Silver/quartz nanocomposite as an adsorbent for removal of mercury (II) ions from aqueous solutions

Nanocellulose-stabilized nanocomposites for effective Hg(II) removal and detection: a comprehensive review

Mercury pollution, with India ranked as the world's second-largest emitter, poses a critical environmental and public health challenge and underscores the need for rigorous research and effective mitigation strategies. Nanocellulose is derived from cellulose, the most abundant natural polymer on earth, and stands out as an excellent choice for mercury ion remediation due to its remarkable adsorption capacity, which is attributed to its high specific surface area and abundant functional groups, enabling efficient Hg(II) ion removal from contaminated water sources. This review paper investigates the compelling potential of nanocellulose as a scavenging tool for Hg(II) ion contamination. The comprehensive examination encompasses the fundamental attributes of nanocellulose, its diverse fabrication techniques, and the innovative development methods of nanocellulose-based nanocomposites. The paper further delves into the mechanisms that underlie Hg removal using nanocellulose, as well as the integration of nanocellulose in Hg detection methodologies, and also acknowledges the substantial challenges that lie ahead. This review aims to pave the way for sustainable solutions in mitigating Hg contamination using nanocellulose-based nanocomposites to address the global context of this environmental concern.

Nanoscale sulfur alleviates silver nanoparticle toxicity and improves seed and oil yield in Soybean (Glycine max)

Silver nanoparticles (AgNPs) are commonly used in many commercial products due to their antimicrobial properties, and their significant exposure in agricultural systems is anticipated. AgNPs accumulation in soil and subsequent uptake by plants can be harmful to plant growth and exposure to animals and humans through the food chain is a major concern. This study evaluated the potential protective role of nanosulfur (NS) and bulk sulfur (BS) at 200 and 400 mg/kg soil application in alleviating silver nanoparticle (AgNPs; 32 and 64 mg/kg) phytotoxicity to soybean [Glycine max (L) Merr.]. The treatments were added in the soil before soybean transplantation; growth, yield, nutrient, and silver accumulation were measured in the shoot, root, and seeds. Exposure to AgNPs significantly affected plant growth and yield, reducing nodule weight by 40%, fresh shoot weight by 66%, and seed yield by 68% when compared to controls. However, nanosulfur application in soil alleviated AgNPs toxicity, and importantly, this impact was nanoscale specific at the higher concentration because the benefits of corresponding bulk sulfur (BS) treatments were marginal. Specifically, nanosulfur at 400 mg/kg significantly increased seed yield (∼3-fold more than AgNP at 64 mg/kg) and shoot biomass (2.6-fold more than AgNP at 64 mg/kg) upon co-exposure with AgNPs, essentially alleviating AgNPs toxicity. Moreover, NS increased nodule mass by 3.5 times compared to AgNPs-treated plants, which was 170% greater than the Ag- and NS-free controls. Plants treated with NS with AgNPs co-exposure accumulated significantly less Ag in the shoots (∼80% reduction) and roots (∼95% reduction); no Ag contents were detected in seeds. These findings demonstrate the potential of sulfur, especially NS, as a sustainable soil amendment to reduce the accumulation and toxicity of AgNPs and as a valuable nano-enabled strategy to promote food safety and security.

Surface modification of quartz sand: A review of its progress and its effect on heavy metal adsorption

Quartz sand (SiO₂) is a prevalent filtration medium, boasting wide accessibility, superior stability, and cost-effectiveness. However, its utility is often curtailed by its sleek surface, limited active sites, and swift saturation of adsorption sites. This review outlines the prevalent strategies and agents for quartz sand surface modification and provides a comprehensive analysis of the various modification reagents and their operative mechanisms. It delves into the mechanism and utility of surface-modified quartz sand for adsorbing heavy metal ions (HMIs). It is found that the reported modifiers usually form connections with the surface of quartz sand through electrostatic forces, van der Waals forces, pore filling, chemical bonding, and/or molecular entanglement. The literature suggests that these modifications effectively address issues inherent to natural quartz sand, such as its low superficial coarseness, rapid adsorption site saturation, and limited adsorption capacity. Regrettably, comprehensive investigations into the particle size, regenerative capabilities, and application costs of surface-modified quartz sand and the critical factors for its wider adoption are lacking in most reports. The adsorption mechanisms indicate that surface-modified quartz sand primarily removes HMIs from aqueous solutions through surface complexation, ion exchange, and electrostatic and gravitational forces. However, these findings were derived under controlled laboratory conditions, and practical applications for treating real wastewater necessitate overcoming further laboratory-scale obstacles. Finally, this review outlines the limitations of partially surface modified quartz sand and suggests potential venues for future developments, providing a valuable reference for the advancement of cost-effective, HMI-absorbing, surface-modified quartz sand filter media.

Sonochemical oxidation and stabilization of liquid elemental mercury in water and soil

Over 3000 mercury (Hg)-contaminated sites worldwide contain liquid metallic Hg [Hg(0)_l] representing a continuous source of elemental Hg(0) in the environment through volatilization and solubilization in water. Currently, there are few effective treatment technologies available to remove or sequester Hg(0)_l in situ. We investigated sonochemical treatments coupled with complexing agents, polysulfide and sulfide, in oxidizing Hg(0)_l and stabilizing Hg in water, soil and quartz sand. Results indicate that sonication is highly effective in breaking up and oxidizing liquid Hg(0)_l beads via acoustic cavitation, particularly in the presence of polysulfide. Without complexing agents, sonication caused only minor oxidation of Hg(0)_l but increased headspace gaseous Hg(0)_g and dissolved Hg(0)_aq in water. However, the presence of polysulfide essentially stopped Hg(0) volatilization and solubilization. As a charged polymer, polysulfide was more effective than sulfide in oxidizing Hg(0)_l and subsequently stabilizing the precipitated metacinnabar (β-HgS) nanocrystals. Sonochemical treatments with sulfide yielded incomplete oxidation of Hg(0)_l, likely resulting from the formation of HgS coatings on the dispersed µm-size Hg(0)_l bead surfaces. Sonication with polysulfide also resulted in rapid oxidation of Hg(0)_l and precipitation of HgS in quartz sand and in the Hg(0)_l-contaminated soil. This research indicates that sonochemical treatment with polysulfide could be an effective means in rapidly converting Hg(0)_l to insoluble HgS precipitates in water and sediments, thereby preventing its further emission and release to the environment. We suggest that future studies are performed to confirm its technical feasibility and treatment efficacy for remediation applications.

Biogeneration of silver nanoparticles from Cuphea procumbens for biomedical and environmental applications

Nanotechnology is one of the most important and relevant disciplines today due to the specific electrical, optical, magnetic, chemical, mechanical and biomedical properties of nanoparticles. In the present study we demonstrate the efficacy of Cuphea procumbens to biogenerate silver nanoparticles (AgNPs) with antibacterial and antitumor activity. These nanoparticles were synthesized using the aqueous extract of C. procumbens as reducing agent and silver nitrate as oxidizing agent. The Transmission Electron Microscopy demonstrated that the biogenic AgNPs were predominantly quasi-spherical with an average particle size of 23.45 nm. The surface plasmonic resonance was analyzed by ultraviolet visible spectroscopy (UV-Vis) observing a maximum absorption band at 441 nm and Infrared Spectroscopy (FT IR) was used in order to structurally identify the functional groups of some compounds involved in the formation of nanoparticles. The AgNPs demonstrated to have antibacterial activity against the pathogenic bacteria Escherichia coli and Staphylococcus aureus, identifying the maximum zone of inhibition at the concentration of 0.225 and 0.158 µg/mL respectively. Moreover, compared to the extract, AgNPs exhibited better antitumor activity and higher therapeutic index (TI) against several tumor cell lines such as human breast carcinoma MCF-7 (IC₅₀ of 2.56 µg/mL, TI of 27.65 µg/mL), MDA-MB-468 (IC₅₀ of 2.25 µg/mL, TI of 31.53 µg/mL), human colon carcinoma HCT-116 (IC₅₀ of 1.38 µg/mL, TI of 51.07 µg/mL) and melanoma A-375 (IC₅₀ of 6.51 µg/mL, TI of 10.89 µg/mL). This fact is of great since it will reduce the side effects derived from the treatment. In addition, AgNPs revealed to have a photocatalytic activity of the dyes congo red (10^-3 M) in 5 min and malachite green (10^-3 M) in 7 min. Additionally, the degradation percentages were obtained, which were 86.61% for congo red and 82.11% for malachite green. Overall, our results demonstrated for the first time that C. procumbens biogenerated nanoparticles are excellent candidates for several biomedical and environmental applications.

Nanotechnology- A ray of hope for heavy metals removal

Environmental effects of heavy metal pollution are considered as a widespread problem throughout the world, as it jeopardizes human health and also reduces the sustainability of a cleaner environment. Removal of such noxious pollutants from wastewater is pivotal because it provides a propitious solution for a cleaner environment and water scarcity. Adsorption treatment plays a significant role in water remediation due to its potent treatment and low cost of adsorbents. In the last two decades, researchers have been highly focused on the modification of adsorption treatment by functionalized and surface-modified nanomaterials which has spurred intense research. The characteristics of nano adsorbents attract global scientists as it is also economically viable. This review shines its light on the functionalized nanomaterials application for heavy metals removal from wastewater and also highlights the importance of regeneration of nanomaterials in the view of visualizing the economic aspects along with a cleaner environment. The review also focused on the proper disposal of nanomaterials with crucial issues that persist in the adsorption process and also emphasize future research modification at a large-scale application in industries.

Green synthesis, characterization, and application of metal oxide nanoparticles for mercury removal from aqueous solution

In this work, a novel surface-modified, green-based wheat straw-supported magnetite nanoparticles (Fe₃O₄-NPs) were synthesized via the green synthesis method, and the adsorption of mercury (Hg(II)) ion from aqueous solutions was methodically investigated. The synthesized wheat straw-supported magnetite (Fe₃O₄-WSS) NPs were characterized using X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and scanning electron microscopic (SEM) methods. FT-IR and TGA confirmed that the surface of Fe₃O₄-NPs was functionalized well. The XRD analysis revealed the existence of magnetite in the synthesized wheat straw-supported Fe₃O₄-NPs of 19.83 nm average crystalline size. SEM analysis showed Fe₃O₄-NPs were almost spherical, with an average particle size of 22.48 nm. Adsorption studies were carried out to investigate the adsorption of Hg(II) ions onto Fe₃O₄-WSS NPs and the effect of various adsorption parameters such as pH, time, adsorbent dosage, and Hg(II) ion concentration. The optimum adsorption conditions were obtained: pH of 6, contact time of 45 min, adsorbate of 40 mg/L, and adsorbent of 1 g. A maximum of 98.04% Hg(II) ion removal efficiency was obtained at these optimum conditions. FT-IR analysis also indicated that surface functional groups such as C = C,-OH, and C-C of the newly produced Fe₃O₄-NPs led to the more efficient removal of Hg(II) from aqueous solution. The synthesized nano-adsorbent showed an excellent adsorption capability of 101.01 mg/g. Hg(II) ions adsorption onto Fe₃O₄-WSS NPs fitted well with the Langmuir adsorption isotherm model. Therefore, these reasonable findings reveal that Fe₃O₄-WSS NPs are an efficient and promising adsorbent for Hg(II) removal from aqueous water environments.

Recent advances in nanomaterial developments for efficient removal of Hg(II) from water

"Water" contamination by mercury Hg(II) has become the biggest concern due to its severe toxicities on public health. There are different conventional techniques like ion exchange, reverse osmosis, and filtration that have been used for the elimination of Hg(II) from the aqueous solutions. Although, these techniques have some drawbacks during the remediation of Hg(II) present in water. Adsorption could be a better option for the elimination of Hg(II) from the aqueous solutions. "Conventional adsorbents" like zeolite, clay, and activated carbons are inefficient for this purpose. Recently, nanomaterials have attracted attention for the elimination of Hg(II) from the aqueous solutions due to high porosity, better surface properties, and high efficiency. In this review, a thorough discussion has been carried out on the synthesis and characterization of nanomaterials along with mechanisms involved in the elimination of Hg(II) from aqueous solutions.

Recent Advances in Adsorptive Nanocomposite Membranes for Heavy Metals Ion Removal from Contaminated Water: A Comprehensive Review

Water contamination is one of the most urgent concerns confronting the world today. Heavy metal poisoning of aquatic systems has piqued the interest of various researchers due to the high toxicity and carcinogenic consequences it has on living organisms. Due to their exceptional attributes such as strong reactivity, huge surface area, and outstanding mechanical properties, nanomaterials are being produced and employed in water treatment. In this review, recent advances in the use of nanomaterials in nanoadsorptive membrane systems for wastewater treatment and heavy metal removal are extensively discussed. These materials include carbon-based nanostructures, metal nanoparticles, metal oxide nanoparticles, nanocomposites, and layered double hydroxide-based compounds. Furthermore, the relevant properties of the nanostructures and the implications on their performance for water treatment and contamination removal are highlighted. The hydrophilicity, pore size, skin thickness, porosity, and surface roughness of these nanostructures can help the water permeability of the nanoadsorptive membrane. Other properties such as surface charge modification and mechanical strength can improve the metal adsorption effectiveness of nanoadsorptive membranes during wastewater treatment. Various nanocomposite membrane fabrication techniques are also reviewed. This study is important because it gives important information on the roles of nanomaterials and nanostructures in heavy metal removal and wastewater treatment.

A unique, inexpensive, and abundantly available adsorbent: composite of synthesized silver nanoparticles (AgNPs) and banana leaves powder (BLP)

The purpose of this study is to investigate the development of a new and inexpensive adsorbent by immobilization synthesized silver nanoparticles (AgNPs) onto banana leaves powder (BLP), and the prepared composite (BLP)/(AgNPs) was used as an adsorbent for Zn(II), Pb(II), and Fe(III) ion removal from aqueous solutions under the influence of various reaction conditions. (BLP)/(AgNPs) demonstrated remarkable sensitivity toward Zn (II), Pb (II), and Fe (III) ions; metal ions eliminations increased with increasing contact time, agitation speed, adsorbent dose, and temperature, yielding adequate selectivity and ideal removal efficiency of 79%, 88%, and 91% for Zn (II), Pb (II), and Fe (III) ions, respectively, at pH = 5 for Zn(II) and pH = 6 for Pb(II), and Fe(III). The equilibrium contact time for elimination of Zn (II), Pb (II), and Fe (III) ions was reaches at 40 min. Langmuir, Freundlich, and Temkin equations were used to test the obtained experimental data. Langmuir isotherm model was found to be more accurate in representing the data of Zn(II), Pb(II), and Fe(III) ions adsorption onto (BLP)/(AgNPs), with a regression coefficient (R² = 0.999) and maximum adsorption capacities of 190, 244, and 228 mg/g for Zn(II), Pb(II), and Fe(III) ions, respectively. The thermodynamic parameters proved that adsorption of metal ions is spontaneous, feasible, and endothermic, whereas Kinetic studies revealed that the process was best described by a pseudo second order kinetics.

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By reduction reaction, silver nanoparticles were impregnated in banana leaves homogeneous powder and used as an adsorbent.

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The fabricated composites are used as adsorbent for the removal of Zn (II), Pb (II), and Fe (III) ions from aqueous solutions.

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The new adsorbent exhibited high adsorption capacity with three metal ions and followed the order Pb (II)> Fe (III) >Zn (II) ions.

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The metal ions vanished from the solution within approximately 40 min.

Advancements in heavy metals removal from effluents employing nano-adsorbents: Way towards cleaner production

Due to the development in science field which gives not only benefit but also introducesundesirable pollution to the environment. This pollution is due to poor discharge activities of industrial effluents into the soil and water bodies, surface run off from fields of agricultural lands, dumping of untreated wastes by municipalities, and mining activites, which deteriorates the cardinal virtue of our environment and causes menace to human health and life. Heavy metal(s), a natural constituent on earth's crust and economic important mineral, due to its recalcitrant effects creates heavy metal pollution which affects food chain and also reduces the quality of water. For this, many researchers have performed studies to find efficient methods for wastewater remediation. One of the most promising methods from economic point of view is adsorption, which is simple in design, but leads to use of a wide range of adsorbents and ease of operations. Due to advances in nanotechnology, many nanomaterials were used as adsorbents for wastewater remediation, because of their efficiency. Many researchers have reported that nanoadsorbents are unmitigatedly a fruitful solution to address this world's problem. This review presents a potent view on various classes of nanoadsorbents and their application to wastewater treatment. It provides a bird's eye view of the suitability of different types of nanomaterials for remediation of wastewater and Backspace gives up-to-date information about polymer based and silica-based nanoadsorbents.

Green and facile synthesis of gold/perlite nanocomposite using Allium Fistulosum L. for photothermal application

Photothermal therapy (PTT) procedure is anticipated as a new generation of cancer therapy techniques. With this in mind, in this work, an effective drug-free approach was developed to kill MCF7 breast cancer cells using PTT. A novel biocompatible nanocomposite as a PTT transducer was prepared from the in situ phytosynthesis of gold nanoparticles (Au NPs) in the presence of perlite as a platform and extract of Allium Fistulosum L. as a stabilizing and reducing agent (Au/perlite NC). The common characterization techniques such as Fourier transform infrared (FT-IR), zeta potential, dynamic light scattering (DLS), X-ray diffraction (XRD), ultraviolet-visible (UV-vis), scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) were used to approve the synthesis of Au/perlite NC. The potential of the synthesized NCs on ROS generating and antioxidant activity was assessed by DPPH. In the following, the PTT efficacy of the Au/perlite NC on the destruction of MCF-7 breast cancer cells was assessed in vitro via the cell cycle, cell viability, and DAPI staining assays. The DPPH assay results showed that Au/perlite NC had a radicals scavenging capacity of about 41.47 % in 30 min. Cellular uptake results indicated a significant cell uptake after 1.5 h exposure with Au/perlite NC. Interestingly, cell death was increased dramatically by increasing irradiation time from 6 to 10 min. Cell viability assay revealed that the maximum number of cell death is around 50 % which was observed in the presence of Au/perlite NC by irradiation time of 10 min. Cell cycle results showed that the maximum amount of apoptotic cells (85 %) was observed in Au/perlite NC treatment group received laser irradiation for 10 min. The outcomes demonstrated that the Au/perlite NC can be used as a new drug-free and efficient agent for PTT of breast cancer cells without any concern cytotoxicity.

Adsorption of Cr(VI), Ni(II), Fe(II) and Cd(II) ions by KIAgNPs decorated MWCNTs in a batch and fixed bed process

The efficient removal of toxic metals ions from chemical industry wastewater is considered problematic due to the existence of pollutants as mixtures in the aqueous matrix, thus development of advanced and effective treatment method has been identified as a panacea to the lingering problems of heavy metal pollution. In this study, KIAgNPs decorated MWCNTs nano adsorbent was developed using combination of green chemistry protocol and chemical vapor deposition techniques and subsequently characterized using UV-Vis, HRTEM, HRSEM, XRD, FTIR and XPS. The adsorptive efficiency of MWCNTs-KIAgNPs for the removal of Cr(VI), Ni(II), Fe(II), Cd(II) and physico-chemical parameters like pH, TDS, COD, BOD, nitrates, sulphates, chlorides and phosphates from chemical industrial wastewater was examined in both batch and fixed bed systems. The result exhibited successful deposition of KIAgNPs on the surface of MWCNTs as confirmed by the microstructures, morphology, crystalline nature, functional groups and elemental characteristics of the MWCNTs-KIAgNPs. Optimum batch adsorption parameters include; pH (3 for Cr(VI) and 6 for Ni(II), Fe(II) and Cd(II) ions), contact time (60 min), adsorbent dosage (40 mg) and temperature (318 K). The binding capacities were obtained as follows; Cr⁶⁺ (229.540 mg/g), Ni²⁺ (174.784 mg/g), Fe²⁺ (149.552) and Cd²⁺ (121.026 mg/g), respectively. Langmuir isotherm and pseudo-second order kinetic model best described the experimental data in batch adsorption, while the thermodynamic parameters validated the chemisorption and endothermic nature of the adsorption process. In continuous adsorption, the metal ions were effectively removed at low metal influent concentration, low flow rate and high bed depth, whereby the experimental data were designated by Thomas model. The high physico-chemical parameters in the wastewater were successfully treated in both batch and fixed bed systems to fall within WHO permissible concentrations. The adsorption/desorption study illustrated over 80% metal removal by MWCNTs-KIAgNPs even after 8th adsorption cycle. This study demonstrated excellent performance of MWCNTs-KIAgNPs for chemical industry wastewater treatment.

Biogenic and chemically synthesized Solanum tuberosum peel-silver nanoparticle hybrid for the ultrasonic aided adsorption of bromophenol blue dye

This work was aimed at the synthesis of a hybrid (STpe-AgNP), obtained by impregnation of silver nanoparticles (AgNP) onto Solanum tuberosum peel (STpe), for the ultrasonic assisted adsorption of bromophenol blue (BB) dye. SEM, FTIR, XRD, EDX, TGA and BET techniques were used to characterize the adsorbents. The XRD, SEM and EDX confirmed successful impregnation of AgNPs onto STpe to form the hybrid. The AgNPs impregnated onto the hybrid were found to be water stable at various pH values of 2.0-9.0. Chi-square (χ2 < 0.024) and linear regression (R2 > 0.996) showed that the Freundlich model was best fitted among the isotherm models, corroborated by the oriented site model. Kinetic analysis conformed to the intraparticle diffusion and pseudo-first-order rate equations, while thermodynamics displayed a physical, spontaneous and endothermic adsorption process. The presence of competing Pb(II), Ni(II), Cd(II) and Zn(II) metal ions in solution interfered with the adsorption of BB onto the biosorbents. In terms of reusability, STpe and STpe-AgNP showed BB desorption of 91.3% and 88.5% respectively, using NaOH as eluent. Ultra-sonication significantly enhanced the adsorption of BB by both adsorbents, but the impregnation of AgNPs only slightly improved adsorption of the dye from the simulated wastewater. This study also illustrated that pristine STpe biomass waste is a cheap viable option for the decontamination of BB from water.

Synthesis and Antibacterial Activity of (AgCl, Ag)NPs/Diatomite Hybrid Composite

. In the present research, hybrid (AgCl, Ag)NPs/diatomite composites were synthesized by direct impregnation with aqueous silver nitrate solutions. The silver chloride nanoparticles (AgCl-NPs) were formed as an effect of the exchange reaction when silver interacted with the diatomite mineral impurity halite. Nanoparticles of metallic silver (AgNPs) were created by the reduction of silver ions under the influence of hydrogen peroxide. The content of silver chloride nanoparticles in the (AgCl, Ag)NPs/diatomite composite was limited by the content of the halite in the used diatomite. Samples of natural diatomite and synthesized (AgCl, Ag)NPs/diatomite composites were examined by using scanning electron microscopy, transmission electron microscopy, X-ray powder diffraction, infrared spectroscopy and thermogravimetric analysis. Moreover, the antibacterial potential of synthesized composites was also studied using the MIC (minimal inhibitory concentration) method against the most common drug-resistant microorganisms in the medical field: Gram-positive Staphylococcus aureus and Gram-negative Klebsiella pneumoniae. The obtained hybrid (AgCl, AgNPs)/diatomite composites were shown to have antimicrobial potential. However, widespread use requires further study by using various microorganisms and additional cytotoxic studies on eukaryotic systems, e.g., cell lines and animal models.