Applications of CTAB modified magnetic nanoparticles for removal of chromium (VI) from contaminated water

Support based metal incorporated layered nanomaterials for photocatalytic degradation of organic pollutants

An effective approach to producing sophisticated miniaturized and nanoscale materials involves arranging nanomaterials into layered hierarchical frameworks. Nanostructured layered materials are constructed to possess isolated propagation assets, massive surface areas, and envisioned amenities, making them suitable for a variety of established and novel applications. The utilization of various techniques to create nanostructures adorned with metal nanoparticles provides a secure alternative or reinforcement for the existing physicochemical methods. Supported metal nanoparticles are preferred due to their ease of recovery and usage. Researchers have extensively studied the catalytic properties of noble metal nanoparticles using various selective oxidation and hydrogenation procedures. Despite the numerous advantages of metal-based nanoparticles (NPs), their catalytic potential remains incompletely explored. This article examines metal-based nanomaterials that are supported by layers, and provides an analysis of their manufacturing, procedures, and synthesis. This study incorporates both 2D and 3D layered nanomaterials because of their distinctive layered architectures. This review focuses on the most common metal-supported nanocomposites and methodologies used for photocatalytic degradation of organic dyes employing layered nanomaterials. The comprehensive examination of biological and ecological cleaning and treatment techniques discussed in this article has paved the way for the exploration of cutting-edge technologies that can contribute to the establishment of a sustainable future.

Capping Agents Enable Well-Dispersed and Colloidally Stable Metallic Magnesium Nanoparticles

Mg nanoparticles are an emerging plasmonic material due to Mg's abundance and ability to sustain size- and shape-dependent localized surface plasmon resonances across a broad range of wavelengths from the ultraviolet to the near infrared. However, Mg nanoparticles are colloidally unstable due to their tendency to aggregate and sediment. Nanoparticle aggregation can be inhibited by the addition of capping agents that impart surface charges or steric repulsion. Here, we report that the common capping agents poly(vinyl) pyrrolidone (PVP), polyethylene glycol (PEG), cetyltrimethylammonium bromide (CTAB), and sodium dodecyl sulfate (SDS) interact differently and have varied effects on the aggregation and colloidal stability of Mg nanoparticles. Nanoparticles synthesized in the presence of PVP showed improvements in colloidal stability and reduced aggregation, as observed by electron microscopy and optical spectroscopy. The binding of PVP was confirmed through infrared and X-ray photoelectron spectroscopy. The influence of PVP on the reduction of di-n-butyl magnesium was evaluated through analysis of particle size distribution and Mg yield as a function of reaction time, reducing agent, and temperature. Furthermore, the presence of PVP drastically changes the growth pattern of metallic Mg structures obtained from the reduction of the Grignard reagents butylmagnesium chloride and phenylmagnesium chloride by lithium naphthalenide: large polycrystalline aggregates and well-separated faceted nanoparticles grow without and with PVP, respectively. This study provides new synthetic routes that generate colloidally stable and well-dispersed Mg nanoparticles for plasmonic and other applications.

Efficient adsorption of Cr (VI) onto hematite nanoparticles: ANN, ANFIS modelling, isotherm, kinetic, thermodynamic studies and mechanistic insights

Hematite nanoparticles (AF-Fe2O3NPs) were prepared through a simple method utilizing Acacia falcata leaf extract in this investigation. The nanoparticles were extensively characterized to understand their specific properties. FESEM images revealed agglomerated surface morphology, while EDS confirmed the existence of elemental components, including Fe, O, and C. The mesoporous nature of AF-Fe2O3NPs with a pore diameter of 3.77 nm was determined through BET studies. XRD analysis indicated the crystallinity, with lattice parameters characteristic of hematite nanoparticles (a = 0.504 nm and c = 1.381 nm). Superparamagnetic property of the AF-Fe2O3NPs was affirmed from the saturation magnetization (2.98 emu/g) without any hysteresis. Subsequently, AF-Fe2O3NPs were used as adsorbent for the removal of Cr (VI) from aqueous solution. The experimental data were subjected to machine learning (ML) models, specifically ANN and ANFIS, to predict Cr (VI) removal. Both ML models exhibited excellent predictive capabilities, with high R2 values (>0.99) and low error indices such as MSE, RMSE, and MAE. Furthermore, comprehensive kinetic, isotherm, and thermodynamic studies were conducted to gain insights into the behavior and sorption mechanisms of Cr (VI). The Hill model, a statistical physics model, demonstrated an outstanding fit compared to conventional isotherms. It revealed a saturation adsorption potential of 12.91 mg/g at pH 2, 1.5 g/L dose, and a temperature of 30 °C, corroborating physisorption as the dominant mechanism. XPS results confirmed Cr (VI) reduction to Cr (III) through the appearance of specific peaks at 577.18 and 587.08 eV. Thermodynamic investigations established the endothermicity and spontaneity of the adsorption. In summary, the hematite nanoparticles synthesized in this study exhibit promising potential to remove Cr (VI) from aqueous streams, making them a viable option for water treatment applications.

Silk fibroin-based coating with pH-dependent controlled release of Cu2+ for removal of implant bacterial infections

The implantation of medical devices is frequently accompanied by the invasion of bacteria, which may lead to implant failure. Therefore, an intelligent and responsive coating seems particularly essential in hindering implant-associated infections. Herein, a self-defensive antimicrobial coating, accompanied by silk fibroin as a valve, was successfully prepared on the titanium (Ti-Cu@SF) for pH-controlled release of Cu2+. The results showed that the layer could set free massive Cu2+ to strive against E. coli and S. aureus for self-defense when exposed to a slightly acidic condition. By contrary, a little Cu2+ was released in the physiological situation, which could avoid damage to the normal cells and showed excellent in vitro pH-dependent antibiosis. Besides, in vivo experiment confirmed that Ti-Cu@SF could work as an antibacterial material to kill S. aureus keenly and display negligible toxicity in vivo. Consequently, the design provided support for endowing the layer with outstanding biocompatibility and addressing the issue of bacterial infection during the implantation of Ti substrates.

Quantification of Stern Layer Water Molecules, Total Potentials, and Energy Densities at Fused Silica:Water Interfaces for Adsorbed Alkali Chlorides, CTAB, PFOA, and PFAS

We have employed amplitude- and phase-resolved second-harmonic generation spectroscopy to investigate ion-specific effects of monovalent cations at the fused silica:water interface maintained under acidic, neutral, and alkaline conditions. We find a negligible dependence of the total potential (as negative as -400 mV at pH 14), the second-order nonlinear susceptibility (as large as 1.5 × 10-21 m2 V-1 at pH 14), the number of Stern layer water molecules (1 × 1015 cm-2 at pH 5.8), and the energy associated with water alignment upon going from neutral to high pH (ca. -24 kJ mol-1 to -48 kJ mol-1 at pH 13 and 14, close to the cohesive energy of liquid water but smaller than that of ice) on chlorides of the alkali series (M+ = Li+, Na+, K+, Rb+, and Cs+). Attempts are presented to provide estimates for the molecular hyperpolarizability of the cations and anions in the Stern layer at high pH, which arrive at ca. 20-fold larger values for αtotal ions(2) = αM+(2) + αOH-(2) + αCl-(2) when compared to water's molecular hyperpolarizability estimate from theory and point to a sizable contribution of deprotonated silanol groups at high pH. In contrast to the alkali series, a pronounced dependence of the total potential and the second-order nonlinear susceptibility on monovalent cationic (cetrimonium bromide, CTAB) and anionic (perfluorooctanoic and perfluorooctanesulfonic acid, PFOA and PFOS) surfactants was quantifiable. Our findings are consistent with a low surface coverage of the alkali cations and a high surface coverage of the surfactants. Moreover, they underscore the important contribution of Stern layer water molecules to the total potential and second-order nonlinear susceptibility. Finally, they demonstrate the applicability of heterodyne-detected second-harmonic generation spectroscopy for identifying perfluorinated acids at mineral:water interfaces.

Utilization of biosynthesized silica-supported iron oxide nanocomposites for the adsorptive removal of heavy metal ions from aqueous solutions

This study deals with heavy metal ions removal from simulated water using biosynthesized silica-supported iron oxide nanocomposites (nano-IOS). Agricultural and garden wastes have been utilized to prepare nano-IOS through a green synthesis process. Nano-IOS was characterized by XRD, SEM, FTIR, and zeta potential analysis. The nanocomposites were used to remove five heavy metals, viz., Pb2+, Cd2+, Ni2+, Cu2+, and Zn2+, with optimization of reaction parameters including pH, the concentration of heavy metals, adsorbent dosage, and contact time in batch mode experiments. The optimized dose of nano-IOS was 0.75 g/L for the adsorption of Pb2+, Cd2+, Ni2+, Cu2+, and Zn2+ (10.0 mg/L) with a contact duration of 70 min at pH 5.0 for Pb2+, Cd2+, and Cu2+ and 6.0 for Ni2+ and Zn2+. The adsorption behavior of the nano-adsorbent was well described by Langmuir adsorption isotherm and pseudo-second-order kinetic model indicating chemisorption on the surface of nano-IOS. The adsorption was also found spontaneous and endothermic. Thus, the environmentally benign and bio-synthesized nano-IOS can be utilized as an effective nano-adsorbent for the rapid sequestration of heavy metal ions from water and wastewater.

Remediation and immobilization of Cr(VI)-contaminated soil using stabilized nanoscale iron sulfide and ecological impact

Soil contaminated with hexavalent chromium seriously threatens the environment and human health. The use of FeS, which has a high redox activity and excellent reduction capacity, limits its application in soil remediation due to its premature surface oxidation and massive aggregation. To prevent premature surface oxidation and agglomeration, cetyltrimethylammonium bromide-supported nano-ferrous sulfide (CTAB-nFeS) was chemically synthesized and used for immobilizing Cr(VI) in contaminated soil. In order to evaluate the role of CTAB stabilization of nFeS and interaction mechanisms were investigated by XPS, FTIR, XRD, and FESEM. Batch experiments showed a complete reduction of Cr(VI) within 3 h with only 235% excess of CTAB-nFeS at a soil pH of 8 compared to days as reported in the literature with alternative FeS forms. The reduction kinetic data could be satisfactorily fitted into the second-order rate model. The rate constant linearly depends on the soil-to-water ratio, but its logarithmic form is linear in the given pH range. The oxidation-reduction potential increases with decreasing initial pH, thus positively impacting the reduction process. XPS analysis revealed the reduction process as multi-steps (reduction, adsorption, and co-precipitation). Ecological studies showed improved plant growth and earthworm survival rate in the remediated soil. Medium-term stability experiments suggested a significant decrease in TCLP leachate concentration of Cr after CTAB-nFeS treatment and remained stable for 60 d. Overall results of our study suggested a sustainable, feasible, and effective strategy for in-situ remediation of Cr(VI)-contaminated soil using CTAB-nFeS at natural pH.

Thymol-Loaded Eudragit RS30D Cationic Nanoparticles-Based Hydrogels for Topical Application in Wounds: In Vitro and In Vivo Evaluation

Natural medicines formulated using nanotechnology-based systems are a rich source of new wound-treating therapeutics. This study aims to develop thymol-loaded cationic polymeric nanoparticles (CPNPs) to enhance the skin retention and wound healing efficacy of thymol. The developed materials exhibited entrapment efficiencies of 56.58 to 68.97%, particle sizes of 36.30 to 99.41 nm, and positively charged zeta potential. In Vitro sustained release of thymol up to 24 h was achieved. Selected thymol CPNPs (F5 and C2) were mixed with methylcellulose to form hydrogels (GF5 and GC2). An In Vivo skin-retention study revealed that GF5 and GC2 showed 3.3- and 3.6-fold higher retention than free thymol, respectively. An In Vitro scratch-wound healing assay revealed a significant acceleration in wound closure at 24 h by 58.09% (GF5) and 57.45% (GC2). The potential for free thymol hydrogel, GF5, and GC2 to combat MRSA in a murine skin model was evaluated. The bacterial counts, recovered from skin lesions and the spleen, were assessed. Although a significant reduction in the bacterial counts recovered from the skin lesions was shown by all three formulations, only GF5 and GC2 were able to reduce the bacterial dissemination to the spleen. Thus, our study suggests that Eudragit RS30D nanoparticles-based hydrogels are a potential delivery system for enhancing thymol skin retention and wound healing activity.

Progress toward Room-Temperature Synthesis and Functionalization of Iron-Oxide Nanoparticles

Novel magnetic nanohybrids composed of nanomaghemite covered by organic molecules were successfully synthesized at room temperature with different functionalization agents (sodium polystyrene sulfonate, oxalic acid, and cetyltrimethylammonium bromide) in low and high concentrations. Structural, vibrational, morphological, electron energy-loss spectroscopy, magnetic, and Mössbauer characterizations unraveled the presence of mainly cubic inverse spinel maghemite (γ-Fe₂O₃), whilst X-ray diffraction and ⁵⁷Fe Mössbauer spectroscopy showed that most samples contain a minor amount of goethite phase (α-FeOOH). Raman analysis at different laser power revealed a threshold value of 0.83 mW for all samples, for which the γ-Fe₂O₃ to α-Fe₂O₃ phase transition was observed. Imaging microscopy revealed controlled-size morphologies of nanoparticles, with sizes in the range from 8 to 12 nm. Organic functionalization of the magnetic nanoparticles was demonstrated by vibrational and thermogravimetric measurements. For some samples, Raman, magnetic, and Mössbauer measurements suggested an even more complex core-shell-like configuration, with a thin shell containing magnetite (Fe₃O₄) covering the γ-Fe₂O₃ surface, thus causing an increase in the saturation magnetization of approximately 11% against nanomaghemite. Field cooling hysteresis curves at 5 K did not evidence an exchange bias effect, confirming that the goethite phase is not directly interacting magnetically with the functionalized maghemite nanoparticles. These magnetic nanohybrids may be suitable for applications in effluent remediation and biomedicine.

Effect of different molecular coatings on the heating properties of maghemite nanoparticles

In this work, the effect of different molecular coatings on the alternating magnetic field-induced heating properties of 15 nm maghemite nanoparticles (NPs) in water dispersions was studied at different frequencies (159-782 kHz) and field amplitudes (100-400 G). The original hydrophobic oleate coating was replaced with dimercaptosuccinic acid (DMSA) or polyethylene glycol trimethoxysilane (PEGTMS), while cetrimonium bromide (CTAB) or stearic acid-poloxamer 188 (SA-P188) was intercalated or encapsulated, respectively, to transfer the dispersions into water. Surface modification, based on intercalation processes, induced clustering phenomena with the formation of spherical-like assemblies (CTAB and SA-P188), while ligand-exchange strategies kept the particles isolated. The clustering phenomenon has detrimental effects on the heating performances compared with isolated systems, in line with the reduction of Brown relaxation times. Furthermore, broader comprehension of the heating phenomenon in this dynamic system is obtained by following the evolution of SPA and ILP with time and temperature beyond the initial stage.

Pharmaceuticals removal by synergistic adsorption and S-scheme photocatalysis using nano-CeO2-coupled Fe3O4 on a CTAB matrix and investigation of the nanocomposite's antibacterial and antibiofilm activities: intrinsic degradation mechanism

S-Scheme photocatalytic mechanism of a fabricated nano-heterojunction.

Feasibility of magnetic nano adsorbent impregnated with activated carbon from animal bone waste: Application for the chromium (VI) removal

Chromium is the heavy metal which existing in the effluents cause extensive discomfort to the environmental components. Bone waste is widely generated in food processing industries and restaurants. It is now used by switching into activated carbon. By co-precipitation procedure, the activated carbon is coated with a nano adsorbent. The Fe₃O₄-BAC adsorbent potential was established in this study via several batch tests. The adsorbing adverts had super magnetic behavior, and the magnetization value was 22 emu/g. The SEM imaging of the Fe₃O₄-BAC shows an improved morphology of 100-446 nm, and the nanoparticles were monodispersed. The present investigation also delves into the study of system parameters on the removal of metal ions. Optimal adsorption has been found at the acidic pH at the contact time of 60min for the adsorbent amount of 5 g/L. Maximum capacity of adsorption by nano adsorbent was 27.86 mg/g. Thermodynamic and isotherm tests have established the process viability. In addition, the kinetic studies establish the inclination of the studied Fe₃O₄-BAC towards pseudo-first order models. Hence, Fe₃O₄-BAC could be potential adsorbent to remove chromium from an aqueous solution.

Heavy Metal Adsorption Using Magnetic Nanoparticles for Water Purification: A Critical Review

Research on contamination of groundwater and drinking water is of major importance. Due to the rapid and significant progress in the last decade in nanotechnology and its potential applications to water purification, such as adsorption of heavy metal ion from contaminated water, a wide number of articles have been published. An evaluating frame of the main findings of recent research on heavy metal removal using magnetic nanoparticles, with emphasis on water quality and method applicability, is presented. A large number of articles have been studied with a focus on the synthesis and characterization procedures for bare and modified magnetic nanoparticles as well as on their adsorption capacity and the corresponding desorption process of the methods are presented. The present review analysis shows that the experimental procedures demonstrate high adsorption capacity for pollutants from aquatic solutions. Moreover, reuse of the employed nanoparticles up to five times leads to an efficiency up to 90%. We must mention also that in some rare occasions, nanoparticles have been reused up to 22 times.

Development of functional lignin-based spherical particles for the removal of vanadium(V) from an aqueous system

A new type of functional lignin-based spherical particles (L-CTAB) prepared with the use of hexadecyltrimethylammonium bromide (CTAB) was applied as an effective biosorbent for removing vanadium(V) ions. The porous structure, characteristic functional groups, electrokinetic stability, morphology and size of the L-CTAB particles were examined. The conditions of removal were also investigated, including pH (2-12), sorbent mass (0.1-0.5 g), concentration (10-100 mg/dm3), phase contact time (1-240 min) and temperature (293-333 K). At pH 5.0 the maximum sorption percentage (%S) of V(V) was 45%, while at pH 2.0 it was 32%. The maximum sorption capacity of V(V) for L-CTAB was found to be 10.79 mg/g. The kinetic data indicate that the sorption followed the pseudo-second-order and film diffusion models. Sorption equilibrium for V(V) ions removal by L-CTAB was reached after 60 min at the initial concentrations 10 and 50 mg/dm³. It has been shown that the adsorption of V(V) ions on the surface of L-CTAB is a heterogeneous, endothermic and spontaneous reaction, as evidenced by the calculated values of thermodynamic parameters - free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) - for the tested systems at different temperatures. HCl solutions, used as an L-CTAB regeneration agent, quantitatively eluted V(V) ions.

Immunosensor Based on Zinc Oxide Nanocrystals Decorated with Copper for the Electrochemical Detection of Human Salivary Alpha-Amylase

(1) Background: Nanocrystals (NCs)-based electrochemical sensors have been proposed for biomarkers detection, although immunosensors using ZnO NCs decorated with copper are still scarce. (2) Methods: Electrochemical immunodetection of human salivary alpha-amylase (HSA) used ZnO, CuO, and ZnO:xCu (x = 0.1, 0.4, 1.0, 4.0, and 12.0) NCs. (3) Results: Substitutional incorporation of Cu2+ in the crystalline structure of ZnO and formation of nanocomposite were demonstrated by characterization. Graphite electrodes were used and the electrochemical signal increased by 40% when using ZnO:1Cu and 4Cu (0.25 mg·mL-1), in an immunosensor (0.372 mg·mL-1 of anti-alpha-amylase and 1% of casein). Different interactions of HSA with the alpha-amylase antibody were registered when adding the NCs together, either before or after the addition of saliva (4 μL). The immunosensor changed specificity due to the interaction of copper. The ZnO:1Cu and ZnO:4Cu samples showed 50% interference in detection when used before the addition of saliva. The immunosensor showed 100% specificity and a sensitivity of 0.00196 U·mL-1. (4) Conclusions: Results showed that the order of NCs addition in the sensors should be tested and evaluated to avoid misinterpretation in detection and to enable advances in the validation of the immunosensor.

Investigation the Effects of Green-Synthesized Copper Nanoparticles on the Performance of Activated Carbon-Chitosan-Alginate for the Removal of Cr(VI) from Aqueous Solution

In the present investigation, green nano-zerovalent copper (GnZVCu), activated carbon (AC), chitosan (CS) and alginate (ALG) nanocomposites were produced and used for the elimination of chromium (VI) from a polluted solution. The nanocomposites GnZVCu/AC-CS-alginate and AC-CS-alginate were prepared. Analysis and characterization were performed by the following techniques: X-ray diffraction, energy dispersive X-ray spectroscopy, scanning electron microscopy, transmission electron microscopy and Fourier transform infrared spectroscopy. The SEM analysis revealed that the nanocomposites are extremely mesoporous, which leads to the greatest adsorption of Cr+6 (i.e., 97.5% and 95%) for GnZVCu/AC-CS-alginate and AC-CS-alginate, respectively. The adsorption efficiency was enhanced by coupling GnZVCu with AC-CS-alginate with a contact time of 40 min. The maximum elimination of Cr+6 with the two nanocomposites was achieved at pH 2. The isotherm model, Freundlich adsorption isotherm and kinetics model and P.S.O.R kinetic models were discovered to be better suited to describe the exclusion of Cr+6 by the nanocomposites. The results suggested that the synthesized nanocomposites are promising for the segregation of Cr+6 from polluted solutions, specially the GnZVCu/AC-CS-alginate nanocomposite.

Surface treated acid-activated carbon for adsorption of anionic azo dyes from single and binary adsorptive systems: A detail insight

Current study deals with the surface modification of acid activated carbon (prepared from Pongamia pinnata shells) with Cetyltrimethylammonium bromide (CTAB) and its role as an adsorbent in eliminating anionic azo dyes viz. Congo red (CR) and Direct blue 6 (DB) from single and binary adsorptive systems. Binary adsorptive system involved the synergistic and antagonistic influence of one dye over the adsorption of other dye. Physico-chemical alterations due to surfactant modification and post adsorption were studied using atomic force microscopy (AFM), Zeta Potential, scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDS), surface area analysis and Fourier-transformed infrared spectroscopy (FTIR). Process parameters influencing efficient adsorption of CR and DB species viz. initial pH of dye solution, adsorbent dosage, incubation temperature and initial concentration of dye species were optimised. Sorbate-sorbent interaction studies for single adsorptive system revealed sorbate's monolayer formation over adsorbent's surface and the involvement of chemisorption, as verified by Langmuir isotherm model and pseudo-second order model, respectively. Langmuir maximum adsorption capacity of the adsorbent was 555.56 mg/g for CR and 625.00 mg/g for DB. Meanwhile, for binary adsorptive system, competitive Langmuir model verified both CR and DB had antagonistic/competitive effect over each other's adsorption. Thermodynamic analysis revealed the adsorptive process as exothermic, spontaneous and thermodynamically favourable with an elevated degree of dis-orderedness. Co-existing cations and anions has nominal effect on the adsorption capacity of dyes. Recyclability studies verified a modest efficiency of 62.52% for CR and 50.47% for DB species after the end of 4th adsorption-desorption cycle; thus affirming its recyclability potential. Phytotoxic assay affirmed the effectivity of the adsorbent in adsorbing dye species from aqueous solutions using Vigna mungo seeds as the model.

Assessing magnetic and inductive thermal properties of various surfactants functionalised Fe3O4 nanoparticles for hyperthermia

This work reports the fabrication of magnetite (Fe₃O₄) nanoparticles (NPs) coated with various biocompatible surfactants such as glutamic acid (GA), citric acid (CA), polyethylene glycol (PEG), polyvinylpyrrolidine (PVP), ethylene diamine (EDA) and cetyl-trimethyl ammonium bromide (CTAB) via co-precipitation method and their comparative inductive heating ability for hyperthermia (HT) applications. X-ray and electron diffraction analyses validated the formation of well crystallined inverse spinel structured Fe₃O₄ NPs (crystallite size of ~ 8–10 nm). Magnetic studies confirmed the superparamagnetic (SPM) behaviour for all the NPs with substantial magnetisation (63–68 emu/g) and enhanced magnetic susceptibility is attributed to the greater number of occupations of Fe²⁺ ions in the lattice as revealed by X-ray photoelectron spectroscopy (XPS). Moreover, distinctive heating response (specific absorption rate, SAR from 130 to 44 W/g) of NPs with similar size and magnetisation is observed. The present study was successful in establishing a direct correlation between relaxation time (~ 9.42–15.92 ns) and heating efficiency of each surface functionalised NPs. Moreover, heat dissipated in different surface grafted NPs is found to be dependent on magnetic susceptibility, magnetic anisotropy and magnetic relaxation time. These results open very promising avenues to design surface functionalised magnetite NPs for effective HT applications.

A review: a comparison of different adsorbents for removal of Cr (VI), Cd (II) and Ni (II)

A review of the studies dealing with the removal of chromium, cadmium, and nickel ions with different adsorbents published in the literature between 2014 and 2018 is given in tabular form, along with the adsorption conditions, adsorption isotherm, and kinetic models applied by the authors to model the experimental data and adsorption capacities. The review focuses on the efficiency of ion removal.

The role of kaolin and kaolin/ZnO nanoadsorbents in adsorption studies for tannery wastewater treatment

In the present study, comparative studies of kaolin and kaolin/ZnO nanocomposites for the adsorption of Cr(VI), Fe(III), COD, BOD, and chloride from tannery wastewater were investigated. ZnO nanoparticles and kaolin/ZnO nanocomposites were prepared by sol-gel followed by wet-impregnation methods. The prepared adsorbents were characterized using different analytical tools such as X-ray diffraction, Fourier transforms infrared, high-resolution transmission electron microscopy, energy dispersive spectroscopy, selective area electron diffraction and Brunauer Emmett-Teller (BET) and X-ray Photoelectron Spectroscopy (XPS). The HRSEM/EDS/XPS analysis confirmed successful immobilization of clay structural network on the lattice layers of zincite hexagonal structure of ZnO nanoparticles. BET measurement showed an increase in the surface area of kaolin/ZnO nanocomposites (31.8 m²/g) when compared to kaolin (17 m²/g). Batch adsorption studies were carried out by varying the parameters such as contact time, adsorbent dosage and temperature. The maximum removal of Cr(VI) (100%), Fe(III) (98%), COD (95%), BOD (94%) and Chloride (78%) was obtained at 15 min by kaolin/ZnO composites. While 78% Cr(VI), 91% Fe(III), 91% COD, 89% BOD and 73% Chloride were removed by kaolin under the same conditions. The kaolin/ZnO nanocomposites exhibited better adsorption performance than kaolin due to higher surface area of the former than the latter. It was found that the Jovanovic isotherm model fitted the adsorption experimental data most with the highest correlation (R² > 0.99) for both nanoadsorbents and indicate the occurrence of adsorption on monolayer and heterogeneous surfaces. The mechanism for the adsorption of metal ions in tannery wastewater onto the nano-adsorbents was examined using Weber Morris intra-particle diffusion model and Boyd plot which showed that the adsorption process was both intra-particle and film diffusion controlled. The thermodynamic parameters such as enthalpy change showed that that adsorption of metal ions and other parameters was feasible, spontaneous and endothermic. The ZnO/clay nanocomposites exhibited excellent recyclable and re-useable properties even after six repeated applications and can, therefore, be applied in wastewater treatment for removal of heavy metals and other physicochemical parameters.

Removal and Oxidation of As(III) from Water Using Iron Oxide Coated CTAB as Adsorbent

Iron oxides such as magnetite and maghemite coated with cetyltrimethylammonium bromide (CTAB) are very promising materials for wastewater treatment because iron oxide can be easily separated from solutions using the magnetic separation procedure Iron oxide (IO) coated CTAB was synthesized by an adapted co-precipitation method. In the present study, the IO-CTAB was used for removing arsenic from water for the first time. In the present study, the performance of iron oxide coated CTAB biocomposites as an adsorbent for arsenic removal from aqueous solutions was examined. X-ray diffraction (XRD) analysis and the results revealed a cubic phase Fd-3 m of Fe₃O₄ with lattice a = 8.40 Å and average crystal size equal to 17.26 ± 3 nm. The mean particle size calculated from transmission electron microscopy (TEM) was 19.86 ±1.7 nm. The results of the adsorption batch experiments and the data determined using the Langmuir and Freundlich models emphasized that IO-CTAB nanoparticles were favorable for the adsorption of As(III) ions from aqueous solutions. Ultrasound measurements have shown that IO-CTAB is a cost-effective biocomposite for removing arsenic from contaminated solutions. Moreover, x-ray photoelectron spectroscopy (XPS) has shown that during the process of arsenic absorption, there is oxidation from As(III) to As(V), which leads to a decrease in toxicity during this process. The results of the cytotoxic assays confirmed that the IO-CTAB nanoparticles did not induce any morphological changes in the HeLa cells and did not affect their proliferation after 24 h of incubation.

Preparation of Long-Term Antibacterial SiO2-Cinnamaldehyde Microcapsule via Sol-Gel Approach as a Functional Additive for PBAT Film

The mesoporous silica wall materials can achieve controlled load and sustained-release of active agents. An antimicrobial nanoscale silica microcapsule containing cinnamaldehyde (CA) was prepared by the sol-gel method and applied in poly (butyleneadipate-co-terephthalate) (PBAT) film. The surface morphology, physical and chemical properties, and antibacterial properties of microcapsules and films were studied. The effects of different temperatures and humidities on the release behavior of microcapsules were also evaluated. Results showed that CA was successfully encapsulated in silica microcapsule which had a diameter of 450–700 nm. The antibacterial CA agent had a long-lasting release time under lower temperature and relative humidity (RH) environment. At low temperature (4 °C), the microcapsules released CA 32.35% in the first 18 h, and then slowly released to 56.08% in 216 h; however, the microcapsules released more than 70% in 18 h at 40 °C. At low humidity (50%RH), the release rates of microcapsules at the 18th h and 9th d were 43.04% and 78.01%, respectively, while it reached to equilibrium state at 72 h under 90% RH. The sustained release process of CA in SiO2-CA microcapsules follows a first-order kinetic model. Physicochemical properties of PBAT films loaded with different amounts of microcapsules were also characterized. Results showed that the tensile strength and water vapor transmission rate (WVTR) of the composite film containing 2.5% microcapsules were increased by 26.98% and 14.61%, respectively, compared to the raw film, while the light transmittance was slightly reduced. The crystallinity of the film was improved and can be kept stable up to 384.1 °C. Furthermore, microcapsules and composite film both exhibited distinctive antibacterial effect on Escherichia coli and Listeria monocytogenes. Therefore, SiO2-CA microcapsules and composite films could be a promising material for the active packaging.

Lignin-Based Spherical Structures and Their Use for Improvement of Cilazapril Stability in Solid State

Biopolymer-based spherical particles exhibit unique properties including narrow sizes and many functional groups on their surfaces. Therefore, they show great potential for application in many scientific and industrial processes. The main aim of this study was to prepare lignin-based spherical particles with the use of a cationic surfactant, hexadecyl(trimethyl)ammonium bromide (CTAB). In the first step, different preparation procedures were tested with varying parameters, including biopolymer and surfactant ratios, lignin filtration, and experimental time. The morphological and dispersion characteristics of the materials were determined to select the best samples with the most promising properties, which could then be tested for their acute toxicity. It was observed that almost all materials were characterized by spherical shapes in micro- and nanosizes. The sample with the best physicochemical properties was used for further analysis and then tested for medical applications: the improvement of the stability of a drug molecule, cilazapril (CIL). The formulated material (CIL@LC-2a 1:1 wt./wt.) exhibited outstanding properties and significantly improved the stability of cilazapril as tested in conditions of increased temperature and humidity. Lignin spherical particles may be employed as a promising material for shielding other active compounds from decomposition.

Investigating the Properties of Cetyltrimethylammonium Bromide/Hydroxylated Graphene Quantum Dots Thin Film for Potential Optical Detection of Heavy Metal Ions

The modification of graphene quantum dots (GQDs) may drastically enhance their properties, therefore resulting in various related applications. This paper reported the preparation of novel cetyltrimethylammonium bromide/hydroxylated graphene quantum dots (CTAB/HGQDs) thin film using the spin coating technique. The properties of the thin film were then investigated and studied. The functional groups existing in CTAB/HGQDs thin film were confirmed by the Fourier transform infrared (FTIR) spectroscopy, while the atomic force microscope (AFM) displayed a homogenous surface of the thin film with an increase in surface roughness upon modification. Optical characterizations using UV-Vis absorption spectroscopy revealed a high absorption with an optical band gap of 4.162 eV. Additionally, the photoluminescence (PL) spectra illustrated the maximum emission peak of CTAB/HGQDs thin film at a wavelength of 444 nm. The sensing properties of the as-prepared CTAB/HGQDs thin film were studied using a surface plasmon resonance technique towards the detection of several heavy metal ions (HMIs) (Zn2+, Ni2+, and Fe3+). This technique generated significant results and showed that CTAB/HGQDs thin film has great potential for HMIs detection.

The Sorption Performance of Cetyl Trimethyl Ammonium Bromide-Capped La0.9Sr0.1FeO3 Perovskite for Organic Pollutants from Industrial Processes

La_0.9Sr_0.1FeO₃ perovskite, prepared by the microwave-assisted method, was capped with cetyl trimethyl ammonium bromide (CTAB) cationic surfactant, and applied as a sorbent for the removal of the anionic Congo red (CR) dye from aqueous solutions. X-ray diffraction (XRD) patterns showed that the perovskite structure was not affected by capping; however, the particle size increased. There was a hipsochromic shift in the value of λ_max of the CR absorption spectrum in the presence of CTAB, which indicated the formation of an oppositely charged dye–surfactant complex. The adsorption efficiency of CTAB-capped La_0.9Sr_0.1FeO₃ was independent of the pH of the solution—equilibrium was reached after a few minutes. The value of the maximum adsorption capacity, q_m, was 151.52 mg·g⁻¹, which was 10-times higher than that of the pure perovskite. The proposed sorbent maintained its excellent sorption ability in the presence of the sample matrix; therefore, it can be regenerated and reused with unchanged performance.

Influence of Magnetic Nanoparticles on Modified Polypyrrole/m-Phenylediamine for Adsorption of Cr(VI) from Aqueous Solution

A novel, modified polypyrrole/m-phenylediamine (PPy-mPD) composite, decorated with magnetite (Fe3O4) nanoparticles, and prepared via an in-situ oxidative polymerisation, was investigated. The PPy-mPD/Fe3O4 nanocomposite was employed for the removal of highly toxic oxyanion hexavalent chromium Cr(VI) from an aqueous solution. The structure and successful formation of the PPy-mPD/Fe3O4 nanocomposite was confirmed and investigated using various techniques. The presence of Fe3O4 was confirmed by high resolution transmission electron microscopy, with an appearance of Fe lattice fringes. The estimation of the saturation magnetisation of the nanocomposite, using a vibrating sample magnetometer, was observed to be 6.6 emu/g. In batch adsorption experiments, PPy-mPD/Fe3O4 nanocomposite (25 mg) was able to remove 99.6% of 100 mg/L of Cr(VI) at pH 2 and 25 °C. Adsorption isotherms were investigated at different Cr(VI) concentration (100-600 mg/L) and temperature (15-45 °C). It was deduced that adsorption follows the Langmuir model, with a maximum adsorption capacity of 555.6 mg/g for Cr(VI) removal. Furthermore, isotherm data were used to calculate thermodynamic values for Gibbs free energy, enthalpy change and entropy change, which indicated that Cr(VI) adsorption was spontaneous and endothermic in nature. Adsorption-desorption experiments revealed that the nanocomposite was usable for two consecutive cycles with no significant loss of adsorption capacity. This research demonstrates the application potential for the fascinating properties of PPy-mPD/Fe3O4 nanocomposite as a highly efficient adsorbent for the removal of heavy metal ions from industrial wastewater.

Response surface methodology based on central composite design for simultaneous adsorption of rare earth elements using nanoporous calcium alginate/carboxymethyl chitosan microbiocomposite powder containing Ni0.2Zn0.2Fe2.6O4 magnetic nanoparticles: Batch and column studies

In this research paper, the utilization of the magnetic calcium alginate/carboxymethyl chitosan/Ni_0.2Zn_0.2Fe_2.6O₄ (CA/CMC/Ni_0.2Zn_0.2Fe_2.6O₄) was investigated for the simultaneous aqueous adsorption of Nd (III), Tb (III), and Dy (III). The magnetic products were characterized by FE-SEM, EDX, XRD, FT-IR, TGA, and VSM techniques. The saturation magnetization value for Ni_0.2Zn_0.2Fe_2.6O₄ and CA/CMC/Ni_0.2Zn_0.2Fe_2.6O₄ was found to be 45.87 and 14.14 emu/g, respectively. Using RSM, a quadratic polynomial equation was obtained to predict the adsorption efficiency of each ion. Under the conditions of pH = 5.5, adsorbent dosage of 0.1 g, initial concentration of 30 mg/L, and contact time of 53 min predicted by RSM, the adsorption efficiencies of Nd (III), Tb (III), and Dy (III) were respectively 95.72, 96.17, and 99.44%. The isotherm and kinetic data were respectively fitted well with Freundlich and pseudo-second-order (PSO) models. The desorption of the loaded ions was effectively carried out by 0.2 M HNO₃, and the adsorbent was consecutively utilized with 2.54, 1.63, and 1.16% decrease in adsorption efficiency for Nd (III), Tb (III), and Dy (III), respectively, after the forth cycle. Additionally, the adsorption behavior of the CA/CMC/Ni_0.2Zn_0.2Fe_2.6O₄ towards Nd (III), Tb (III), and Dy (III) was studied by using a fixed-bed column technique.

Hazardous heavy metals contamination of vegetables and food chain: Role of sustainable remediation approaches - A review

This review emphasizes the role of toxic metal remediation approaches due to their broad sustainability and applicability. The rapid developmental processes can incorporate a large quantity of hazardous and unseen heavy metals in all the segments of the environment, including soil, water, air and plants. The released hazardous heavy metals (HHMs) entered into the food chain and biomagnified into living beings via food and vegetable consumption and originate potentially health-threatening effects. The physical and chemical remediation approaches are restricted and localized and, mainly applied to wastewater and soils and not the plant. The nanotechnological, biotechnological and genetical approaches required to more rectification and sustainability. A cellular, molecular and nano-level understanding of the pathways and reactions are responsible for potentially toxic metals (TMs) accumulation. These approaches can enable the development of crop varieties with highly reduced concentrations of TMs in their consumable foods and vegetables. As a critical analysis by authors observed that nanoparticles could provide very high adaptability for both in-situ and ex-situ remediation of hazardous heavy metals (HHMs) in the environment. These methods could be used for the improvement of the inbuilt genetic potential and phytoremediation ability of plants by developing transgenic. These biological processes involve the transfer of gene of interest, which plays a role in hazardous metal uptake, transport, stabilization, inactivation and accumulation to increased host tolerance. This review identified that use of nanoremediation and combined biotechnological and, transgenic could help to enhance phytoremediation efficiency in a sustainable way.