Showing papers in "Journal of The Taiwan Institute of Chemical Engineers in 2014"

Visible light degradation of textile effluent using novel catalyst ZnO/γ-Mn2O3

Abstract: The novel ZnO/γ-Mn2O3 (various weight percentages) nanocomposite catalysts were prepared by thermal decomposition method and their size, shape, and surface area were characterized by various techniques. Further, the prepared samples were used to degrade methylene blue (MB) and methyl orange (MO) in aqueous medium under visible light irradiation. Finally, the best catalyst was employed to degrade phenol and a textile effluent. The recycling ability and their efficiency of catalyst are discussed in detail.

Numerical study of MHD boundary layer flow of a Maxwell fluid past a stretching sheet in the presence of nanoparticles

Abstract: In the present article, two dimensional boundary-layer flows and the heat transfer of a Maxwell fluid past a stretching sheet are studied numerically The effects of magnetohydrodynamics (MHD) and elasticity on the flow are considered Moreover, the effects of nanoparticles are also investigated Similarity transformations are presented to convert the governing nonlinear partial differential equation into coupled ordinary differential equations The reduced boundary layer equations of the Maxwell nanofluid model are solved numerically The effects of the emerging parameters, namely, the magnetic parameter M, the elastic parameter K, the Prandtl parameter Pr, the Brownian motion Nb, the thermophoresis parameter Nt and the Lewis number Le on the temperature and the concentration profile are discussed Interesting results are shown graphically The skin friction coefficient, the dimensionless heat transfer rate and the concentration rate are also plotted against the flow control parameters

Natural convection heat transfer in a cavity with sinusoidal wall filled with CuO–water nanofluid in presence of magnetic field

Abstract: Control volume based finite element method (CVFEM) is applied to investigate flow and heat transfer of CuO–water nanofluid in presence of magnetic field. The enclosure has a sinusoidal wall under constant heat flux. The effective thermal conductivity and viscosity of nanofluid are calculated by KKL (Koo–Kleinstreuer–Li) correlation. In this model effect of Brownian motion on the effective thermal conductivity is considered. The numerical investigations are conducted at a fixed Prandtl number equal to 6.2. Various values of non-dimensional governing parameters such as volume fraction of nanoparticles (ϕ), Rayleigh number (Ra), dimensionless amplitude of the sinusoidal wall (a) and Hartmann number (Ha) are examined. Also a correlation of Nusselt number corresponding to active parameters is presented. The results show that Nusselt number is an increasing function of nanoparticles volume fraction, dimensionless amplitude of the sinusoidal wall and Rayleigh number while it is a decreasing function of Hartmann number.

Batch and fixed bed column studies for the removal of Indosol Yellow BG dye by peanut husk

Abstract: Biosorption is an emerging technique for water treatment utilizing abundantly available biomaterials. The biosorption potential of peanut husk biomass was investigated in batch and continuous mode study. Batch experiments were conducted to compare the biosorption capacity of native, acetic acid treated and immobilized peanut husk biomass. Different important process parameters like pH, contact time, biosorbent dose, initial dye concentration and temperature were optimized during batch experiments. Maximum removal of Indosol Yellow BG dye was observed at pH 2 with 0.05 g/50 mL biosorbent dose. The biosorption process was found to be exothermic in nature. Maximum dye removal (79.7 mg/g) was obtained with acetic acid treated peanut husk biomass. Different kinetic and equilibrium models were applied to the experimental data. Pseudo-second-order kinetic model and Langmuir adsorption isotherm model showed better fitness to the experimental data. Thermodynamic study was also carried out to check out the feasibility of biosorption process. Fixed bed study was carried out to optimize bed height, flow rate and initial dye concentration. Maximum dye removal in continuous mode experiments was found to be 25.9 mg/g. Thomas model and Bed Depth Service Time (BDST) models were applied to the continuous mode experimental data. Characterization of biosorbent was carried out by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). FT-IR analysis showed the involvement of hydroxyl, carbonyl and carboxyl groups in the biosorption process. These findings revealed that peanut husk biomass has a high biosorption potential and it can be used for the treatment of dye containing waste water.

Design and evaluation of chitosan/hydroxyapatite composite nanofiber membrane for the removal of heavy metal ions from aqueous solution

Abstract: The performance of chitosan/hydroxyapatite (Cs/HAp) composite nanofiber membrane prepared by electrospinning process for the removal of lead, cobalt and nickel ions from aqueous solution was investigated. The prepared nanofiber membranes were characterized by FTIR, SEM and BET analysis. A response surface methodology based on Box–Behnken Design (BBD) was used to predict the average diameter of electrospun nanofibers. In optimum conditions (voltage of 18.90 kV, tip-collector distance of 15.60 cm and flow rate of 0.43 ml/h), the minimum experimental fiber diameter was obtained 198 nm which was in good agreement with the predicted value by the BBD analysis (200.6 nm). Then, the adsorption experiments were carried out to investigate the effect of different adsorption parameters, such as contact time, initial concentration and temperature in a batch system. The kinetic and equilibrium data were well described by pseudo-second-order and Langmuir models, respectively. Thermodynamic parameters were evaluated to obtain the nature of adsorption process onto the Cs/HAp composite nanofibers. The obtained results of reusability of nanofiber membrane after five sorption–desorption cycles offer promising potential in industrial activities.

Magnetic field effect on nanofluid flow and heat transfer using KKL model

Abstract: In this paper, MHD effect on natural convection heat transfer in an inclined L-shape enclosure filled with nanofluid is studied. The numerical investigation is carried out using the control volume based finite element method (CVFEM). The fluid in the enclosure is a water-based nanofluid containing Al2O3 nanoparticle. The effective thermal conductivity and viscosity of nanofluid are calculated by KKL (Koo–Kleinstreuer–Li) correlation in which effect of Brownian motion on the effective thermal conductivity is considered. The heat transfer between cold and hot regions of the enclosure cannot be well understood by using isotherm patterns so heatline visualization technique is used to find the direction and intensity of heat transfer in a domain. Effect of Hartmann number, volume fraction of nanoparticle, Rayleigh number and inclination angle on streamline, isotherm and heatline are examined. The results show that Nusselt number increases with increase of Rayleigh number and volume fraction of nanoparticle while it decreases with augment of Hartmann number and inclination angle. Enhancement in heat transfer has reverse relationship with Hartmann number and Rayleigh number.

Fluoroquinolones antibiotics adsorption onto microporous activated carbon from lignocellulosic biomass by microwave pyrolysis

Abstract: Microwave-assisted KOH activation has been adopted to prepare activated carbon from a lignocellulosic biomass, Albizia lebbeck seed pods. Fluoroquinolones antibiotics such as ciprofloxacin (CIP) and norfloxacin (NOR) were removed from aqueous solutions by adsorption on prepared carbon. The surface area, micropores volume, and mesopores volume of such carbon were 1824.88 m2/g, 0.645 cm3/g and 0.137 cm3/g, respectively. The effects of pH, adsorbent dose, and contact time on the adsorptive removal process were studied. Maximum removal percentages of 96.12% and 98.13% were achieved for CIP and NOR adsorption, respectively. The best fitting for equilibrium adsorption data of both antibiotics was obtained by the Langmuir isotherm with maximum capacities of 131.14 and 166.99 mg/g for CIP and NOR, respectively. The kinetic data were found to follow closely the pseudo-second order model for both antibiotics. Results of thermodynamic studies showed an endothermic CIP adsorption compared to an exothermic NOR adsorption under examined conditions.

Adsorptive removal of CO2 on highly microporous activated carbons prepared from Eucalyptus camaldulensis wood: Effect of chemical activation

Abstract: A series of activated carbons (ACs) were prepared from Eucalyptus camaldulensis wood by chemical activation with H3PO4, ZnCl2 at different impregnation ratios as well as by pyrolysis, followed by activation with KOH. The porosity characteristics of these ACs were determined by N2 adsorption isotherms. Through varying the H3PO4/biomass ratio from 1.5 to 2.5, the prepared ACs displayed BET surface areas in the range of 1875–2117 m2/g with micropores content of 69–97%. For the ZnCl2 activated series, BET surface areas varying from 1274.8 to 2107.9 m2/g with micropores content of 93–100% were obtained from impregnation ratios of 0.75–2.0. The AC obtained by KOH had the largest BET surface area of 2594 m2/g and the high micropore content of 98%. In addition, the FTIR and SEM analyses conducted for characterizing the ACs and the CO2 adsorption onto all series of the eucalyptus wood based ACs at pressures ranging from 0 to 16 bar using a volumetric method were investigated. Also the effect of temperature (15–75 °C) on the amount of CO2 adsorbed by the ACs that was prepared with H3PO4, KOH and ZnCl2 was studied. The CO2 adsorption capacity on the AC prepared with KOH was up to 4.10 mmol/g at 1 bar and 303 K, having an increase of about 63% in comparison with the commercial AC.

MHD free convection in an eccentric semi-annulus filled with nanofluid

Abstract: In this study magnetohydrodynamic effect on free convection of nanofluid in an eccentric semi-annulus filled is considered. The effective thermal conductivity and viscosity of nanofluid are calculated by the Maxwell–Garnetts (MG) and Brinkman models, respectively. Lattice Boltzmann method is applied to simulate this problem. This investigation compared with other works and found to be in excellent agreement. Effects of the Hartmann number, nanoparticle volume fraction, Rayleigh numbers and position of the inner circular cylinder on flow and heat transfer characteristics are examined. Also a correlation of Nusselt number corresponding to active parameters is presented. The results show that Nusselt number has direct relationship with nanoparticle volume fraction and Rayleigh number but it has inverse relationship with Hartmann number and position of inner cylinder at high Rayleigh number. Also it can be concluded that heat transfer enhancement increases with increase of Hartmann number and decreases with augment of Raleigh number.

An investigation into the adsorption removal of ammonium by salt activated Chinese (Hulaodu) natural zeolite: Kinetics, isotherms, and thermodynamics

Abstract: The development of the process of sodium activation of zeolite has been an effective technique for enhancing the efficiency of ammonium removal. In this research, the optimum conditions for the activation of Chinese (Hulaodu) zeolite of the most effective parameters such as sodium concentration, stirring time, and temperature were determined. The most efficient conditions were selected according to the highest ammonium removal capacity. The characteristics of activated zeolite (ActZ) and its mechanism of ammonium removal were investigated and compared with that of natural zeolite (NZ). Additionally, both zeolites were analyzed by scanning electron microscopy (SEM), Zeta potential, X-ray diffraction (XRD), thermogravimetry (TG) and BET surface analysis. The activated zeolite revealed the highest ammonium removal efficiency reaching up to 98% based on stirring time, zeolite loading, initial ammonium concentration, temperature and pH. The adsorption kinetic was explored and fitted best with the pseudo-second-order model, whereas adsorption isotherm results illustrated that Langmuir model (LM) provided the best fit for the equilibrium data. Moreover, thermodynamic parameters such as change in free energy (Δ G °), enthalpy (Δ H °) and entropy (Δ S °) were also calculated. The parameters revealed that the exchange of ammonium ion by activated zeolite occurred spontaneously at ambient conditions (25 °C). It was concluded that when Chinese (Hulaodu) zeolite is activated under the condition of 1 M NaCl, 70 °C and stirring time of 30 min, an excellent removal of NH 4 + was obtained.

Adsorption and thermodynamic study of Cephalosporins antibiotics from aqueous solution onto MgO nanoparticles

Abstract: The adsorption characteristics of Cephalosporins antibiotics from aqueous solution were investigated using magnesium oxide (MgO) nanoparticles. Liquid phase adsorption experiments were conducted. Batch adsorption studies are carried out by observing the effect of experimental parameters, namely amount of adsorbents, pH, temperature and contact time. The drug removal data were fitted on Langmuir adsorption equations. The pseudo second-order kinetic model was indicated with the activation energy of 7.6682 and 5.3745 kJ/mol for Cephalexin and Cefixime, respectively. The values of the enthalpy (ΔH#) and entropy of activation (ΔS#) were 5.0851 kJ/mol and −286.67 J/mol K for Cephalexin; 3.1952 kJ/mol and −303.70 J/mol K for Cefixime, respectively. The free energy of activation (ΔG#) at 30 °C was 97.9 kJ/mol. Thermodynamic analysis showed negative values of ΔG° indicating adsorption was favourable and spontaneous, negative values of ΔH° indicating exothermic physical adsorption of Cephalosporins using MgO nanoparticles.

Adsorption of Congo red from aqueous solutions using cationic surfactant modified wheat straw in batch mode: Kinetic and equilibrium study

Abstract: An agricultural by-product, wheat straw, was treated using cetyltrimethyl ammonium bromide (CTAB) to improve adsorption capacity for the removal of Congo red dye (CR, anionic dye) from aqueous solutions in batch mode. The effect of contact time, CR concentration and temperature on adsorption was presented. The results showed that it was in favor of adsorption at pH 4–5 and lower temperature. Adsorption capacity of MWS for CR is 665 mg/g at 303 K. Three kinetic models, pseudo-first-order kinetic model, pseudo-second-order kinetic model and Elovich model, were selected to fit the kinetic data and pseudo-first-order kinetic model was best. Three adsorption isotherm models, Langmuir, Freundlich and Temkin, were used to fit the experimental data and Langmuir model was better available. The process was exothermic and spontaneous according to thermodynamic parameters. It was concluded that MWS be promising to adsorb anionic dye from solution.

Nonlinear radiative heat transfer in the flow of nanofluid due to solar energy: A numerical study

Abstract: Radiation effects in the two-dimensional stagnation-point flow of viscous nanofluid due to solar energy are investigated. Heat transfer subject to thermal radiation, Joule heating, viscous dissipation and convective boundary conditions is considered. A different application of Rosseland approximation for thermal radiation is introduced in this study. The governing equations are simplified through the boundary layer assumptions and then transformed into non-dimensional forms by appropriate transformations. The resulting differential systems are solved numerically through fourth-fifth order Runge–Kutta method (RK45) using a shooting technique. The influences of different parameters are explained through graphs for velocity, temperature and concentration and numerical values of local Nusselt and Sherwood numbers. A comparative analysis of the solutions is performed through previous studies in some limiting cases. Both the temperature and wall temperature gradient are increasing functions of the radiation parameter. The excessive movement of nanoparticles in the base fluids results in the deeper absorption of solar radiations in the liquids.

Synthesis of BiOBr, Bi3O4Br, and Bi12O17Br2 by controlled hydrothermal method and their photocatalytic properties

Abstract: Bismuth oxybromides have received remarkable attention in recent years because of their stability, suitable band gaps, and relatively superior photocatalytic abilities. In the preparation procedure, BiBr 3 is dissolved in an aqueous solution, NaOH aqueous solution is added to adjust the pH value, and then the aqueous solution is transferred into a 30 mL Teflon-lined autoclave, which is heated to 100–250 °C for 4, 6, and 12 h and then naturally cooled to room temperature. The composition and morphologies of bismuth oxybromides could be controlled by adjusting some growth parameters, including reaction pH, time, and temperature. The products are characterized by XRD, SEM-EDS, HR-TEM, DR-UV, BET, and HR-XPS. It is demonstrated that BiOBr, Bi 3 O 4 Br, and Bi 12 O 17 Br 2 can be selectively prepared through a facile solution-based hydrothermal method. UV–vis spectra show the three materials being the indirect semiconductors with optical bandgaps of 2.85, 2.66, and 2.42 eV. Photocatalytic efficiency of the powder suspension is evaluated by measuring the crystal violet (CV) or salicylic acid (SA) concentration. This is a study to show the superior activities of BiOBr, Bi 3 O 4 Br, and Bi 12 O 17 Br 2 as a promising visible-light-responsive photocatalyst.

Silica nanopowders/alginate composite for adsorption of lead (II) ions in aqueous solutions

Abstract: The aim of the present work was to study the Pb(II) ions adsorption by entrapped silica nanopowders within calcium alginate to determine the isotherm, kinetic and thermodynamic of the adsorption process. According to the results, an optimal initial pH of 5.0 was found for the Pb(II) adsorption. The adsorbed Pb(II) ions reached to 36.51 mg/g as the contact time increased to 180 min at an initial Pb(II) concentration of 50 mg/L. However, a contact time of 90 min was selected as equilibrium time because of no significant increase in Pb(II) adsorption after this time. The results of isotherm and kinetic studies showed the Langmuir isotherm and pseudo-second order kinetic model were the best fitted models ( R 2 > 0.999). The maximum adsorption capacity for Pb(II) adsorption onto entrapped silica nanopowders was estimated to be 83.33 mg/g. According to the Dubinin–Radushkevich (D–R) isotherm model, Pb(II) adsorption onto the composite follows a chemical mechanism ( E = 10 kJ/mol). Negative Δ G ° and Δ H ° values indicated spontaneous and exothermic nature of the Pb(II) adsorption onto entrapped silica nanopowders, respectively. In addition, the results of continuous flow mode study exhibited that increasing empty-bed contact time (EBCT) from 5 to 20 min resulted in increasing the specific throughput (St) from 8.42 to 11.22 mL/g, respectively.

Hydrothermal synthesis of SrTiO3 nanocubes: Characterization, photocatalytic activities, and degradation pathway

Abstract: The strontium titanate, SrTiO3, nanocubes are synthesized by the autoclave hydrothermal method under the alkaline condition with TiO2 and Sr(OH)2·8H2O as the starting materials at various reaction temperatures, various NaOH concentration and reaction duration time. The FE-SEM results indicate that the reaction temperature has strong influence on the granular size of SrTiO3 (STO). The EDS results for STO giving the Sr/Ti atomic ratio of ca. 1 for all prepared compounds confirmed the formation of STO and were comparable to the HR-XPS results. The photo-degradation efficiency of the crystal violet (CV) dye by STO is performed under the UV light irradiation, various pH reaction media conditions and the dark room condition for comparisons. STO shows the optimal photo-degradation efficiency when the catalyst is prepared at 130 °C. The degradation intermediates are separated and identified by the HPLC-ESI-PDA-MS in order to propose the possible photo-degradation pathways based on the concentration ratio variations of intermediates during the reaction course of time. The N-demethylation reaction occurs to give a consecutive series of intermediates with triphenylmethane (TMP) chromophore (588.3–541.0 nm), accompanied by the oxidative reaction occurring at the central carbon of CV which gives another series of intermediates with diaryl-ketone chromophore (377.2–339.1 nm) and 4-aminophenol (308.9–278.1 nm). The peaks of concentration ratio for the consecutive formation intermediates along the time course further confirm the proposed pathways.

Numerical study of MHD two-phase Couette flow analysis for fluid-particle suspension between moving parallel plates

Abstract: In this study, steady and unsteady magneto-hydrodynamic (MHD) Couette flows between two parallel infinite plates have been studied through numerical Differential Quadrature Method (DQM) and analytical Differential Transformation Method (DTM), respectively. Coupled equations by taking the viscosity effect of the two phases for fixed and moving plates have been introduced. The precious contribution of the present study is introducing new, fast and efficient numerical and analytical methods in a two-phase MHD Couette fluid flow. Results are compared with those previously obtained by using Finite Difference Method (FDM). The velocity profiles of two phases are presented and a parametric study of physical parameters involved in the problem is conducted. As an outcome, when magnetic source is fixed relative to the moving plate, by increasing the Hartmann number, velocity profiles for both phases increased, but when it is fixed relative to the fluid an inverse treatment is observed.

Dendrimer functionalized nanoarchitecture: Synthesis and binary system dye removal

Abstract: In this paper, dendrimer functionalized titania nanoarchitecture (DFTN) was synthesized and characterized. The ability of DFTN to remove dyes from single and binary systems was studied. Fourier transform infrared (FTIR) and scanning electron microscopy (SEM) were used to characterize DFTN. Direct red 23 (DR23), direct green 6 (DG6), and direct red 31 (DR31) were used as anionic dyes. The effect of adsorbent dosage, pH, dye concentration, and salt on dye removal was evaluated. Kinetic, isotherm, and thermodynamic of dye removal were evaluated. The capacity of DFTN to remove DR23, DG6, and DR31 was 244, 189, and 243 mg/g, respectively. Dye removal kinetics and isotherm using DFTN fitted with the pseudo-first order kinetics and Langmuir, respectively. The thermodynamic data indicated the dye adsorption onto adsorbent is spontaneous, endothermic, and physical adsorption.

Development of nano-hydroxyapatite/chitosan composite for cadmium ions removal in wastewater treatment

Abstract: Hydroxyapatite nanorods (nHAp) and nano-hydroxyapatite chitosan composites (nHApCs) were proposed for the removal of Cd2+ ions in water treatment. The high resolution transmission electron microscopy, energy dispersive X-ray analysis, X-ray diffraction spectrophotometer, Fourier transform infrared spectrophotometer and Zeta potential measurements were all employed to reveal the morphology, composition, crystal structure, functionality and stability of the prepared sorbents (nHAp and nHApCs). The potential of these synthesized sorbents to remove Cd2+ ions from aqueous solutions was investigated in batch experiments, where several parameters such as the sorbate/sorbent's contact time, initial Cd2+ ions concentration, pH and sorbent dosage were investigated. The equilibrium concentration of Cd2+ ions was identified by the atomic absorption spectrophotometry. The Cd2+ uptake was quantitatively evaluated using the Pseudo second order kinetic equation, Freundlich and Langmuir models. It is remarkable that with these sorbents (nHAp, nHApCs), up to 92% of Cd2+ could be removed “100 ppm initial cadmium concentration in 200 mL, 0.4 g nHAp and pH = 5.6″. The sorption capacity of nHAp and nHApCs to Cd2+ was 92 and 122 mg/g respectively, which appears excellent when compared to other previously reported materials. This capacity could be enhanced by increasing initial Cd2+ concentration and the nHAp/Cd2+ mass ratio. Furthermore, the sorbents’ regeneration was addressed and found promising.

MHD mixed convection of nanofluid filled partially heated triangular enclosure with a rotating adiabatic cylinder

Abstract: MHD mixed convection of Cu–water nanofluid filled triangular enclosure with a rotating cylinder is investigated numerically. A partial heater is added on the left vertical wall of the cavity and the right inclined wall is kept at constant temperature. Other walls of the triangular cavity and cylinder surface are assumed to be adiabatic. The governing equations are solved using the finite element method. The effects of the Grashof number, Hartmann number, angular rotational speed of the cylinder and volume fraction of the nanoparticle on fluid flow and heat transfer are investigated numerically. The second law of thermodynamics is also applied to the flow and heat transfer corresponding to different combinations of parameters. It is observed that with increasing the Hartmann number the total entropy generation, local and averaged heat transfer decrease. Averaged Nusselt number increases with the Grashof number. Averaged heat transfer and total entropy generation increase with increase in the angular rotational speed of the cylinder. 50.4% and 37.4% of heat transfer enhancements are obtained for ω = 20 and ω = −20 compared to motionless cylinder ω = 0. Heat transfer and total entropy generation increase as the solid volume fraction of nanoparticle increases.

Calcined eggshells as a new biosorbent to remove basic dye from aqueous solutions: Thermodynamics, kinetics, isotherms and error analysis

Abstract: The biosorption of basic yellow 28 dye onto calcined eggshells as a new and potential biosorbent have been studied. Batch biosorption studies were conducted to evaluate the effect of various parameters such as contact time, temperature, initial dye concentration, biosorbent dose and ionic strength on the removal of BY 28. From thermodynamic studies, it was seen that the biosorption was spontaneous and exothermic. Biosorption kinetics data were tested using pseudo-first-order and pseudo-second-order models. Kinetic studies showed that the biosorption followed a pseudo-second-order reaction. Maximum of biosorption capacity was attained 28.87 mg/g. Thermodynamic studies reveals that the biosorption of dye was occurred as exothermic in nature (ΔH = −4.3185 kJ/mol), spontaneous and reflects the decreased randomness at the solid/solution interface during the biosorption (ΔS = −0.135 j/mol K). The experimental isotherm data were analyzed using the Freundlich, Tempkin, Toth, Dubinin-Radushkevich, Sips or Koble-Corrigan and Generalized isotherms equations using regression analysis linear and non-linear, showed that the Freundlich isotherm best-fits the equilibrium data for adsorptive removal of basic yellow 28 by calcined eggshells. A detailed error analysis has been undertaken to investigate the effect of using different error criteria for the determination of the isotherm parameters which describe the biosorption process.

Potential of waste pumice and surface modified pumice for hexavalent chromium removal: Characterization, equilibrium, thermodynamic and kinetic study

Abstract: The sorption potential of natural (NP) and surface modified pumice using MgCl2 (MGMP) as an abundant and low cost geo-material for the removal of Cr(VI) ion was investigated. The influence of contact time, solution pH, initial metal concentration, amount of absorbents and solution temperature was studied. Natural and modified adsorbents were characterized by means of XRD, XRF, SEM and FTIR technologies. Maximum sorption was observed at pH 1 and 100 mg/L metal concentration. Equilibrium data were accurately fitted onto Langmuir, Freundlich and Temkin isotherms, showing the heterogeneous nature of the adsorbents; maximum sorption capacity according to the Langmuir isotherm were 87.72 mg/g and 105.43 mg/g for NP and MGMP, respectively, showing a high sorption potential if compared to adsorbents used for Cr(VI) removal. Intra-particle model demonstrated that film diffusion was the rate-limiting step instead of intra-particle diffusion, as confirmed from the analysis of pseudo-second order rate constants, showing an absence of limitation due to pore diffusion. Relevance of pumice was confirmed since high regeneration yields were obtained, 94.3% in acidic conditions (1 M HCl) for spent non-modified pumice and 91.3% in alkaline conditions (4 M NaOH) for spent modified pumice.

Thermophoresis particle deposition in mixed convection three-dimensional radiative flow of an Oldroyd-B fluid

Abstract: This article describes heat and mass transfer characteristics in three-dimensional flow of an Oldroyd-B fluid. The flow caused is due to bidirectional stretching surface. Radiation effects are taken into account via Rosseland approximation. In addition the thermophoresis effects are considered. Results of velocities, temperature and concentration are constructed. The obtained results are plotted and discussed for interesting physical parameters. We have seen that the increasing values of thermophoretic parameter leads to a decrease in the concentration field and concentration boundary layer thickness. Also it is noticed that the concentration field corresponding to thermophoretic parameter decays quickly in comparison to concentration field for Schmidt number.

Adsorption and cosorption of ciprofloxacin and Ni(II) on activated carbon-mechanism study

Abstract: Antibiotics and heavy metals often coexist in water bodies due to influxes of various pollution sources. The objective of this study was to evaluate the interaction between Ni(II) and ciprofloxacin (CIP) concerning their adsorption and cosorption onto activated carbon as a function of time, solution pH and initial concentration. Adsorption of Ni(II) and CIP on activated carbon was strongly dependent on solution pH, indicating an electrostatic attraction mechanism. Cosorption of Ni(II) and CIP also strongly depended on solution pH. The presence of CIP suppressed Ni(II) adsorption, especially at low pH, due to the competition of CIP with Ni(II) for adsorption sites. The presence of Ni(II) in the aqueous solution increased the adsorption of CIP onto activated carbon at pH between 3.4 and 6.5, because the positively charged complexes of Ni–CIP with greater sorption affinity to activated carbon than CIP itself form in this pH range.

Catalytic reduction of methylene blue using biogenic gold nanoparticles from Sesbania grandiflora L

Abstract: In the present investigation, we report the synthesis of gold nanoparticles (AuNPs) using leaf extract of Sesbania grandiflora . The processes of nucleation and growth of AuNPs were followed by monitoring the absorption spectra during the reaction. UV–vis spectrum of the aqueous medium containing AuNPs showed a peak at around 534 nm. FE-SEM and TEM micrograph analysis of the AuNPs indicated that they were predominantly spherical, well-dispersed within 7–34 nm. The synthesized AuNPs are observed to have an excellent catalytic activity on the reduction of methylene blue by S. grandiflora extract which is confirmed by the decrease in absorbance maximum values of methylene blue (MB) with respect to time using UV–vis spectrophotometer and is attributed as an effective catalyst for degrading chemical dyes.

Influence of soybean biodiesel content on basic properties of biodiesel-diesel blends

Abstract: The basic properties of the soybean biodiesel-diesel blends were measured according to the corresponding standards, and the influence of biodiesel content on the blends properties was evaluated. The results indicated that, with the increase of the biodiesel content in the blends, the difference between the final and the initial boiling point (IBP) was reduced, the acid number increased, the sulfur content and the cetane index decreased. The cloud point and cold filter plugging point (CFPP) were similar to that of diesel with the volume fraction of biodiesel up to 30%. The peroxide value was slightly increased with the time when the volume fraction of biodiesel was less than 20%, but was increased dramatically when more than 20%. Kay's mixing rule was used for predicting the properties and the low calculated absolute average deviations (AAD) demonstrated that the predicted properties were in better agreement well with the measured values.

Evaluation of thermal, thermal-alkaline, alkaline and electrochemical pretreatments on sludge to enhance anaerobic biogas production

Abstract: Anaerobic digestion was regarded as one of the ways to recover energy from waste activated sludge in this study. After applying thermal-, thermal-alkaline-, electrochemical- and alkaline-pretreatments to waste activated sludge to promote the digestion efficiency, biogas yield and volatile solid (VS) removal were investigated to evaluate the effectiveness of the pretreatments for the purpose. The highest biogas production (647 L/kg VS) was achieved after pretreatment by electrochemical method. The highest daily biogas production rate was obtained through alkaline pretreatment. Biogas production has no positive relationship with the solubilization degree of sludge. The highest VS removal rate could be got by the pretreatment of thermo-alkaline and electrochemical methods, and the sludge achieved the stabilization after the shortest digestion time with the treatment of electrochemical.

Adsorption of anthraquinone dye onto eco-friendly semi-IPN biocomposite hydrogel: Equilibrium isotherms, kinetic studies and optimization

Abstract: This work demonstrates the use of a new eco-friendly semi-IPN cellulose- graft -polyacrylamide/hydroxyapatite biocomposite hydrogel (EBH), for efficient dye removal from aqueous solution. Here, novel eco-friendly biocomposite hydrogels were prepared from grafted cellulose and hydroxyapatite, and the resulting biocomposites were well characterized. Adsorption characteristics of the as-prepared composite hydrogel were tested by using anthraquinone dye, reactive blue 2 (RB2) as an adsorbate. The sorption kinetics, isotherms, and thermodynamics of RB2 onto the composite hydrogel have been assessed at various operation conditions such as composite dosage, solution pH, temperature, contact time and initial dye concentration. The equilibrium data followed both Redlich–Peterson and Langmuir models. It was found that RB2 adsorption process followed the pseudo-second-order kinetics, as well as the Elovich model. The thermodynamic data indicated that RB2 adsorption onto the composite hydrogel was endothermic and spontaneous. Box–Behnken design was employed to ensure high efficiency and also to optimize the adsorption parameters of RB2 onto EBH. On the basis of the obtained data, we conclude that the composite hydrogel being low-cost and eco-friendly adsorbent might be a reliable alternative to remove hazardous anthraquinone dyes, pigments and heavy metals from aqueous solutions.

Response surface methodology approach for optimization of the removal of chromium(VI) by NH2-MCM-41

Abstract: A central composite design (CCD) combined with response surface methodology (RSM) was employed for maximizing chromium (Cr(VI)) removal from aqueous solution by using amine-functionalized MCM-41 (NH2-MCM-41) Four independent variables namely initial pH, metal ion concentration, temperature and adsorbent dosage were investigated Analysis of variance (ANOVA) of the quadratic model suggested that the predicted values were in good agreement with experimental data Maximum removal was attained as 9870% at initial pH 35, Cr(VI) concentration of 10 mg/L, temperature 40 °C with an adsorbent dosage of 5 g/L The synthesized adsorbent was characterized by Fourier transform infrared spectra (FTIR), X-ray diffraction (XRD) and Energy Dispersive Spectroscopy (EDS) The kinetics were evaluated by pseudo-first-order and pseudo-second-order models, pseudo-second-order model was found to describe the process better with a higher correlation The adsorption data conformed well to Langmuir and Freundlich isotherms Thermodynamic analysis revealed that the adsorption process was spontaneous and endothermic The results from adsorption–desorption cycles showed that NH2-MCM-41 held good desorption and reusability

Adsorption of a textile dye in aqueous phase using mesoporous activated carbon prepared from Iranian milk vetch

Abstract: A B S T R A C T The aim of the present study was to prepare activated carbon from milk vetch and utilize as-prepared activated carbon for sequestering Acid orange 7 (AO7) as an azo dye from batch flow mode experimental reactors. The result of SEM analysis confirmed porous structure for the activated carbon in which the major portion of the pore diameter size distribution was lower than 100 nm with frequency of 67%. As results, the adsorption of AO7 was decreased from 45.90 to 33.35 mg/g with increasing initial pH from 3 to 11, respectively. Increasing adsorbent dosage from 0.5 to 1.5 g/L resulted in increasing the decolorization efficiency (%) from 59.96 to 89.40%, respectively. The experimental data were best represented by the pseudo-second order kinetic model (R 2 = 0.9865) regarding intraparticle diffusion rate. Among studied isotherm models, the adsorption of AO7 onto activated carbon obeyed Langmuir model (R 2 = 0.9907) with a maximum adsorption capacity of about 99 mg/g. The obtained value for mean free energy (0.25 kJ/mol) indicated that the adsorption of AO7 is physical in nature. Comparatively, asprepared activated carbon derived from milk vetch had more adsorption capacity than that of commercial activated carbon for the adsorption of AO7 at the same operational conditions.