State-of-the-art predictive modeling of heavy metal ions removal from the water environment using nanotubes.

In this research, molecular dynamics (MD) simulation is used to investigate the efficiency of carbon nanotubes (CNT) and boron nitride nanotubes (BNNT) in removing lead ions from contaminated waters. Then the effect of functionalizing nanotubes with -COO- and COOH- functional groups and the nanotubes' absorption performance of two different concentrations of lead ions are studied. To better evaluate adsorption process, the set of descriptors, such as interaction energies, radial distribution function, etc., are calculated. The MD results show that the absorption performance is significantly improved by modifying the surface of CNT and BNNT with functional groups. In addition, the adsorption capacity increases in higher concentrations of Pb ions at BNNTCOO- and CNTCOOH systems. The interaction energy of BNNTCOO- with a concentration of 50 lead ions is - 2879.28 kJ/mol, which is about 106 kJ/mol more negative than BNNTCOO- at a concentration of 20 lead ions. Also, it is observed that the functionalization of both nanotubes with -COO- increases their absorption capacity. The obtained results from this study provide significant information about the mechanisms of lead adsorption on the surface of nanotubes.

A comprehensive study on the adsorption-photocatalytic processes using CoFe2O4/SiO2/MnO2 magnetic nanocomposite as a novel photo-catalyst for removal of Cr (VI) under simulated sunlight: Isotherm, kinetic and thermodynamic studies.

Purpose: The present study aimed to investigate the efficiency of CoFe2O4/SiO2/flower-like MnO2 nanoparticles as a catalyst for Cr (VI) adsorption-photocatalytic processes. Methods: The magnetic nanocomposite used was first synthesized and then characterized using TEM, SEM, EDX, XRD, FTIR, XRF and BET advanced techniques. The removal of the Cr (VI) was performed through a batch adsorption approach and the effects of sample pH (A; 2-6), initial chromate concentration (B; 50-100 ppm) and adsorbent weight to sample volume ratio (C; 1-3 mg ml-1), hole scavenger (0.1 -0.3%w/v) and time (E; 30-60 min), to evaluate the individual and interactive effects under ultraviolet light conditions, were also studied by the central composite design in the photocatalytic process of adsorption. Results: The adsorption-photocatalytic performance of the CoFe2O4/SiO2/MnO2 composite was high in which 98.1% of Cr(VI) after 30 min of photocatalytic treatment in optimum conditions (i.e. pH = 3, catalyst concentration = 2 mg L-1, Cr(VI) concentration = 200 mg L-1, and hole scavenger concentration = 0.4% (w/ v), At laboratory temperature, speed = 400 rpm, under UV radiation).Under optimum conditions, Cr(VI) reductive followed pseudo-second-order kinetics and followed the Langmuir and Temkin isotherms, also, positive value of ΔH° indicates endothermic nature. Conclusions: The results showed that the synthesized CoFe2O4/SiO2/MnO2 magnetic nanocomposite holds a great potential for use as a photocatalyst to remove Cr (VI) in adsorption reactions. It can be used as an effective catalyst in the eradication of Cr (VI) wastewater. Supplementary Information: The online version contains supplementary material available at 10.1007/s40201-021-00763-1.

Gel electro-membrane extraction of propranolol and atenolol from blood serum samples: Effect of graphene-based nanomaterials on extraction efficiency of gel membrane.

In this work, gel electro-membrane extraction (G-EME) method is suggested for extraction and determination of propranolol and atenolol in complex biological samples. An in-house membrane based on agarose was used as green and biodegradable gel membrane. Essential chemical parameters that influence on extraction efficiency were tested, optimized and evaluated via a central composite design (CCD) and response surface methodology (RSM). Optimal conditions for extraction of drugs from the 7.0 mL sample were as follows: 3% (w/v) agarose with 0.1% (v/v) acetic acid functioning as membrane, voltage: 50 V; pH of the donor phase (DP): 8.1; pH of the AP: 3.3; extraction time: 35.9 min. Under these conditions, the acceptable normalized extraction recoveries were obtained such as 71.9 ± 5.4% that were in good agreement with the predicted values (i.e., 73.1 ± 0.9%). Limits of detection (LODs) for propranolol and atenolol were 5.0 ng mL-1 and 7.5 ng mL-1, respectively. Moreover, for the first time, the effect of presence of four graphene-based nanomaterials such as graphene (G), graphene oxide (GO), three-dimensional nitrogen doped graphene oxide (3D-ND-GO) and high nitrogen doped graphene oxide (HND-GO) in agarose gel membrane on extraction efficiency, was investigated. The results showed that in presence of these nanomaterials, the normalized recovery depressed significantly due to increasing of electric current and electroendosmosis (EEO) phenomenon. Eventually, the proposed method was applied to quantify basic drugs in real plasma samples with relative recoveries in the range of 85.7-97.5%, indicating good reliability of the assay.

Immobilizing magnetic glutaraldehyde cross-linked chitosan on graphene oxide and nitrogen-doped graphene oxide as well-dispersible adsorbents for chromate removal from aqueous solutions.

Glutaraldehyde cross-linked chitosan with an Fe3O4 core was prepared and immobilized on the graphene oxide and nitrogen-doped graphene oxide surfaces to achieve magnetic nanocomposites as excellent adsorbents for removal of chromate. The prepared magnetic nanocomposite adsorbents were characterized. Then, the applicability of these nanocomposites for adsorptive removal of chromate was investigated and the adsorption conditions were optimized. In this regard, to determine the relationship between effective parameters on chromate adsorption, the response surface methodology was applied. The statistical parameters of the resulting models were checked and confirmed that the predicted adsorption efficiencies were in good agreement with the experimental values. For removing of 50 ppm chromate, the pH of 2 and 3, the adsorbent dose of 4 and 2.7 mg mL-1 and contact time of 60 and 45 min were defined as optimum for MCC@GO and MCC@NGO, respectively. We found that kinetic data followed a pseudo second-order kinetic model. The evaluation of adsorption equilibrium isotherms models was conducted and it was found out the latter two fit well, reflecting the monolayer adsorption of the chromate molecules on the nanocomposites. Finally, the adsorption tests on real aqueous samples indicated the capability of these nanocomposites in removing over 90% of chromate ions.

Modified nickel ferrite nanocomposite/functionalized chitosan as a novel adsorbent for the removal of acidic dyes.

As a new type of magnetic adsorbent, a nickel ferrite nanocomposite modified by functionalized chitosan was developed to remove methyl orange and Congo red from aqueous solutions. This new adsorbent was characterized and utilizing batch adsorption approach, the mechanism of methyl orange and Congo red removal were probed. Following that the study on pertinent parameters which could influence the efficiency of the dyes removal, i.e. pH of the solution, initial dye concentration, dose of the adsorbent, and contact time were accomplished in order to arrive their optimized values by using response surface methodology. In addition, kinetics and isotherm studies were conducted on the developed system. Langmuir model was used to probe adsorption isotherm, acquiring adsorption capacity of 551.2 and 274.7 mg g-1 for methyl orange and Congo red, respectively. Both of methyl orange and Congo red adsorption kinetics obeyed a pseudo-second-order kinetic model, indicating that adsorption was the rate-limiting step and only 5 min was required to remove 50% of dyes. The fitting of experimental data was fulfilled with intra-particle diffusion reaching to conclusion that the adsorption kinetic could be controlled simultaneously by film diffusion and intra-particle diffusion. Furthermore, the desorption studies of dyes showed that the adsorbent is reusable.

Preconcentration and speciation of trace amounts of chromium in saline samples using temperature-controlled microextraction based on ionic liquid as extraction solvent and determination by electrothermal atomic absorption spectrometry.

A sensitive and selective method for the preconcentration and speciation of sub ng L(-1) levels of chromium species in aqueous solutions with high salt contents is described. The developed method is based on temperature-controlled microextraction of chromium species using the 1-hexyl-3-methylimidazolium hexafluorophosphate ([HMIM][PF(6)]) ionic liquid as an extractant followed by electrothermal atomic absorption spectrometry (ETAAS) determination. The extraction of chromium species from aqueous solution into the fine droplets of [HMIM][PF(6)] was performed with ammonium pyrrolidine dithiocarbamate (APDC) as the chelating agent. Some predominant factors affecting the preconcentration and speciation of both Cr(III) and Cr(VI) species were evaluated and optimized. Under the optimum conditions, the calibration graphs were linear over the concentration ranges from 50 to 200 ng L(-1) for Cr(III) and from 25 to 150 ng L(-1) for Cr(VI). The limits of detection (LOD) of the developed method were 5.40 ng L(-1) and 2.45 ng L(-1) for Cr(III) and Cr(VI) ions, respectively. The enrichment factor for chromium species was found to be 42. The relative standard deviations for six replicate determinations of 100 ng L(-1) of either Cr(VI) or Cr(III) were 4.24% and 3.05%, respectively. The developed method was successfully applied to the speciation and determination of chromium species in water and urine samples.