Intraparticle Diffusion Kinetic Models Research Articles

Enhanced removal of vanadium(V) from acidic streams using binary oxide systems of TiO2-ZrO2 and TiO2-ZnO type

It is well known that removal of vanadium ions from the natural environment has become a great challenge in recent years. Due to this fact, the present study concerns the application of binary oxides such as TiO2-ZrO2 (molar ratio 9:1) and TiO2-ZnO (molar ratio 7:3) synthesized by the sol–gel method with calcination at 873 K (TZ1 sample) or by the hydrothermal method at 433 K (TZ2 and T7Zn3 samples), respectively. The fabricated adsorbents were subjected to the detailed physico-chemical analysis including: dispersive properties, morphology, crystalline and textural properties as well as chemical composition. The vanadium(V) ions adsorption on the binary oxides was optimized by the experimental conditions such as pH (2–10), adsorbent dose (0.01–0.1 g), vanadium concentration (10–500 mg/L), agitation time (1 min–24 h) and temperature (293–333 K). The pseudo-first-order (PFO), pseudo-second-order (PSO) and intraparticle diffusion (IPD) kinetic models as well as the Langmuir, Freundlich, Temkin and Dubinin-Raduskievich isotherm models were applied for the description of V(V) adsorption. The adsorption capacities were found to be 129.3 mg/g for TZ1, 170.8 mg/g for TZ2 and to 195.9 mg/g for T7Zn3. The endothermic and spontaneous character of V(V) adsorption on the binary oxides was confirmed by the values of thermodynamic parameters. The best fitting of kinetic experimental data to the pseudo-second-order model was obtained. The maximum desorption yield (%D) was achieved using the 1 mol/L NaOH solution (97.96%-T7Zn3, 75.81%-TZ2, 62.88%-TZ1). Applicability of the inorganic oxides in V(V) and Fe(III) removal from spent catalyst leaching solutions was proved.

Production of chemically and microwave activated hazelnut husk as an adsorbent for dye contaminated wastewaters

Adsorption has traditionally been evaluated as an economical and easily applicable process for treating certain wastewaters, such as ones including dyes and heavy metals. Even though adsorbent materials specifically produced for the purpose of wastewater treatment commercially exist, the production cost may create an economic burden on wastewater treatment processes. Agricultural wastes can be valorized as adsorbents in adsorption processes. The adsorption capacity of these wastes can be improved via pre-treatment methods such as chemical application and microwave irradiation. This study investigated the potential applicability of hazelnut husk as an adsorbent for methylene blue (MB) dye. To this purpose, the husk was activated by sequential chemical or water and microwave applications. Structural analysis on the produced adsorbent was performed by Fourier transform infrared spectrophotometry (FTIR) and field emission scanning electron microscopy (FE-SEM). Isotherm (Langmuir, Freundlich, Temkin and Harkins-Jura isotherms) and kinetic (pseudo-first-order, pseudo-second-order, Elovich and intraparticle diffusion kinetic models) behaviours of adsorption were also evaluated. The results indicated that MB could be removed by 92-94% considering all adsorbents produced. Further isotherm and kinetic studies revealed that MB adsorption was both physically and chemically induced, and the reaction followed the pseudo-second-order kinetic model (R2>0.99).

Biogenic magnetic nano hydroxyapatite: Sustainable adsorbent for the removal of perchlorate from water at near-neutral pH

The present work focuses on the utilization of biowaste material for a sustainable environment. In order to support the concept of ‘value-added product from waste’, Eggshell waste, which is a rich source of calcium is considered as a sustainable and renewable precursor for the synthesis of porous hydroxyapatite. This study introduces a novel, green and facile method for the synthesis of highly porous nano hydroxyapatite (nHA) and its magnetic composite aerogels (SPIONS@nHA) by freeze-drying technology. The synthesized materials have undergone through characterization. Perchlorate removal efficiency of the materials was investigated for the first time and the factors that influence the perchlorate adsorption capacity were explored and optimized. The magnetic composite of nHA showed an excellent separation in the presence of an external magnetic field from contaminated water after adsorption. XPS analysis and zeta potential measurements showed that the main driving force behind the adsorption of perchlorate is ion exchange and ion-pair formation/electrostatic interaction. Very fast removal kinetics was observed and the experimental maximum adsorption capacity for nHA and SPIONS@nHA were 148.4 and 305.8 mgg−1 respectively. It is commendable that other commonly existing ions exhibited no remarkable effect on the adsorption performance, indicating SPIONS@nHA has an immense application potential. The adsorption process was found to follow by pseudo-second-order and intra-particle diffusion kinetic models. A novel method for the regeneration of perchlorate loaded adsorbent using phosphate buffer was also studied in this paper. The regeneration performance of spent magnetic adsorbent showed greater than 90% recovery on the adsorption capacity even after fifth cycle, revealing the stability, reusability and economic efficiency of the adsorbent. Thus, magnetic nanocomposite of the biogenic hydroxyapaptite can be exploited as a sustainable and efficacious material for the abolishment of perchlorate from aqueous media at near neutral pH.

Green Synthesis of copper Nanoparticles: Synthesis, Characterization and their application: About Future

In the present study copper oxide nanoparticles (CuNPs) were synthesized via simple and eco-friendly green route using black tea extract . Characterization of synthesized nanoparticles (NPs) was undertaken. The characteristic absorption peak of CuNPs was in range (352-355) nm in UV–Vis spectrum. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) studies revealed the morphological and structural character of green NPs. The particle size was 25-50 nm. Energy dispersive spectroscopy (EDX) showed high intense metallic peak of copper (Cu), oxygen (O), carbon (C) and low intense peaks of phosphorus (P) , calcium (Ca) , sulfur (S), potassium (K) elements due to the capping action of biomolecules of plant extract in CuNPs formation. The X-ray diffraction (XRD) pattern showed distinctive peaks corresponding to (200), (220) and (311) planes revealing the high crystalline nature of synthesized CuNPs . The dyeing behavior of green CuNPs treated fabric with Acid Black 172 (AB 172) has been studied and the build up of dye, measured as exhaustion percentage (E%). Dye adsorption rate constants according to pseudo-first order, pseudo-second order, and intra-particle diffusion kinetic models were calculated. Moreover, the dye adsorption equilibrium data were fitted well to the Freundlich isotherm rather than Langmuir isotherm. The overall adsorption process follow pseudo-second order kinetics, Intraparticle diffusion and Elovich model. The CuNPs treatment produces a nylon fabric with advanced color fastness and antibacterial properties enabling them to improve human health care and reducing temperature, the environmental impacts, fabric damage, amount of dyestuff used and saving energy of conventional dyeing of nylon fabrics. This review focuses on green synthesis of CuNPs using environmentally benign reagents in minimal time paves the way for future studies on CuNPs toxicity without risking interference from potentially toxic reagents and capping agents. The use of this technique to treat nylon fabric may lead to new coloration technique and other functional improvement.

Sulfamethoxazole Leaching from Manure-Amended Sandy Loam Soil as Affected by the Application of Jujube Wood Waste-Derived Biochar.

Vertical translocation/leaching of sulfamethoxazole (SMZ) through manure-amended sandy loam soil and significance of biochar application on SMZ retention were investigated in this study. Soil was filled in columns and amended with manure spiked with 13.75 mg kg−1 (S1), 27.5 mg kg−1 (S2), and 55 mg kg−1 (S3) of SMZ. Jujube (Ziziphus jujube L.) wood waste was transformed into biochar and mixed with S3 at 0.5% (S3-B1), 1.0% (S3-B2), and 2.0% (S3-B3) ratio. Cumulative SMZ leaching was lowest at pH 3.0, which increased by 16% and 34% at pH 5.0 and 7.0, respectively. A quicker release and translocation of SMZ from manure occurred during the initial 40 h, which gradually reduced over time. Intraparticle diffusion and Elovich kinetic models were the best fitted to leaching data. S3 exhibited the highest release and vertical translocation of SMZ, followed by S2, and S1; however, SMZ leaching was reduced by more than twofold in S3-B3. At pH 3.0, 2.0% biochar resulted in 99% reduction in SMZ leaching within 72 h, while 1.0% and 0.5% biochar applications reduced SMZ leaching to 99% within 120 and 144 h, respectively, in S3. The higher SMZ retention onto biochar could be due to electrostatic interactions, H-bonding, and π-π electron donor acceptor interactions.

Enhancement of the adsorptive performance of TiO2 nanoparticles towards methylene blue by adding suspended nanoparticles of Pt: kinetics, isotherm, and thermodynamic studies

Methylene blue (MB) is one of the most dangerous dyes found in numerous industries’ wastewaters. Thus, the effect of suspended Pt nanoparticles (NPs) on the adsorption capability of TiO2 NPs towards MB was investigated in this research. Factors affecting (adsorbate initial concentration, agitation time, solution pH, and temperature) the adsorption capacity of MB on the modified TiO2 NPs were also studied. It was found that the first two factors have a positive effect, the temperature has an adverse impact, and the maximum uptake was observed when pH is 11. Isotherm parameters of Langmuir, Freundlich, and Timken models were determined. Langmuir’s model was found to be the best one for analyzing the experimental data. The adsorption capacities obtained were 100.61, 90.66, and 80.26 mg g−1 at 25 °C, 40 °C, and 55 °C, respectively. 1st order, 2nd order, and intra-particle diffusion kinetic models were utilized to analyze experimental data. It found that these data were explained well by the 2nd order model, indicating that this adsorption is chemisorption. Thermodynamic parameters were also determined, and the results obtained suggest that this adsorption is an exothermic and spontaneous process. The findings show that TiO2 NPs modified by suspended Pt NPs will get a strong attraction in the treatment of fluids and wastewaters.

Effects of green iron nanoparticles on iron changes and phytoavailability in a calcareous soil

Green iron nanoparticles (Fe NPs) can be a practical solution to combat iron (Fe) deficiency in calcareous agricultural soils. The main aim of the present work was to assess the effects of green Fe NPs on Fe availability in calcareous soils. For this purpose, green Fe NPs were synthesized using green tea (G-Fe NPs), Shirazi thyme (T-Fe NPs), walnut green hull (W-Fe NPs), and pistachio green hull (P-Fe NPs) extracts and applied as a source of Fe fertilizer to sorghum (Sorghum bicolor L. Moench) plants. Results of X-ray diffraction (XRD), scanning electron microscopy (SEM), and dynamic light scattering (DLS) indicated that the green Fe NPs were amorphous in nature and the polyphenols obtained from plant-part extracts acted as both capping and reducing agents. Similar to the behavior of Fe-ethylenediamine-N,N′-bis(2-hydroxyphenyl) acetic acid (Fe-EDDHA) in calcareous soils, G-Fe NPs, T-Fe NPs, W-Fe NPs, and P-Fe NPs increased Fe release compared with the control and FeSO4 treatment. Cumulative Fe release data fitted well to the power function, intra-particle diffusion, and Elovich kinetic models. According to the pot experiment, the increment in soil Fe availability upon Fe-EDDHA and Fe NPs application led to an increase in Fe uptake, growth, and photosynthetic pigment contents of the sorghum plants. Although further research is needed to evaluate the residual effect and environmental impact of green Fe NPs, they may be an appropriate substitute for traditional Fe fertilizers in calcareous soils.

Crystal Violet Removal Study with Natural and Biochar Prina from Aqueous Solutions

Crystal Violet is an inexpensive dyestuff used for silk, leather, paper dyeing and for many different purposes. In addition, culture staining is also frequently used in microbiology. It has a very dense and sticky dye. When the crystal violet dissolves in water, it significantly reduces the light transmittance and disrupts the natural environment balance. Adsorption is a method frequently used in the removal of such dyes. In this study, as an industrial waste, pirina was used as an adsorbent substance with its natural and thermally modified form. By using the pyrolysis method at 700 °C, biochar form of pirina was obtained. Natural and biochar pirina and crystal violet dye have been tried under different adsorption conditions. For this purpose, experiments were carried out at different pirina dosages, different initial dye concentrations and different contact times. The highest removal efficiencies are around 75% in natural pirina, while the biochar is around 98% in pirina. In addition, concentration studies performed against concentration were applied to the Langmuir and Freundlich isotherms and it was found that the adsorption was fit with the Freundlich model. The contact time removal studies were applied to pseudo-first order, pseudo-second order and intraparticle diffusion kinetic models, and adsorption was found to be fit with the pseudo-second order kinetic model. According to the results of the experiment, it was observed that the thermal treatment caused a great increase in the removal efficiency and it was found that it is an efficient adsorbent material that can be used to remove the crystal violet dye from the aqueous solutions.

Smartphone-based study of cement-activated charcoal coatings for removal of organic pollutants from water

Cement-based activated charcoal composites (in the form of coatings) were fabricated and applied as an adsorbent for water remediations. Activated charcoal (AC) was mixed in the Portland cement in different proportions (10, 30, and 50% by wt.) and prepared samples were used as an adsorbent for two different organic compounds, namely Methylene blue (MB), Rhodamine and B (RB). The smartphone-based colorimetry method was used to quantify the dye removal process. The maximum adsorptive removals of MB, RB, and were recorded 80, and 71, respectively using 50% AC coating at neutral pH 7. The operating parameters were optimized using response surface methodology and box-Behnken design was used for experimental design and analysis of results. The coatings composition was found to be the most influencing parameter followed by adsorbate concentration and pH. The maximum removal was found at a dye concentration of 20.1 mg/lt, pH 11.7, and composite composition of 47.9%. The intraparticle diffusion kinetic model was used to study the pore diffusion mechanism.

Methylene Blue Dye Removal from Aqueous Media Using Activated Carbon Prepared by Lotus Leaves: Kinetic, Equilibrium and Thermodynamic Study

In the present work, methylene blue was eliminated from aqueous solution using activated carbon prepared by lotus leaves. To perform the experiments, batch method was applied. Also, several analyses such as SEM, FTIR, EDAX and BET were done to determine the surface properties of the activated carbon. The results showed that the maximum sorption efficiency of 97.59% was obtained in initial dye concentration of 10 mg/L, pH of 9, adsorbent dosage of 4 g/L, temperature of 25 °C, contact time of 60 min and mixture speed of 400 rpm. Furthermore, the maximum adsorption capacity was determined 80 mg/g, which was a significant value. The experimental data was analyzed using pseudo-first order, pseudo-second order and intra-particle diffusion kinetic models, which the results showed that the pseudo-second order kinetic model could better describe the kinetic behavior of the sorption process. Also, the constant rate of the pseudo-second order kinetic model was obtained in the range of 0.0218-0.0345 g/mg.min. Moreover, the adsorption equilibrium was well described using Freundlich isotherm model. Furthermore, the thermodynamic studies indicated that the sorption process of methylene blue dye using the activated carbon was spontaneous and exothermic.

Preparation of hydroxyapatite-calcium ferrite composite for application in loading and sustainable release of amoxicillin: Optimization and modeling of the process by response surface methodology and artificial neural network

In this research, a merit carrier consisting of hydroxyapatite and calcium ferrite (HAp-CaFe2O4) was prepared via a convenient procedure and characterized using a series of techniques, including XRD, FE-SEM, TEM, EDS mapping, BET/BJH, VSM, and TGA. The loading of Amoxicillin (AMX) onto HAp-CaFe2O4 was optimized and modeled by two powerful approaches, namely response surface methodology (RSM) and artificial neural network (ANN). RSM-optimized results demonstrated that the maximum drug loading efficiency was 91.76% at a carrier dosage of 1.2 g, a drug concentration of 30 mg L−1, and a pH of 6.5 within a stipulated time of 60 min. ANN modeling revealed that the pH of the solution had a dramatic effect with a 35% impact on the drug loading process. The downloading of AMX by HAp-CaFe2O4 was consistent with pseudo-2nd order and intra-particle diffusion kinetics models as well as the Temkin isotherm model, implying the chemisorption of the drug molecules on the carrier. The AMX release was evaluated at different pHs, and it was revealed that the sustained and prolonged drug evacuation occurred in the neutral medium as compared to acidic and basic media. The conformity of the drug release kinetics to the Korsmeyer-Peppas model indicated that the Fickian diffusion dominated the AMX release. The MTT assay showed the biocompatibility and safety of HAp-CaFe2O4 toward A549 cell lines.In summary, as-prepared HAp-CaFe2O4 can be regarded as a biocompatible and stimuli-responsive carrier for controlled and targeted drug delivery systems.

Intercalated organo-bentonite as efficient biosorbent for aromatic carboxylic acids from wastewater

This study aims to prepare intercalated organo-bentonite using cetylbenzyldimethylammoniumbromide (CBDAB) and investigate its ability for the removal of benzoic (BA) and salicylic (SA) acids from wastewater. The obtained results confirm the intercalation of CBDA into the bentonite interlayer. Several important parameters of SA and BA adsorption onto sodium bentonite (Na-bent) and intercalated bentonite (CBDA-bent) including the adsorbent dosage, contact time, pH, ionic strength, and temperature are investigated in batch mode. Overall, CBDA-bent, which possesses a high specific surface (32 m2/g) area and a pore volume (0.14 cm3/g) demonstrates promising prospects for SA and BA adsorption, reaching 55.2 mg/g and 64.5 mg/g, respectively. The SA and BA are found to primarily interact well through both surface and interlayer processes in basic media. The equilibrium experimental data have been analyzed by Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich isotherms; nonetheless the adsorption is well described by the Langmuir model. The influence of contact time on SA and BA uptake is modeled using pseudo second-order, pseudo first-order, intraparticle diffusion, and Boyd kinetic models. An intraparticle diffusion mechanism is found to control the adsorption process, where the internal mass transfer is higher than the external mass transfer. A thermodynamic study shows that the adsorption of both acids is not spontaneous and endothermic. Desorption of SA and BA acids from both Na-bent and CBDA-bent has been performed and the possibilities for reuse investigated.

Improved Cd (II) ions removal performance from aqueous solution using cerium doped activated carbon

The present work deals with the removal of Cd (II) ions in aqueous solution using modified activated carbon based palm kernel shells. The activated carbon surface was modified by incorporating cerium atoms. The experiments were performed in batch mode by varying the initial pH solution, adsorbent dose, contact time and initial concentration of Cd (II) ions. The experimental results analysis revealed that the Cd (II) ions removal percentage increased with the increase of the contact time and reached adsorption equilibrium within 150 min with a removal percentage of 51.24%. The adsorbed quantities were strongly linked to the ionic radius and hydration energy of oxides with optimal pH values ranging between 5 and 7 for optimal adsorbent dose of 0.03 g. Six isotherms models were investigated to explain the adsorption equilibrium. The Freundlich and Hasley isotherms models gave the best fit according to their correlation coefficient values R2 > 0.9. Moreover, the value of (1/n) was less than unity indicating the heterogeneity of Ce-doped activated carbon surface. The surface heterogeneity and material porosity were confirmed by scanning electron microscopy. Four kinetics models were used to identify the mechanisms that governed the Cd (II) ions adsorption. The pseudo second order and intraparticle diffusion kinetics models fitted well the experimental data. Both chemisorption and physisorption mechanisms of Cd (II) ions removal were controlled by hydrated radius and the diffusion process into AC-Ce network. Thus, the Ce-doped activated carbon obtained by carbonization/activation of palm kernel shells is an alternative and low-cost adsorbent which can be useful for the remediation of heavy metal contamination resulting from the migration from phosphogypsum production sites to water resources.

The removal of anionic and cationic dyes from an aqueous solution using biomass-based activated carbon

In this study, two biomass-based adsorbents were used as new precursors for optimizing synthesis conditions of a cost-effective powdered activated carbon (PAC). The PAC removed dyes from an aqueous solution using carbonization and activation by KOH, NaOH, and H2SO4. The optimum synthesis, activation temperature, time and impregnation ratio, removal rate, and uptake capacity were determined. The optimum PAC was analyzed and characterized using Fourier-transform infrared spectroscopy (FTIR), x-ray diffraction (XRD), a field emission scanning electron microscope (FESEM), Zeta potential, and Raman spectroscopy. Morphological studies showed single-layered planes with highly porous surfaces, especially PAC activated by NaOH and H2SO4. The results showed that the experimental data were well-fitted with a pseudo-second-order model. Based on Langmuir isotherm, the maximum adsorption capacity for removing methylene blue (MB) was 769.23 mg g−1 and 458.43 mg g−1 for congo red (CR). Based on the isotherm models, more than one mechanism was involved in the adsorption process, monolayer for the anionic dye and multilayer for the cationic dye. Elovich and intraparticle diffusion kinetic models showed that rubber seed shells (RSS) has higher α values with a greater tendency to adsorb dyes compared to rubber seed (RS). A thermodynamic study showed that both dyes’ adsorption process was spontaneous and exothermic due to the negative values of the enthalpy (ΔH) and Gibbs free energy (ΔG). The change in removal efficiency of adsorbent for regeneration study was observed in the seventh cycles, with a 3% decline in the CR and 2% decline in MB removal performance. This study showed that the presence of functional groups and active sites on the produced adsorbent (hydroxyl, alkoxy, carboxyl, and π − π) contributed to its considerable affinity for adsorption in dye removal. Therefore, the optimum PAC can serve as efficient and cost-effective adsorbents to remove dyes from industrial wastewater.

Novel 3D flower like ZnO/MnV2O6 heterojunction as an efficient adsorbent for the removal of imidacloprid and photocatalyst for degradation of organic dyes in waste water

In this investigation, a novel 3D flower like ZnO/MnV2O6 heterojunction was successfully constructed via facile hydrothermal method, and employed to remove most consumable imidacloprid pesticide and photocatalytic degradation of methylene blue (MB) and methyl orange (MO) dyes in aqueous system. The photocatalytic activities of the heterojunction samples with different dosage were estimated by UV–vis spectroscopy. Nearly, 95.2% of MB and 91.8% of MO dye was decomposed in 60 and 90 min, respectively. The 3D flower like ZnO/MnV2O6 heterojunction demonstrated 99% adsorption for imidacloprid in 200 min. The effect of diverse factors like pH, contact time and adsorbent dosage on adsorption was investigated. The highest removal efficiency was observed at pH 4 with 0.03 g of adsorbent. The kinetic data was fitted into pseudo first and second order, and intraparticle diffusion kinetics models. It was observed that the data for adsorption of imidacloprid on ZnO/MnV2O6 heterojunction fits better into pseudo second order kinetic model. The adsorption isotherms fit well into Langmuir adsorption isotherm model than Freundlich and Temkin models. The maximum adsorption capacity of S-I (0.01 g), S-II (0.02 g), S-III (0.03 g) & S-IV (0.05 g) samples was observed as 81.3, 89.3, 128.2 and 147.1 mg g−1, respectively.

RETRACTED ARTICLE: Kinetic, isotherm, thermodynamic and mechanism investigations of dihydrogen phosphate removal by MgAl-LDH

In this study, Mg–Al layered double hydroxide (MgAl-LDH) was synthesized by the urea hydrolysis method and used as sorbent to remove phosphate from aqueous solutions. Structural and morphological studies show that MgAl-LDH was prepared successfully with good crystallinity. The influences of sorbent dosage, time, initial concentrations, solution pH, temperature and competitive ions on the phosphate uptake have been investigated. It has been found that the uptake of phosphate onto MgAl-LDH was rapid and reached equilibrium within 60 min. The kinetic data were studied in terms of the pseudo-first-order, pseudo-second-order, elovich and intraparticle diffusion kinetic models. The pseudo-second-order model best described the sorption process. The isothermal data are best fitted by Freundlich, suggesting that multiple processes may control the adsorption of phosphate on the MgAl-LDH. The maximum adsorption capacity at 25 °C was found to be 346.4 mg/g. The sorption mechanism of phosphate onto LDHs could be via electrostatic attraction, ligand exchange and ion exchange. Phosphates ion uptake in the presence of other ions decreases in the order NO3− > Cl− > SO42−. Thermodynamic experiments suggested that the phosphate adsorption was spontaneous (− ΔG°) and endothermic (+ ΔH°) and increased the randomness (+ ΔS°) in the system. Thus, MgAl-LDH prepared by urea hydrolysis method is an effective sorbent for the removal of phosphate from aqueous solutions.

Adsorption and photocatalytic activity of biosynthesised ZnO nanoparticles using Aloe Vera leaf extract

In this article, we demonstrates the growth of phase pure ZnO nanostructures from Aloe-Vera leaf extract and degradation of an organic dye-Malachite Green (MG)- from aqueous medium using the same as catalyst. Adsorption mechanisms were evaluated using Lagergren’s pseudo-first-order, pseudo-second-order and intraparticle diffusion kinetic models. X-Ray diffraction data showed that the synthesised ZnO is crystalline with hexagonal wurtzite phase. Average crystallite size and lattice strain was estimated from Scherrer equation and Williamson-Hall analysis with the help of Rietveld refinement data. Crystallite size obtained from Scherrer method is 12.62 nm while that from Williamson-Hall analysis is 19.27 nm. Uniform growth of ZnO nano-sheets were confirmed by FE-SEM analysis. Optical characterisation was carried by UV-Visible spectroscopy and the band gap ZnO nanoparticles was found to be 3.19 eV. Zn-O stretching vibrations were recorded at 550 cm−1 using FTIR spectrophotometer. Results showed that biosynthesised ZnO nanosheets are particularly effective for the degradation of MG dye.

Preparation of a Novel Cellulose-Styrene Copolymer Adsorbent and Its Adsorption of Nitrobenzene from Aqueous Solutions.

A novel cellulose–styrene copolymer adsorbent (cellulose-St) was prepared using free radical polymerization. Successful polymerization was confirmed through Fourier Transform Infrared Spectroscopy (FTIR), Carbon 13 Solid Nuclear Magnetic Resonance (13C NMR) Spectroscopy, Scanning Electron Microscopy (SEM), etc. Cellulose-St possessed good hydrophobicity, and the best water contact angle of cellulose-St samples could reach 146°. It had the ability of adsorption for nitrobenzene (NB), and the adsorption process could be well described by the pseudo-second-order (R2 > 0.99) and three-stage intraparticle diffusion (R2 > 0.99) kinetic models. Furthermore, the dynamic adsorption experiments revealed that cellulose-St had the potential for continuous separation of NB in water, and the breakthrough point for the initial NB concentration of 10 mg/L reached 1.275 L/g. Moreover, cellulose-St exhibited excellent environmental adaptability that it could maintain its hydrophobicity and adsorption ability for NB in strong acids, strong alkalis, or organic solvents. The used cellulose-St could be reused after washing with ethanol and keep almost constant adsorption capacity after ten cycles.

Adsorption of metals from oil sands process water (OSPW) under natural pH by sludge-based Biochar/Chitosan composite

Some metals in oil sands process water (OSPW) are potential threats to human health and the environment. Hence, the removal of excess metals from OSPW is of great significance. In this study, anaerobic sludge waste from a wastewater treatment plant, was reused to prepare sludge-based biochar. A Biochar/Chitosan (Biochar/CS) adsorbent with excellent removal efficiency for metals (Cr, Cu, Se and Pb) in real OSPW was prepared through a facile hydrothermal method. The structural properties of the synthesized Biochar/CS composite were characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM) and Brunauer–Emmett–Teller (BET) method. This study reports for the first time the removal of metals from OSPW under natural pH using Biochar/CS adsorbent. The composite exhibited a higher removal efficiency towards Cr (83.9%), Cu (97.5%), Se (87.9%) and Pb (94.3%) when the initial concentrations of Cr, Cu, Se and Pb were 0.02914, 0.06185, 0.00800 and 0.00516 mg/L, respectively, at a dosage of 0.5 g/L, compared with biochar or chitosan alone. The possible adsorption mechanism was proposed, and the enhanced removal ability was due to the improved specific surface area and pore volume, which increased by about 20 and 14 times as compared with chitosan. Functional groups in the composite, such as –NH2, -OH and some oxygen containing groups, were also responsible for the enhanced removal ability, which also might be the reason for the better performance of the composite than biochar alone due to the lack of functional groups on the biochar. Moreover, the adsorption process was best modelled by the Freundlich model, pseudo second order and intraparticle diffusion kinetic models. The results indicated that chemical adsorption might play the dominant role in the removal process. Overall, the Biochar/CS composite would be a promising and effective adsorbent for metals removal, owing to its advantages of being cost-effective and environmentally friendly.

Effects of catalysts on structural and adsorptive properties of iron oxide-silica nanocomposites

Iron oxide-silica nanocomposites were prepared by sol-gel method using ammonia (NH3), acetic acid (CH3COOH) and hydrochloric acid (HCl) catalysts to generate different pH values for the reaction conditions. As starting precursors, for the silica, respectively, for the iron oxide, tetraethylorthosilicate (TEOS) and iron-III-acetylacetonate were used. The physico-chemical characterization of the materials revealed that the sample obtained with HCl catalyst displays the largest surface area (300 m2/g), the most compact network structure, highest surface roughness, biggest crystallite size (14 nm), magnetization (7 emu/g) and superparamagnetic behavior. These materials were tested for adsorption of Cr6+ and Zn2+ from aqueous solution. Sample M-HCl presented the highest surface area and was further used for adsorption of metal ions. Kinetic, thermodynamic and equilibrium adsorption measurements studies were made for Cr6+ and Zn2+. To establish the material behavior from a thermodynamic point of view, temperature and contact time of adsorption process, activation energy, free energy, of standard enthalpy and entropy were calculated. The kinetic behavior was modelled by pseudo-first-order, pseudo-second-order and intraparticle diffusion kinetic models and the adsorption characteristics were determined by modelling the experimental data with Langmuir, Freundlich and Sips isotherms.