechanism. An empirical correlation was obtained by using GMDH (Group Method of Data Handling)-based Neural Network to predict the adsorption kinetics of LREEs as a function of ion's electronegativity, molecular weight, and initial concentration. The results showed that the correlation can predict the experimental data mostly lower than 12.5% and it can predict the results of other researches with similar conditions with up to 25% from the experimental values. Finally, the results of sensitivity analysis revealed that the adsorption of LREEs is more sensitive to ions electronegativity and molecular weight at equilibrium conditions.

In this study, a fixed-bed catalytic membrane reactor was used for the production of ethylene and cyclohexane from ethane and benzene. A two-dimensional non-isothermal mathematical model was used for estimating the performance of the membrane reactor. Furthermore, the effect of inlet temperature (720–1080 K), feed molar ratio (3–10) and the reactor spacetime (1–76 kgCat.s/mol) was studied on the conversion of ethane to ethylene and benzene to cyclohexane. The results of modeling showed that with the increase of inlet temperature the conversion of both (de)-hydrogenation reactions increased and the 95% of ethane conversion was achieved when the molar ratio of benzene/ethane was fixed on 3. The hydrogenation of benzene at the shell side of the catalytic membrane reactor enhanced the production of ethylene due to the exothermic nature of the hydrogenation reaction, resulting in heat conduction through the membrane and glass substrate into the tube side. The comparison between experimental data reported in literature and modeling showed that the deviation of data obtained by mathematical modeling from experimental values ranged from 15.2 to 19.8% at various spacetimes. In addition, the results of sensitivity analysis showed that the conversion of benzene and ethane is more sensitive to the inlet temperature (up to 160% change on conversion) in comparison to the other parameters including feed ratio and the reactor spacetime. Moreover, at a temperature above 1128 K, the overall performance of the catalytic membrane reactor increased significantly.

Using nanofluids as absorbent is a novel technique for the enhancement of mass transfer in gas absorption process. In this article, a bubble column absorption system was used to investigate the effects of nanoparticle size on carbon dioxide (CO2) absorption in silica/water nanofluid. In the experimental setup, CO2 was injected as frequent bubbles from the bottom of the column containing silica/water nanofluid with different particle sizes of 10.6, 20, 38.6, and 62 nm. The rate of carbon dioxide absorption in silica-water nanofluid increased with nanoparticle size and maximum absorption rate or molar flux was obtained at 0.01 wt% of nanoparticles for all nanofluids with different nanoparticles sizes. Mass transfer parameters including diffusion coefficient, renewal surface rate and thickness of diffusion layer within liquid was also investigated at different nanoparticle sizes. The results show that by increment of nanoparticle size, the renewal surface rate increased while diffusivity and liquid-film thickness decreased. Consequently, Mass transfer coefficients increased by increment of nanoparticle size. Finally a new correlation was proposed incorporating nanoparticle diameter for estimating mass transfer coefficient.

In this study the effects of CuO nanoparticles mass fraction and temperature was studied on the dynamic viscosity and thermal conductivity of CuO/viscous paraffin nanofluid. TEM and DLS analysis as well as zeta potential test were performed for obtaining the morphology and nanoparticles stability within the basefluid. The results of TEM and DLS images exhibited that the average CuO nanoparticles diameter was ranged from 15 to 30 nm. Moreover, Zeta potential analysis showed high stability of nanoparticles in the basefluid. In addition, the results showed that with the increment of nanoparticles mass fraction and temperature the ratio of the thermal conductivity of nanofluid to basefluid increased and this parameter increases significantly with the temperature at the temperature below 40 and 70 °C where the mass fraction was chosen below and higher than 2.5 wt%, respectively. Also the results showed that with the increase of temperature the ratio of dynamic viscosity of nanofluid to basefluid decreases insignificantly and with the increment of nanoparticle load this parameter enhances tangibly. Moreover, two separated correlation including temperature and mass fraction of CuO nanoparticle was estimated by using hybrid GMDH-type neural network method for estimating relative dynamic viscosity and thermal conductivity of nanofluid. The results declared that the deviation of the data obtained by correlation from the experimental values was mostly

In this study, treated eggplant peel was used as an adsorbent to remove Pb2+ from aqueous solution. For this purpose batch adsorption experiments were performed for investigating the effect of contact time, pH, adsorbent dose, solute concentrations, and temperature. In order to assess adsorbent’s physical and chemical properties, Fourier transform infrared spectroscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy were used. The results showed that the adsorption parameters for reaching maximum removal were found to be contact time of 110 min, adsorbent dose of 0.01 g/ml, initial lead(II) concentration of 70 ppm, pH of 4, and temperature of 25°C. Moreover, for the experiments carried out at pH > 4 the removal occurred by means of significant precipitation as well as adsorption. Furthermore, these results indicated that the adsorption followed pseudo-second-order kinetics model implying that during the adsorption process strong bond between lead(II) and chemical functional groups of adsorbent surface took place. The process was described by Langmuir model (R2 = 0.99; maximum adsorption capacity 88.33 mg/g). Also thermodynamics of adsorption was studied at various temperatures and the thermodynamic parameters including equilibrium constant (K), standard enthalpy change, standard entropy change, and standard free energy changes were obtained from experimental data.

A series of nanocomposites adsorbents with different magnetite/carbon black ratios were synthesized by using the co-precipitation method and used for separation of LREEs (Ce, La, and Nd) from aqueous solution. The adsorption efficiency of nanocomposites is strongly dependent on both pH and the loading carbon on nanocomposite. The maximum adsorption capacity (370 mg/g) was reported by nanocomposite with 20% Fe3O4 and 80% carbon in pH 7 for LREE initial concentration of 250 ppm. Results revealed that the LREEs adsorption behavior of the optimal adsorbent fits well with Langmuir isotherm and pseudo-first-order kinetic model. Moreover, the average values of thermodynamic parameters suggest the endothermic and irreversible chemisorption mechanism. An empirical correlation was obtained by using GMDH (Group Method of Data Handling)-based Neural Network to predict the adsorption kinetics of LREEs as a function of ion’s electronegativity, molecular weight, and initial concentration. The results showed that the correlation can predict the experimental data mostly lower than 12.5% and it can predict the results of other researches with similar conditions with up to 25% from the experimental values. Finally, the results of sensitivity analysis revealed that the adsorption of LREEs is more sensitive to ions electronegativity and molecular weight at equilibrium conditions.

In this study the effects of various oxide nanoparticles on viscosity of crude oil-based nanofluid were investigated. Furthermore, the effects of temperature and mass fraction of TiO2, NiO, Fe2O3, ZnO and WO3 nanoparticles on relative viscosity of nanofluid were studied. The morphology and stability of nanoparticles were characterized by using TEM and DLS analysis. The results of characterization showed that the average nanoparticle diameter ranged from 10 to 40 nm for different oxide nanoparticles. Also the results of experiments showed that with the increment of temperature the ratio of the nanofluid viscosity to basefluid declined. Moreover, for nanofluid containing nanoparticles with higher density the relative viscosity increases significantly and with the temperature enhancement higher than 50 °C the values of relative viscosities are less than unity declaring a lower viscosity of nanofluids with respect to basefluid. Finally, an empirical correlation comprising nanoparticle density, temperature, and mass fraction was obtained based on regression analysis for estimation of relative viscosity of nanofluid. The results exhibited that the deviation of the correlation from the experimental values was mostly less than 20% and the results of other researchers agree well with the data predicted by the correlation of this study.

In this study, the enhancement of physical absorption of carbon dioxide by Fe3O4-water nanofluid under the influence of AC and DC magnetic fields was investigated. Furthermore, a gas-liquid mass transfer model for single bubble systems was applied to predict mass transfer parameters. The coated Fe3O4 nanoparticles were prepared using co-percipitation method. The results from characterization indicated that the nanoparticles surfaces were covered with hydroxyl groups and nanoparticles diameter were 10–13 nm. The findings showed that the mass transfer rate and solubility of carbon dioxide in magnetic nanofluid increased with an increase in the magnetic field strength. Results indicated that the enhancement of carbon dioxide solubility and average molar flux gas into liquid phase, particularly in the case of AC magnetic field. Moreover, results demonstrated that mass diffusivity of CO2 in nanofluid and renewal surface factor increased when the intensity of the field increased and consequently diffusion layer thickness decreased. © 2016 American Institute of Chemical Engineers AIChE J, 63: 2176–2186, 2017

In this study, a new approach consisting of chemical treatment steps followed by electrospinning process was applied to produce cellulose nanofibers from wheat straws. Wheat straws were initially pretreated by NaOH solution to open the complex structure of raw materials and remove non-cellulosic materials. Then, acid and alkali hydrolysis was separately performed to eliminate hemicellulose and soluble lignin. Also, bleaching processes were implemented to remove the insoluble lignin. Cellulose nanofibers were produced by electrospinning of various concentrations of cellulose in different solvents including sodium hydroxide/urea/thiourea, pure trifluoroacetic acid (TFA), and TFA/methylene chloride. Images obtained by Scanning Electron Microscope (SEM) showed long and uniform nanofibers produced from electrospinning of cellulose/TFA/methylene chloride solution. An epoxy based laminated composite was prepared by a lamina of cellulose microfiber and electrospun nanofiber mat using hand lay-up composite manufacturing method. The fracture surface of the epoxy nanocomposite was analyzed by SEM images. In addition, the mechanical properties of laminated epoxy composites were compared with pure epoxy by conducting tensile and impact tests. Tensile test results showed that the ultimate tensile strength, elongation, and modulus of laminated epoxy nanocomposites were significantly increased. Moreover, it was found that by adding a nanofiber lamina in the epoxy composite, the impact resistance was significantly improved as a result of crack growth prevention.

In this paper, comprehensive examinations were performed to investigate the effects of nanoparticles on sweetening of biogas which is produced in North Isfahan Waste Water Treatment Plant (NIWWTP) through novel bioscrubbing (BS) method in pilot scale. In the present study, two various nanofluids: Synthesized Silica-water nanofluid with nanoparticle mass fraction of 0.1%wt. (SS100), and Exfoliated Graphene Oxide-water nanofluid with 0.02%wt. (EGO020) were used to intensification of H2S absorption in the first part of BS process. The results showed that absorption capacity of the SS100 and EGO020 nanofluids is far more than the base fluid (distilled water), so the absorption column performance was enhanced. This work also reveals that the significant influence of the nanoparticles in the performance of second part of the bioscrubber (the bioreactor) and it was found that H2S removal was achieved to 98%, 97% and 86% when the BF, SS100 and EGO020 respectively were used as agent fluids. Due to the fact that the absorption of H2S in SS100 nanofluid is higher compared to pure BF and removal efficiency in the bioreactor for this nanofluid is similar to BF, the aforementioned nanofluid (SS-100) was found to be the best choice for enhancement of bioscrubber performance.