Adsorption and photodegradation of organic contaminants by silver nanoparticles: isotherms, kinetics, and computational analysis.

In view of the widespread and distribution of several classes and types of organic contaminants, increased efforts are needed to reduce their spread and subsequent environmental contamination. Although several remediation approaches are available, adsorption and photodegradation technologies are presented in this review as one of the best options because of their environmental friendliness, cost-effectiveness, accessibility, less selectivity, and wider scope of applications among others. The bandgap, particle size, surface area, electrical properties, thermal stability, reusability, chemical stability, and other properties of silver nanoparticles (AgNPS) are highlighted to account for their suitability in adsorption and photocatalytic applications, concerning organic contaminants. Literatures have been reviewed on the application of various AgNPS as adsorbent and photocatalyst in the remediation of several classes of organic contaminants. Theories of adsorption have also been outlined while photocatalysis is seen to have adsorption as the initial mechanism. Challenges facing the application of silver nanoparticles have also been highlighted and possible solutions have been presented. However, current information is dominated by applications on dyes and the view of the authors supports the need to strengthen the usefulness of AgNPS in adsorption and photodegradation of more classes of organic contaminants, especially emerging contaminants. We also encourage the simultaneous applications of adsorption and photodegradation to completely convert toxic wastes to harmless forms.

Zinc oxide nanoparticles adsorb emerging pollutants (glyphosate pesticide) from aqueous solutions.

The present study captures the precipitation synthesis of zinc nanoparticles and modification with alumina and oleic acid. The crystalline size evaluated from the XRD profile of the zinc oxide nanoparticles was 18.05 nm but was reduced to 14.20 and 14.50 nm upon modification with oleic acid and alumina. The XRD spectra also showed evidence of the amorphous nature of zinc oxide nanoparticles and subsequent enhancement upon modification. A porous appearance was observed in the SEM instrumentation but seems to be enhanced by modification. The FTIR absorption spectra of the nanoparticles showed a peak associated with ZnO vibration around 449 cm, but the enhanced intensity was observed due to modification. The prepared ZnO-NPs and the modified samples were good materials for the adsorption removal of glyphosate from water, recording efficiencies above 94% at neutral pH and showing a possible incremental trend with an enhanced period of contact and adsorbent dosage. The adsorbents showed maximum capacity that ranged from 82.85 to 82. 97 mg/g. The adsorption models of Freundlich, Temkin, Dubinin-Radushkevich and BET showed excellent fitness. Results from computational results complemented experimental data and were used to identify the sites for adsorption and characteristics of molecular descriptors for the systems.

Synthesis and application of novel microporous framework of nanocomposite from trona for photocatalysed degradation of methyl orange dye.

Photocatalysed degradation of environmental contaminants is one of the most fashionable technologies in the purification of water because the method converts toxic products to nontoxic ones. In this study, a method has been developed to synthesize novel nanocomposites of Na-Ca-Al-Si oxides for the first time. The average surface area, pore volume and pore size for the novel product were 1742.55 m2/g, 0.3499 cc/g and 3.197 nm respectively. The crystal parameters were a = 7.1580 Å, b = 7.4520 Å, c = 7.7160 Å, α = 115.0600, ß = 107.3220, γ = 100.4380, density (calculated) = 2.0 × 103g/cm3 and cell volume = 332.7 Å3 respectively. The average crystalline size deduced from the Scherrer equation (i.e. 6.9393 nm) was higher than the value of 1.024 nm obtained from the graphical method. The FTIR and UV spectra of the nanocomposites were unique and provided baseline information that characterises the new product. XRD profiling of the new product reveals the existent of a silica framework consisting of NaAlSi3O3 and CaAl2Si2O8 The synthesized nanocomposites is an effective photocatalyst for the degradation of methyl orange dye in water, with aoptimum efficiency of 96% at an initial dye concentration of 10 ppm, the adsorbent dosage of 0.5 g,contact time of 90 min and pH of 2.5. The Langmuir-Hinshelwood, modified Freundlich and pseudo-second kinetic models were significant in the description of the photocatalytic kinetics of the degraded dye molecules.

A Brief Review on Fruit and Vegetable Extracts as Corrosion Inhibitors in Acidic Environments.

The corrosion of metals, i.e., the initiation and acceleration of the surface deterioration of metals through an electrochemical reaction with the surrounding intrusive environment, is a global concern because of the economic and environmental impacts. Corrosion inhibitors are considered the most practical choice among the available corrosion protection techniques due to their effectiveness in terms of functionality and cost. The use of traditional and toxic corrosion inhibitors has led to environmental issues, arousing the need for green counterparts that are environmentally friendly, easily accessible, biodegradable, and cost-effective. In this review, the utilization of green corrosion inhibitors purely acquired from renewable sources is explored, with an in-depth focus on the recent advancements in the use of fruit and vegetable extracts as green corrosion inhibitors. In particular, fruits and vegetables are natural sources of various phytochemicals that exhibit key potential in corrosion inhibition. To shed light on the true potential of such extracts in the protection of steel in acidic environments, the experimental techniques involved in corrosion inhibition and the mechanism of corrosion inhibition are discussed in detail. The study highlights the potential of fruit and vegetable extracts as non-toxic, economical, and effective corrosion inhibitors in the pursuit of green chemistry. In addition to discussing and outlining the current status and opportunities for employing fruit and vegetable extracts as corrosion inhibitors, the current review outlines the challenges involved in the utilization of such extracts in corrosion inhibition.

Influence of pozzolanic addition on strength and microstructure of metakaolin-based concrete.

The intent of this study is to explore the physical properties and long-term performance of concrete made with metakaolin (MK) as a binder, using microsilica (MS) and nanosilica (NS) as substitutes for a portion of the ordinary Portland cement (OPC) content. The dosage of MS was varied from 5% to 15% for OPC-MK-MS blends, and the dosage of NS was varied from 0.5% to 1.5% for OPC-MK-NS blends. Incorporation of these pozzolans accelerated the hardening process and reduced the flowability, consistency, and setting time of the cement paste. In addition, it produced a denser matrix, improving the strength of the concrete matrix, as confirmed by scanning electron microscopy and X-ray diffraction analysis. The use of MS enhanced the strength by 10.37%, and the utilization of NS increased the strength by 11.48% at 28 days. It also reduced the penetrability of the matrix with a maximum reduction in the water absorption (35.82%) and improved the resistance to the sulfate attack for specimens containing 1% NS in the presence of 10% MK. Based on these results, NS in the presence of MK can be used to obtain cementitious structures with the enhanced strength and durability.

Enhanced Zn(II) adsorption by chemically modified sawdust based biosorbents.

Heavy metals present in industrial effluents, when discharged into water channels, not only affect humans but also negatively impact plants and aquatic organisms. Sawdust is available readily in developing countries and can be used by small-scale industries for effluent water treatment containing low concentrations of bivalent zinc ions. This study explores the potential of sawdust-derived biosorbents, after boiling (SDB), chemical modification with formaldehyde (SDF), and sulfuric acid (SDS), for sequestration of Zn(II) from simulated wastewater as well as industrial effluents. The morphological analysis of the three biosorbents indicated a suitable porous structure with a pore size of 232.928 m2/g (SDB), 291.102 m2/g (SDF), and 498.873 m2/g (SDS). The functional analysis of native and metal-laden biosorbents indicated the role of - OH, - C = O, and - NH functional groups in Zn(II) binding. The process parameters were optimized and the spontaneous adsorption of Zn(II) was found to proceed by multilayer formation by following pseudo-second-order kinetics. SDS adsorbent (0.1 g) exhibited a greater potential for removal of Zn(II) from industrial effluents as compared to SDB and SDF at pH = 6.0 with the equilibrium adsorption capacity of 45.87 mg/g. Therefore, SDS could be a promising adsorbent for the treatment of wastewater in small-scale industries.

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.

Rapid adsorptive removal of chromium from wastewater using walnut-derived biosorbents.

Contamination of water resources by industrial effluents containing heavy metal ions and management of solid waste from agricultural and food industries is a serious issue. This study presents the valorization of waste walnut shells as an effective and environment-friendly biosorbent for sequestrating Cr(VI) from aqueous media. The native walnut shell powder (NWP) was chemically modified with alkali (AWP) and citric acid (CWP) to obtain modified biosorbents with abundant availability of pores as active centers, as confirmed by BET analysis. During batch adsorption studies, the process parameters for Cr(VI) adsorption were optimized at pH 2.0. The adsorption data were fitted to isotherm and kinetic models to compute various adsorption parameters. The adsorption pattern of Cr(VI) was well explained by the Langmuir model suggesting the adsorbate monolayer formation on the surface of the biosorbents. The maximum adsorption capacity, qm, for Cr(VI) was achieved for CWP (75.26 mg/g), followed by AWP (69.56 mg/g) and NWP (64.82 mg/g). Treatment with sodium hydroxide and citric acid improved the adsorption efficiency of the biosorbent by 4.5 and 8.2%, respectively. The endothermic and spontaneous adsorption was observed to trail the pseudo-second-order kinetics under optimized process parameters. Thus, the chemically modified walnut shell powder can be an eco-friendly adsorbent for Cr(VI) from aqueous solutions.

Theoretical and experimental studies on photocatalytic removal of methylene blue (MetB) from aqueous solution using oyster shell synthesized CaO nanoparticles (CaONP-O).

The development of technologies for the removal of dye from aqueous solution is most desirable if the end product is relatively green (i.e., environmentally friendly). Photodegradation (as one of such technology) and photolysis (without the catalyst) was applied to investigate the role of sol-gel synthesized calcium oxide nanoparticle (using the oyster shell as the precursor). The results obtained gave substantial evidence that calcium oxide nanoparticles catalyzed the degradation of the methylene blue dye up to a maximum percentage of 98 % removal. Degradation efficiency displayed a strong dependency on time, initial dye concentration, catalyst load, pH, and ionic strength. Chi-square and sum of square error analysis indicated that the photodegradation kinetics fitted the Langmuir-Hinshelwood, first order, and pseudo first-order models best. The half-life of the dye was significantly reduced from hours to minutes due to photocatalysis. Quantum chemical calculations indicated that the degradation proceeded through adsorption, deformation/degradation, and desorption through the chloride end of the molecule linked to the calcium active center of the catalyst. Results from Fukui functions and molecular descriptors analysis confirmed the mechanism of photocatalysis.

Quantum and experimental investigation of the application of Crassostrea gasar (mangrove oyster) shell-based CaO nanoparticles as adsorbent and photocatalyst for the removal of procaine penicillin from aqueous solution.

The present study was designed to synthesize and characterize calcium oxide nanoparticles (using mangrove oyster shell as a precursor) and apply the synthesized nanoparticles as a photocatalyst to degrade procaine penicillin in an aqueous solution. The photocatalyst exhibited an average band gap of 4.42 eV, showed a maximum wavelength of absorbance in the UV region (i.e., 280 nm), and is a microporous nanoparticle with a particle diameter of 50 nm. The photocatalyzed degradation of the drug was conducted under natural sunlight, and the influence of parameters such as the period of contact, catalyst load, pH, initial drug concentration, and ionic strength was investigated concerning the degradation profile. The results obtained from response surface analysis indicated that an optimum degradation efficiency of about 93% can be obtained at a concentration, pH, and catalyst dosage of 0.125 M, 2, and 0.20 g respectively, at 0.902 desirabilities. The Langmuir-Hinshelwood, modified Freundlich, parabolic diffusion, pseudo-first-/second-order, and zero-, first-, and second-order kinetic parameters were tested to ascertain the best model that best described the experimental data. Consequently, the Langmuir-Hinshelwood, modified Freundlich, and pseudo-second-order models were accepted based on the minimum error and higher R2 values. Based on the Langmuir-Hinshelwood rate constants for adsorption and photodegradation as well as the evaluated valence bond potential, the degradation of the drug first proceeded through the mechanism of adsorption and followed by the oxidation of the drug by superoxide (generated from the interaction of electrons that generated by through the absorption of UV radiation). The quantum chemical calculation gave evidence that pointed towards the establishment of strong agreement with experimental data and also showed that the carboxyl functional group in the drug is the target site for adsorption and subsequent degradation.

Sequestration of heavy metal ions from multi-metal simulated wastewater systems using processed agricultural biomass.

Industrial effluents generally contain several metals, so during adsorptive treatment, they may influence the removal of each other. It is essential to explore the effect of co-cations on metal removal in multi-metal solutions. The present study examined the possibility of processed rice husk and saw dust to remove Cr6+, Ni2+, Cu2+, Cd2+ and Zn2+, from the single, binary and multi-component aqueous solutions. A substantial lesser removal of metal ions was observed in the presence of co-ions. This study revealed antagonistic effect on the removal of a particular metal ion, from the industrial effluent, even at optimum process parameters if other metal ions are present in the effluent. Although, a higher concentration of one metal ion than others in effluents increased its removal due to a greater number of ions as compared to other for the biosorption, yet presence of other ions influences the uptake of individual ions. In case of industrial effluents, maximum adsorption was obtained at pH 2.0 for Cr6+, 5.0 for Ni2+ and Cd2+ and 6.0 for Zn2+ and Cu2+. The study confirms the beneficial use of the studied biosorbents in water remediation.

Biomedical and catalytic applications of agri-based biosynthesized silver nanoparticles.

Nanotechnology has been recognized as the emerging field for the synthesis, designing, and manipulation of particle structure at the nanoscale. Its rapid development is also expected to revolutionize industries such as applied physics, mechanics, chemistry, and electronics engineering with suitably tailoring various nanomaterials. Inorganic nanoparticles such as silver nanoparticles (Ag-NPs) have garnered more interest with their diverse applications. In correspondence to green chemistry, researchers prioritize green synthetic techniques over conventional ones due to their eco-friendly and sustainable potential. Green-synthesized NPs have proven more beneficial than those synthesized by conventional methods because of capping by secondary metabolites. The present study reviews the various means being used by the researchers for the green synthesis of Ag-NPs. The morphological characteristics of these NPs as obtained from numerous characterization techniques have been explored. The potential applications of bio-synthesized Ag-NPs viz. Antimicrobial, antioxidant, catalytic, and water remediation along with the plausible mechanisms have been discussed. In addition, toxicity analysis and biomedical applications of these NPs have also been reviewed to provide a detailed overview. The study signifies that biosynthesized Ag-NPs can be efficiently used for various applications in the biomedical and industrial sectors as an environment-friendly and efficient tool.

Adsorption of Indigo Carmine Dye by Acacia nilotica sawdust activated carbon in fixed bed column.

A continuous mode fixed-bed up-flow column adsorption analysis was conducted utilizing Acacia nilotica sawdust activated carbon (ASAC) as an adsorbent for the adsorption treatment of toxic Indigo Carmine Dye (ICD). The effect on the adsorption characteristics of ASAC of the influent ICD concentration, flow rate, and column bed depth has been investigated. According to the column study, the highest efficiency of ICD removal was approximately 79.01% at a preliminary concentration of 100 mg/L with a flow rate of 250 mL/h at a bed depth of 30 cm and adsorption power of 24.67 mg/g. The experimental work confirmed the dependency of break-through curves on dye concentration and flow rate for a given bed depth. Kinetic models were implemented by Thomas, Yoon-Nelson, and Bed-depth-service-time analysis along with error analysis to interpret experimental data for bed depth of 15 cm and 30 cm, ICD concentration of 100 mg/L and 200 mg/L and flow rate of 250 mL/h, and 500 mL/h. The analysis predicted the breakthrough curves using a regression basin. It indicated that all three models were comparable for the entire break-through curve depiction. The characteristic parameters determined by process design and error analysis revealed that the Thomas model was better followed by the BDST and Yoon-Nelson models in relating the procedure of ICD adsorption onto ASAC. B-E-T surface area and B-E-T pore volume of ASAC were 737.76 m2/g and 0.2583 cm3/g, respectively. S-E-M and X-R-D analysis reveal the micro-porous and amorphous nature of ASAC. F-T-I-R spectroscope indicate distinctive functional assemblies like -OH group, C-H bond, C-C bond, C-OH, and C-O groups on ASAC. It could be computed that the ASAC can be used efficiently as an alternative option for industrial wastewater treatment.

Study on potential applications and toxicity analysis of green synthesized nanoparticles.

Nanomaterials have garnered the significant interest of scientists owing to their technological as well as medical applications. In particular, metal and metal oxide nanoparticles have gained prominence because of their enhanced performance as compared to their bulk counterparts. Metal-supported nanomaterials are anticipated to make major contributions to solving today's most challenging issues, like energy harvesting and environmental remediation. The incorporation of nanoparticles into sensors has significantly enhanced their precision and selectivity. With the advent of green chemistry, green synthetic techniques have been prioritized for the synthesis of single and multicomponent nanomaterials. In the current review, we have addressed the multidimensional applications of nanoparticles in various sectors, including surface coatings, biosensing, environmental remediation, energy devices, construction, and nano probing, etc. This study focuses on the categorization of nanomaterials according to their source, dimensions, and composition, along with the exploration of synthetic modes. The eco-friendly and cost-effective greener route for the synthesis of nanoparticles has been explored in detail. Further, the antibacterial and cytotoxic potential has been addressed, and toxicity analysis has been conducted. The study signifies the augmented potential of green synthesized nanoparticles that can prove as economically viable and eco-friendly alternatives to conventional materials.

Study of Outcome of an Implanted Autologous Auricular Cartilage: A Preliminary Experimental Research in Rabbits.

To investigate the viability of the implanted crushed and uncrushed auricular cartilage graft with intact perichondrium with respect to macroscopic and microscopic parameters. Cartilage grafts from 8 white New Zealand rabbits were harvested from the right auricle, with intact perichondrial layers. There were two categories Pre implant and Post-implant and two types, mildly crushed and uncrushed cartilage graft. The cartilage grafts were implanted into the subcutaneous pockets over the right upper paraspinal area. At the end of 2 months, implanted grafts were retrieved and examined histopathologically. There was a difference among the both types of cartilages in both the categories with respect to chronic inflammation, fibrosis, cartilage mass viability and vascularization. The mildly crushed auricular autologous cartilage with intact perichondrium does not lose the viability and maintains the structural integrity and thus increasing the clinical predictability for cosmetic correction of nose in rhinoplasty.