Hamedreza Javadian

Adsorption kinetics, isotherm, and thermodynamics of Hg 2+ to polyaniline/hexagonal mesoporous silica nanocomposite in water/wastewater

A nanocomposite of polyaniline/hexagonal mesoporous silica (PAN/HMS) was prepared and characterized by BET analysis, transmission electron microscopy, and FT-IR spectra. Batch adsorption results showed that PAN/HMS had high affinity to Hg2+ in aqueous solutions. Various factors affecting the adsorption capacity such as contact time, temperature, absorbent dosage, pH, and initial concentration of Hg2+ ions were investigated. The adsorption kinetics for the Hg2+ showed that the adsorption reached equilibrium within 8xa0min and adsorption rates followed the pseudo-second-order rate law, indicating chemical sorption as the rate-limiting step of the adsorption mechanism. Sorption of Hg2+ to PAN/HMS agreed well to the Langmuir adsorption model at different ionic strengths with the maximum adsorption capacity of 843xa0mgxa0g−1 (Ixa0=xa01000xa0mgxa0L−1) at pH 10. Thermodynamic studies revealed that the adsorption of Hg2+ ions was spontaneous, exothermic processes with an increase of entropy. The recovery of the Hg2+ from the adsorbent was found to be more than 88xa0% using H2SO4 (0.1xa0M), and the ability of the absorbent to be reused was investigated.

Kinetic and equilibrium study of Ni(II) sorption from aqueous solutions onto Peganum harmala-L

AbstractnIn this study, the adsorption behavior of Ni(II) in an aqueous solution system using natural adsorbent Peganum harmala-L was measured via batch mode. The prepared sorbent was characterized by scanning electron microscope, Fourier transform infrared spectroscopy, N2 adsorption–desorption and pHzpc. Adsorption experiments were carried out by varying several conditions such as contact time, metal ion concentration and pH to assess kinetic and equilibrium parameters. The equilibrium data were analyzed based on the Langmuir, Freundlich, Temkin and Dubinin–Radushkevich isotherms. Kinetic data were analyzed using the pseudo-first-order, pseudo-second-order and intra-particular diffusion models. Experimental data showed that at contact time 60xa0min, metal ion concentration 50xa0mg/L and pH 6, a maximum amount of Ni(II) ions can be removed. The experimental data were best described by the Langmuir isotherm model as is evident from the high R2 value of 0.988. The adsorption capacity (qm) obtained was 68.02xa0mg/g at an initial pH of 6 and a temperature of 25xa0°C. Kinetic studies of the adsorption showed that equilibrium was reached within 60xa0min of contact and the adsorption process followed the pseudo-first-order model. The obtained results show that P. harmala-L can be used as an effective and a natural low-cost adsorbent for the removal of Ni(II) from aqueous solutions.

Synthesis of Fe3O4@CuS@Ni2P-CNTs magnetic nanocomposite for sonochemical-assisted sorption and pre-concentration of trace Allura Red from aqueous samples prior to HPLC-UV detection: CCD-RSM design

A simple procedure based on ultrasound-assisted (UA) dispersive micro solid phase extraction (D-μ-SPE) was applied for sorption of trace amount Allura Red (AR) in fruit juice and water samples. After loading process by UA-D-μ-SPE, the concentrated AR was eluted and monitored using high-performance liquid chromatography-ultraviolet -visible detector (HPLC-UV). The best operational conditions were obtained as follows: pHu202f=u202f3.0, 8u202fmg of the sorbent, sonication time of 4.5u202fmin and 0.16u202fmL of THF as elution solvent. Under the optimum operational conditions, the present method was acceptable for AR quantification in the range of 1.0-5000u202fngu202fmL-1. The repeatability based on RSD with the amount of 1.67-3.18%, low LOD (0.198u202fngu202fmL-1) and LOQ (0.659u202fngu202fmL-1) were obtained. The UA-D-μ-SPE-HPLC-UV method was successfully applied for trace quantification of AR from water and commercial fruit juice samples supplied from local supermarkets, and acceptable relative recoveries over the range of 97.7-105.4% with RSDs ≤5.50% were obtained.

Fixed-bed column performances of azure-II and auramine-O adsorption by Pinus eldarica stalks activated carbon and its composite with zno nanoparticles: Optimization by response surface methodology based on central composite design

A continuous adsorption was used for removal of azure II (AZ II) and auramine O (AO) from aqueous solutions using Pinus eldarica stalks activated carbon (PES-AC) from aqueous solutions. The effects of initial dye concentration, flow rate, bed height and contact time on removal percentage of AO and AZ II were evaluated and optimized by central composite design (CCD) at optimum pHxa0=xa07.0. ZnO nanoparticles loaded on activated carbon were also used to remove AO and AZ II at pHxa0=xa07.0 and other optimum conditions. The breakthrough curves were obtained at different flow rates, initial dye concentrations and bed heights and the experimental data were fitted by Thomas, Adams-Bohart and Yoon-Nelson models. The main parameters of fixed-bed column including its adsorption capacity at breakthrough point (qb), adsorption capacity at saturation point (qs), mass transfer zone (MTZ), total removal percentage (R%), and empty bed contact time (EBCT) were calculated. The removal percentages calculated for AZ II and AO II were in the range of 51.6-61.1% and 40.6-61.6%, respectively. Bed adsorption capacity (N0) and critical bed depth (Z0) were obtained by BDST model.

Microwave-induced H2SO4 activation of activated carbon derived from rice agricultural wastes for sorption of methylene blue from aqueous solution

AbstractActivated carbon derived from the rice straw was used for the rapid removal and fast adsorption of methylene blue (MB) from the solvent phase of the aqueous solution. The developed adsorbent was characterized using various analytical techniques such as scanning electron microscopy and FTIR. The effect of various influential parameters including solution pH, adsorbent dosage, contact time, initial adsorbate concentration, stirring speed, and temperature on MB removal were well investigated and optimized. The experimental optimized data showed that a maximum amount of MB ions can be removed at contact time 25xa0min, dye ion concentration 40xa0mg/L, and pH of 7. The obtained results of the isotherm study revealed that adsorption data was in good agreement with Langmuir isotherm model (with R2 value of 0.988 and maximum adsorption capacity of 62.5xa0mg/g at initial pH of 7 and temperature of 298xa0K). The negative values of ΔG° and the positive values of ΔH° (22.73xa0kJ/mol) and ΔS° (104xa0J/molxa0K) showed that th...

Cu- and S- @SnO 2 nanoparticles loaded on activated carbon for efficient ultrasound assisted dispersive µSPE-spectrophotometric detection of quercetin in Nasturtium officinale extract and fruit juice samples: CCD-RSM design

A simple, rapid, and efficient method of dispersive micro solid phase extraction (D-μ-SPE) combined with UV-Vis spectrophotometry via ultrasound-assisted (UA) was applied for the determination and preconcentration of quercetin in extract of watercress (Nasturtium officinale), fruit juice and water samples. The sorbent in this method was synthesized by doping copper and sulfide into the tetragonal structure of SnO2-nanoparticles (Cu- and S- @SnO2-NPs) and subsequently loading it on activated carbon (AC). The D-μ-SPE parameters with direct effect on the extraction efficiency of the targeted analyte, such as sample pH, volume of eluent, sorbent mass and ultrasound time were optimized using central composite design method. Under optimized conditions, the calibration graph for quercetin was linear in the range of 20-4000u202fngu202fmL-1; the limit of detection and quantitation were 4.35 and 14.97u202fngu202fmL-1, respectively and the enrichment factor was 95.24. Application of this method to analyze spiked extract, fruit juice and water samples resulted in acceptable recovery values ranging from 90.3% to 97.28% with intra-day and inter-day relative standard deviation values lower than 6.0% in all cases. Among the equilibrium isotherms tested, Langmuir was found to be the best fitted model with maximum sorption capacity of 39.37u202fmgu202fg-1, suggesting a homogeneous mode of sorption for quercetin.

Ultrasound-assisted extraction of antimicrobial compounds from Thymus daenensis and Silybum marianum: Antimicrobial activity with and without the presence of natural silver nanoparticles

The present study is devoted to prepare a new antibacterial and antifungal agent based on in situ-synthesized silver nanoparticles at room temperature using Rosmarinus officinalis (R. officinalis) leaf extract. The Ag-NPs characterization by UV-visible, SEM, TEM and XRD revealed that the particles sizes were in the range of 10-33u202fnm. In this study, hydroalcoholic extracts were used with ultrasonic method. Ultrasonication has recently received attention as a novel bioprocessing tool for process intensification in many areas of downstream processing. The antimicrobial activities of T. daenensis and S. marianum extracts with and without the presence of Ag-NPs were investigated at concentrations from 12.5 to 50u202fmg/mL against Staphylococcus aureus (S. aureus, Gram-positive organism) and Escherichia coli (E. coli, Gram-negative organism), and fungal strains were Aspergillus oryzae (A. oryzae) and Candida albicans (C. albicans). Antimicrobial activity determined using agar disc diffusion method revealed that the activities of Ag-NPs/T. daenensis were superior to Ag-NPs/S. marianum and extracts (T. daenensis and S. marianum). The medicinal plant extract can be used to synthesize the Ag-NPs as an eco-friendly and inexpensive method in large scale. The results showed that the prepared Ag-NPs/extracts as good antibacterial and antifungal agents can be potentially applied against rapidly increasing of antibiotic resistance.

Fuzzy logic modeling of Pb (II) sorption onto mesoporous NiO/ZnCl2-Rosa Canina-L seeds activated carbon nanocomposite prepared by ultrasound-assisted co-precipitation technique

In this study, NiO/Rosa Canina-L seeds activated carbon nanocomposite (NiO/ACNC) was prepared by adding dropwise NaOH solution (2mol/L) to raise the suspension pH to around 9 at room temperature under ultrasonic irradiation (200W) as an efficient method and characterized by FE-SEM, FTIR and N2 adsorption-desorption isotherm. The effect of different parameters such as contact time (0-120min), initial metal ion concentration (25-200mg/L), temperature (298, 318 and 333K), amount of adsorbent (0.002-0.007g) and the solutions initial pH (1-7) on the adsorption of Pb (II) was investigated in batch-scale experiments. The equilibrium data were well fitted by Langmuir model type 1 (R2>0.99). The maximum monolayer adsorption capacity (qm) of NiO/ACNC was 1428.57mg/L. Thermodynamic parameters (ΔG°, ΔH° and ΔS°) were also calculated. The results showed that the adsorption of Pb (II) onto NiO/ACNC was feasible, spontaneous and exothermic under studied conditions. In addition, a fuzzy-logic-based model including multiple inputs and one output was developed to predict the removal efficiency of Pb (II) from aqueous solution. Four input variables including pH, contact time (min), dosage (g) and initial concentration of Pb (II) were fuzzified using an artificial intelligence-based approach. The fuzzy subsets consisted of triangular membership functions with eight levels and a total of 26 rules in the IF-THEN approach which was implemented on a Mamdani-type of fuzzy inference system. Fuzzy data exhibited small deviation with satisfactory coefficient of determination (R2>0.98) that clearly proved very good performance of fuzzy-logic-based model in prediction of removal efficiency of Pb (II). It was confirmed that NiO/ACNC had a great potential as a novel adsorbent to remove Pb (II) from aqueous solution.

Ultrasound-accelerated synthesis of gold nanoparticles modified choline chloride functionalized graphene oxide as a novel sensitive bioelectrochemical sensor: Optimized meloxicam detection using CCD-RSM design and application for human plasma sample

In this research, gold nanoparticles modified choline chloride functionalized graphene oxide (AuNPs-ChCl-GO) was synthesized through the assistance of ultrasound and fabricated as a novel bioelectrochemical sensor and utilized for the sensitive detection of meloxicam (MEL). The morphological and structural features of the AuNPs-ChCl-GO were characterized using different techniques including FTIR, TEM, FE-SEM, EDX, and XRD. The modified electrode showed a remarkable improvement in the anodic oxidation activity of MEL due to the enhancement in the current response compared to the bare carbon paste electrode (CPE). The biosensor composition and measurement conditions were optimized using an experimental design. The differential pulse voltammetry (DPVs) exhibited expanded linear dynamic in the range of 9.0u202f×u202f10-9 to 8.5u202f×u202f10-7u202fM for MEL in Britton-Robinson buffer at pHu202f=u202f4.0 with a detection limit of 1.008u202f×u202f10-9u202fM. The practical utility of the modified electrode was demonstrated by the accurate detection of MEL in human plasma sample.

Synthesis of poly(acrylamide-co-itaconic acid)/MWCNTs superabsorbent hydrogel nanocomposite by ultrasound-assisted technique: Swelling behavior and Pb (II) adsorption capacity

In this research, the poly (acrylamide-co-itaconic acid)/multi-walled carbon nanotubes (P(AAm-co-IA)/MWCNTs) as a novel superabsorbent hydrogel nanocomposite was synthesized by graft copolymerization of acrylamide (AAm) and itaconic acid (IA) mixture in the presence of the MWCNTs using ammonium persulfate (APS) as a free radical initiator and methylenebisacrylamide (MBA) as a crosslinker under ultrasound-assisted condition. The blank P(AAm-co-IA) hydrogel and its composite with the MWCNTs were characterized by means of SEM, FTIR, XRD and TGA methods. The effects of different parameters such as pH, time, the MWCNTs content and salt solutions on swelling behavior were investigated. The stability of the hydrogel increased by any increase in the MWCNTs content, which might be attributed to the hydrophobic nature of the MWCNTs as well as the increase of the crosslinker density. The water retention capacity (WRC) of the P(AAm-co-IA) hydrogel increased in the presence of the MWCNT (10u202fwt%). The synthesized hydrogel nanocomposite was studied for Pb (II) adsorption from aqueous solution. The effects of different parameters such as contact time (5-90u202fmin), Pb (II) initial concentration (25-175u202fmg/L) and initial pH (1.5-4.5) of solution on Pb (II) adsorption were investigated by batch method. In comparison to P(AAm-co-IA) hydrogel, the P(AAm-co-IA)/MWCNTs hydrogel nanocompoite showed better adsorption behavior toward Pb (II). One of the most important aspects of this research was to investigate the effects of ultrasonic waves on polymer matrix and its ability.