Removal Of Toxic Heavy Metals Research Articles

Uptake of selected heavy metals from contaminated waters utilizing cost-effective and environmentally friendly biosorbents prepared from the residues of a traditionally fermented Ethiopian alcoholic beverage (Tella)

In the current study, the adsorption capacity of Tella residues (residues of fermented alcoholic beverage) for quantitative uptake of Cu(II), Cd(II), Zn(II) and Pb(II) was evaluated. Chemical treatment of the local beer residue (LBR) has improved the removal efficiency of the adsorbent, which was achieved at pH = 5, 1.0 g adsorbent, 50 mg/L initial concentration, 180 min contact time and agitation speed of 100 rpm. The adsorption was found to fit the Langmuir adsorption isotherm model, and the theoretical equilibrium capacities were well fitted with the experimental equilibrium capacities, resulting in chemical adsorption (chemisorptions) on the adsorbent surface while the equilibrium kinetics follows the pseudo-second-order. The adsorption capacity (Qo) of LBR decreases in the following order: Zn(II) > Cu(II) > Pb(II) > Cd(II) as metal concentration ranged from 20-200 mg/L. Thermodynamic parameters, including standard free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) were calculated to predict the nature of adsorption. The negative values of ΔG° and the positive value of ΔH° indicate that the adsorption process was spontaneous and endothermic. Adsorption capacities were found to increase when the temperature ranged from 25-60 °C. Thus, the findings suggest a promising application of LBR as an alternative low-cost novel adsorbent for the removal of toxic heavy metals from wastewater.

Preparation of Polymeric Aluminum Chloride-Loaded Porous Carbon and Evaluation of Its Pb2+ Immobilization Mechanisms in Soil

In recent years, the remediation of heavy metal-contaminated soils has attracted great attention worldwide. Previous research on the removal of toxic heavy metals from wastewater effluents through adsorption by typical solid wastes (e.g., fly ash and coal gangue) has mainly focused on the control of wastewater pollutants. In this study, a coal gangue (CG) by-product from Hancheng City was used as a raw material to prepare polymeric aluminum chloride-loaded coal gangue-based porous carbon (PAC-CGPC) by hydrothermal synthesis. This material was subsequently employed to assess its performance in mitigating Pb2+ in soils. In addition, the effects of the pore structure of the prepared material on the adsorption rates, adsorption mechanisms, and plant root uptakes of soil Pb2+ were investigated in this study. The raw CG and prepared PAC-CGPC materials exhibited specific surface areas of 1.8997 and 152.7892 m2/g, respectively. The results of adsorption kinetics and isotherms indicate that the adsorption of Pb2+ based on PAC-CGPC mainly follows a pseudo-second-order kinetic model, suggesting that chemisorption may be the dominant process. In addition, the adsorption isotherm results showed that the Freundlich model explained better the adsorption process of Pb2+, suggests that the adsorption sites of lead ions on APC-CGPC are not uniformly distributed and tend to be enriched in APC, and also shows the ion exchange between aluminum and lead ions. The thermodynamic model fitting results demonstrated the occurrence of spontaneous and exothermic PAC-CGPC-based adsorption of Pb2+, involving ion exchange and surface complexation. The effects of the PAC-CGPC addition on soybean plants were further explored through pot experiments. The results revealed substantial decreases in the Pb2+ contents in the soybean organs (roots, stems, and leaves) following the addition of the PAC-CGPC material at a dose of 3% compared with the control and raw CG groups. Furthermore, the addition of the PAC-CGPC material at a dose of 3% effectively reduced the bioavailable Pb2+ content in the soil by 82.11 and enhanced soybean growth by 15.3%. These findings demonstrated the inhibition effect of the PAC-CGPC material on the translocation of Pb2+ in the soybean seedlings. The modified CG adsorbent has highly pore structure and good hydrophilicity, making it prone to migration in unsaturated soils and, consequently, enhancing Pb2+ immobilization. This research provides theoretical support for the development of CG-based materials capable of immobilizing soil pollutants.

Solid-State Fluorescent Organic Polymers for Visual Detection and Elimination of Heavy Metals in Water.

Selective sensing and removal of toxic heavy metals from water are highly essential since their presence poses significant health and environmental hazards. Herein, we designed and synthesized a novel fluorescent nonconjugated organic polymer by strategically incorporating two key functional groups, namely, a dansyl fluorophore and dithiocarbamate (DTC). Different characterization techniques, including 1H nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive X-ray analysis (EDAX), Fourier transform infrared (FTIR), and fluorescence spectroscopy, were performed to understand its structure and material properties. The quantum yield of 4.72% and its solid-state fluorescence indicate that it has potential for various applications in several technological and scientific domains. In this study, we investigated a specific application involving the detection and elimination of heavy metals from water. Interestingly, the presence of dansyl and DTC moieties demonstrated remarkable selectivity toward Cu2+, Co2+, Ni2+, Fe3+, and Fe2+ sensing, displaying distinct color changes specific to each metal. Cu2+ resulted in a yellow color, Co2+ showed a green color, Ni2+ displayed a pale yellowish-green color, and Fe2+/Fe3+ exhibited a brown color. The LOD (limit of detection) for each metal was obtained in the nanomolar range by using a fluorescence spectrometer and the micromolar range from UV-visible spectra: 13.27 nM and 0.518 μM for Cu2+, 8.27 nM and 0.581 μM for Co2+, 14.36 nM and 0.140 μM for Ni2+, 14.95 nM and 0.174 μM for Fe2+, and 15.54 nM and 0.33 μM for Fe3+. Moreover, the DTC functionality on its backbone facilitates effective interaction with the aforementioned heavy metals, subsequently removing them from water (except Fe2+ and Fe3+), validating its dual functionality as both an indicator and a purifier for heavy metals in water. The polymer exhibited a maximum adsorption capacity of 192.30 mg/g for Cu2+, 159.74 mg/g for Co2+, and 181.81 mg/g for Ni2+. Furthermore, this approach exhibits versatility in crafting fluorescent polymers with adjustable attributes that are suitable for a wide range of applications.

Novel High-Performance Functionalized and Grafted Bio-Based Chitosan Adsorbents for the Efficient and Selective Removal of Toxic Heavy Metals from Contaminated Water.

Novel functionalized and/or grafted crosslinked chitosan adsorbents were synthesized and used to remove several toxic heavy metal ions such as nickel, lead, chromium, and cadmium ions from contaminated water. The chitosan biopolymer was functionalized by maleic anhydride (CS_MA) acting also as a crosslinking agent. Glutaraldehyde-crosslinked chitosan (CS_GA) grafted with poly(methyl methacrylate) (CS_MMA) was also synthesized. The synthesized adsorbents were characterized using a variety of analytical techniques such as SEM, TGA, and FTIR, which confirmed their chemical structures and morphology. The adsorption capacity of the adsorbents was analyzed under various conditions of contact time, adsorbent dose, initial concertation, temperature, and pH and evaluated against those of pure chitosan (CS) and the crosslinked chitosan(CS_GA). The ultimate removal conditions were 0.5 g/100 mL adsorbent dose, an initial metal ion concentration of 50 ppm, a temperature of 45 °C, and pH 9. CS_MMA had the highest removal percentages for all metal ions, ranging from 92% to 94%. The adsorption was demonstrated to fit a pseudo-first-order model that followed a Langmuir adsorption isotherm. The results highlight the capacity of the synthesized polymers to efficiently remove major toxic contaminants at low cost from contaminated water, present especially in low-income areas, without harming the environment.

Removal of toxic heavy metal by a cost-free and eco-friendly BPAC nanoadsorbent

Removal of toxic heavy metal by a cost-free and eco-friendly BPAC nanoadsorbent

Lysine-functionalized graphene oxide on cost-effective microporous support: A hydrophilic and fouling resistant membrane for safe lead filtration

The presence of heavy metals in freshwater is a severe problem humanity faces. Remedies with high removal efficiency of heavy metals from contaminated water are crucial. However, existing studies often neglect effluent quality per World Health Organization (WHO) standards. Also, the reported conditions are either unrealistic to the actual contamination levels or unsuitable for large-scale applications. Here, we report the fabrication of zwitterionic graphene oxide (GO) by incorporating a pH-responsive group (i.e., Lysine) using N, N′-diisopropylcarbodiimide (DIC) as a coupling agent. The modified GO-Lys was then coated on a commercially available 0.45-μm Nylon membrane and was tested for selective removal of toxic heavy metals from synthetic water and human blood plasma samples while allowing essential metal ions. Consequently, lead was the most retained toxic metal (i.e., 99.99% retention with effluent quality meeting WHO standards) among nickel, arsenic, cadmium, and mercury (i.e., between 50 to 80% retention). These composite membranes also displayed excellent fouling resistance and inhibited bacterial adhesion onto the membrane surface, while maintaining stable performance over a long time and critical transmembrane pressure conditions. This research marks a significant advancement in environmental technologies, providing an effective solution for selectively removing heavy metal pollutants, with a particular focus on lead detoxification applications.

Hagenia abyssinica-Biomediated Synthesis of a Magnetic Fe3O4/NiO Nanoadsorbent for Adsorption of Lead from Wastewater.

Magnetic nanocomposite adsorbents are cost-effective, environmentally friendly, easy to use, and highly efficient at removing metals from large volumes of wastewater in a short time by using an external magnetic field. In this study, an Fe3O4/NiO composite nanoadsorbent was prepared by varying the mass percent ratios of NiO (50, 40, 30, 20%), which are denoted Fe3O4/50%NiO, Fe3O4/40%NiO, Fe3O4/30%NiO, and Fe3O4/20%NiO, respectively, using Hagenia abyssinica plant extract as the template/capping agent and a simple mechanical grinding technique. The nanocomposites were characterized using an X-ray diffractometer (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, nitrogen adsorption, and ζ-potential measurements. The adsorption performance of the nanoadsorbent was assessed for the removal of lead (Pb2+) ions from aqueous solutions. Among the composite adsorbents, Fe3O4/50%NiO demonstrated the best Pb(II) removal efficiency (96.65%) from aqueous solutions within 80 min at pH 8, at a 100 mg/L lead concentration and 0.09 g of adsorbent dose. However, with the same parameter, only 62.8% of Pb(II) was removed using Fe3O4 nanoparticles (NPs). The adsorptive performance indicated that the optimum amount of porous material (NiO) in the preparation of the Fe3O4/NiO composite nanoadsorbent, with the aid of H. abyssinica plant extract, enhances the removal of toxic heavy metals from aqueous solutions. Multiple isotherm and kinetic models were used to analyze the equilibrium data. Adsorption isotherm and kinetic studies were found to follow the Freundlich isotherm and pseudo-second-order kinetics, respectively.

Biosorption of halophilic fungal melanized membrane – PUR/melanin polymer for heavy metal detoxification with electrospinning technology

ABSTRACT Eradication of heavy metal pollution has become the prime priority over the conservation of water resources in the upcoming era. Herein, the study involved the halophilic fungal melanin from Curvularia lunata showed a promising biosorbent for the removal of toxic heavy metals which shows eco-friendly, cost-effective, high stability, and adsorbent efficiency. Polyurethane blended with fungal melanin polymers, makes polymeric nanofibrous membranes through electrospinning techniques. BET isotherms revealed the raw fungal melanin holds a surface area of 3.54 m2/g exhibiting type IV isotherms. BJH results in a total pore volume of 5.79 cc/g with a pore diameter of 6.54 ± 1 nm for pores smaller than 4544.8 Å. Exhibits Eumelanin properties were characterized by FE – SEM and FTIR functional elements. ICPMS confirmed the metal adsorption proficiency on both raw and melanized membranes before and after treatments. Over 17 heavy metals, Ni2+ were adsorbed with 100% efficiency by raw melanin alone with 42.48 µg/L of Ni2+ concentration in the water sample, whereas, Cu2+, Zn2+, Co2+, Cr2+, Pb2+, Mn2+, Al3+, Mo6+, Sb3+, Ba2+, Fe2+, and Mg2+ stands next with 99%. In this study, gentle/simple application of raw fungal melanin (without PUR tailored) can detoxify the maximum concentration of heavy metals present in the water bodies which are further used for irrigation and even drinking purposes. This mycoremediation approach can be easily adapted to industrial production than other high-performance membrane materials with minimal process modification, making it a promising strategy for improving the adsorption properties used in various applications after still furthermore investigation.

Review on Agrobiowaste‐mediated Nanohybrids for Removal of Toxic Heavy Metals from Wastewater

AbstractBecause of the growing population and the industrial revolution, a significant number of toxic materials including heavy metals (HMs) are being released into the environment, posing harm to humans, the environment, and other living organisms. When these HMs find their way into water sources, they cause water pollution and pose a threat to the ecosystem. As a result, there is an imperative need to eliminate these HMs from the water. Numerous techniques are being employed for water purification, but adsorption is the most economical and efficient method. The present article critically discussed the applications of different adsorbents including agricultural wastes, industrial wastes, biochar, chitosan, aerogel‐based adsorbents, geopolymer cement/concrete, carbon‐based nanomaterials (NMs), and polymer‐supported nanocomposites (NCs) for removal of HMs from wastewater. Removal capacity of some of the adsorbents are tabulated. Effects of dose of adsorbent, contact time, pH, temperature, initial ion concentration and ionic strength on the removal of HMs from water have been explored. Various adsorption isotherm and kinetic models have also been discussed, including the modeling using artificial neural networks.

Efficient removal and transformation of Cr(VI) from alkaline wastewater to form a ferrochromium spinel multiphase via a modified ferrite process

Chromium-containing wastewater causes serious environmental pollution due to the harmfulness of Cr(VI). The ferrite process is typically used to treat chromium-containing wastewater and recycle the valuable chromium metal. However, the current ferrite process is unable to fully transform Cr(VI) into chromium ferrite under mild reaction conditions. This paper proposes a novel ferrite process to treat chromium-containing wastewater and recover valuable chromium metal. The process combines FeSO4 reduction and hydrothermal treatment to remove Cr(VI) and form chromium ferrite composites. The Cr(VI) concentration in the wastewater was reduced from 1040 mg L−1 to 0.035 mg L−1, and the Cr(VI) leaching toxicity of the precipitate was 0.21 mg L−1 under optimal hydrothermal conditions. The precipitate consisted of micron-sized ferrochromium spinel multiphase with polyhedral structure. The mechanism of Cr(VI) removal involved three steps: 1) partial oxidation of FeSO4 to Fe(III) hydroxide and oxy-hydroxide; 2) reduction of Cr(VI) by FeSO4 to Cr(III) and Fe(III) precipitates; 3) transformation and growth of the precipitates into chromium ferrite composites. This process meets the release standards of industrial wastewater and hazardous waste and can improve the efficiency of the ferrite process for toxic heavy metal removal.

Synthesis and characterizations of molybdenum-doped titanium dioxide nanoparticles for photocatalytic removal of chromium (VI) from aqueous solutions

The photocatalytic removal of toxic heavy metals using titanium dioxide nanoparticles is an emerging technology for environmental remediation. Pure and Mo-doped TiO2 nanoparticles were synthesized using a modified sol-gel process, and then characterized by field emission scanning electron microscopy (FE-SEM) and particle size analysis (PSA) to determine their morphology and size, while X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS) were used to determine their crystalline phase and composition. Brunauer–Emmett–Teller (BET) analysis was used to measure the surface area and porosity of the synthesized catalysts applying Langmuir and BET models. The catalyst was mainly composed of spherical anatase TiO2 particles, with a diameter in the range of 15–75 nm, and the maximum doping percentage of Mo was 3.3%. The Langmuir surface area of pure and Mo-doped TiO2was 91.63 and 128.73 m2/g, and the average pore volume was 0.029 and 0.032 cm3/g, respectively. The nanomaterials were used in the photocatalytic removal of Cr(VI) from aqueous solutions, and the adsorption isotherms indicated that the catalyst uptake (qe,max) amounts for Mo-doped TiO2 and pure TiO2 were 12.5 and 6.5 mg/L, respectively. Moreover, the equilibrium removal percentage was improved from 41% for pure TiO2 to 90% for Mo-doped TiO2, which confirms that photocatalytic activity is enhanced by doping TiO2 with molybdenum.

Optimized synthesis of cysteine-functionalized nanocrystalline hydroxyapatite for synchronous decontamination of Cd(II) and Pb(II)

The synchronous removal of toxic heavy metals (e.g., cadmium (Cd), lead (Pb), and etc.) from the contaminated water environment is an urgent demand in the pollution control field. Herein, an innovative adsorbent synthesis idea was proposed and a series of cysteine-functionalized nanohydroxyapatite (CysHAP) composites were prepared by adopting different reaction temperatures, cysteine/HAP ratios, and synthesis methods. According to the single factor tests, a co-precipitation temperature of 25 °C with a molar cysteine/HAP ratio of 2.0 was selected to synthesize the optimum CysHAP2.0–25 composite. Multiple characterization results showed that cysteine markedly altered the morphology, crystallinity, and crystal structure of HAP, leading to the formation of CysHAP2.0–25 composite with a superior dispersity, a smaller crystal size, a higher specific surface area, and a greater number of binding sites. Compared with HAP-25, the CysHAP2.0–25 composite exhibited a better Cd(II) sorption performance and a 100% Pb(II) removal in a wide range of solution pH and background electrolyte concentration. The removal performance of CysHAP2.0–25 composite towards Cd(II) was suppressed by the coexisting aqueous components with an obviously stronger inhibiting action of humic acid (HA) than low molecular weight organic acids (LMWOAs) and mixed inorganic components (IC). Pb(II) slightly reduced the sorption ratio of Cd(II) and forced Cd(II) to bind on the -SOx sites derived from sulfhydryl oxidation. In contrast, Cd(II) had no impact on the sorption behaviors of Pb(II). Overall, the synthesized CysHAP2.0–25 composite could be potential applied for the purification of Cd- and Pb-bearing water systems.

Study of modified biomass of Gossypium hirsutum as heavy metal biosorbent

The presence of heavy metals in aqueous media can cause serious threats to living organisms. Consequently, for the efficient and economic removal of heavy metals from water, a wide range of biomass as biosorbents has been investigated. The present study was designed to deploy Gossypium hirsutum stem powder as a biosorbent for efficient removal of toxic heavy metals including Pb2+, Cu2+, Zn2+ and Ni2+ ions from aqueous media. The biomass was modified through acid and base treatment prior to its deployment as biosorbent. Different instrumental techniques such as FTIR, SEM and TGA were used to analyze the structural, morphological, and thermal characteristics of biosorbent. AAS, and UV spectrophotometer were used to quantify the metal ions in solutions. Nonlinear models of Langmuir and Freundlich isotherms was explored for practical use in real sample analysis, and adsorption parameters were optimized systematically. The adsorption isotherms followed the non-linear Langmuir model, which best fit four heavy metals with an R2 value (0.99) in both acidic and base-modified biomass. The base treated biomass showed relatively higher maximum uptake capacity for the investigated heavy metals (Pb2+ 121.24, Cu2+ 117.09, Zn2+ 130.65, and Ni2+ 111.09 mg g−1) than that of acid treated biomass. Thermogravimetric analysis revealed the degradation pattern of designed adsorbent. Fourier transform infrared spectroscopy confirmed the presence of OH and Cl groups which were added during pretreatment. Scanning electron microscopy showed that the modified material has rough surface area which can contribute in enhancing the adsorption of heavy metals. The regeneration studies of modified biosorbent using 0.1 M HNO3 solution demonstrated that the biosorbent can be effectively utilized for further five biosorption cycles without significant loss in its adsorption capability. The findings of the study revealed that acid and base modified Gossypium hirsutum stem could be efficiently utilized as a biosorbent for the removal of heavy metals in water at pH 5.5 with an adsorbent dose of 0.5 g and equilibrium time of 35 min.

Facile and efficient synthesis of carboxylic terminated Ti3C2Tx nanosheets using citric acid

For the last decade, researchers have been reporting various approaches for the synthesis and surface modification of Ti3C2Tx MXenes nanosheets. However, the use of concentrated acids and alkalis, elevated reaction temperature, and the subsequent degradation of MXenes nanosheets are considered sore points of the trade. In this study, we formulated an original, efficient, and one-pot protocol for the synthesis of carboxylic terminated Ti3C2Tx nanosheets incorporating non-hazardous citric acid with NH4HF2. Three different etchants: (i) NH4HF2 (ii) NH4HF2 and citric acid (iii) NH4F and citric acid, were used to etch the Ti3AlC2 MAX phase. Thus, three types of Ti3C2Tx nanosheets were synthesized and comparatively analyzed using XRD, SEM, TEM, EDX, AFM, FTIR, XPS, NMR, BET, TGA and AAS techniques. Firstly, it was established that among Ti3C2Tx samples, the best-exfoliated few-layered carboxylic terminated nanosheets of 1.36 nm thickness were achieved using NH4HF2 and citric acid. Secondly, the nanosheets displayed extraordinary features owing to their superior morphology, microporous structure, improved surface chemistry, better thermal stability, prolonged dispersity and enhanced adsorption performance in an aqueous media. For instance, the Ti3C2Tx nanosheets showed a d-spacing of 1.25 nm and a specific surface area of 42.63 m2/g with numerous active sites in terms of (–COOH) terminations alongside (=O), (-F) and (–OH) terminal groups. In addition, the carboxylic terminated MXene exhibited excellent dispersity and stability in water for 40 days. The nanosheets also displayed adsorption capacities of 338 mg/g and 349 mg/g for Cr(VI) and Pb(II), respectively. The adsorption performance of the MXenes nanosheets was quite encouraging compared to previous studies. Moreover, the carboxylic terminated nanosheets were regenerated over six cycles of adsorption–desorption. Hence, these high-quality Ti3C2Tx nanosheets are a promising candidate for environmental application in general and removal of toxic heavy metals from wastewater in specific.

Nano-Phytoremediation of Heavy Metals from Soil: A Critical Review

Heavy metal pollution is one of the major global issues arising from various anthropogenic activities. The natural habitat and human health may be at peril from heavy metal exposure since they are tenacious, bio-accumulative, and non-biodegradable. Therefore, eradicating heavy metals from the soil ecosystem is a crucial responsibility to create a secure, viable, and zero-waste ecosystem. There are numerous techniques for eliminating heavy metals from the environment, but each has its own benefits and drawbacks. When a biological agent is used to degrade pollutants, this process is called bioremediation. Nano-phytoremediation, an emerging bioremediation approach in the field of nanotechnology, uses biosynthesized nanoparticles and plant species for the removal of toxic heavy metals from the environment. It is an efficient, economical, and environmentally friendly technique. The adverse consequences of metal exposure on different plant species have been discovered to be greatly reduced by engineered nanomaterials. Because of their tiny dimensions and huge surface area, nanomaterials have an attraction towards metals and can thus quickly enter the contaminated zone of ecosystems that are metal-challenged. The current review provides an overview of various aspects of nano-phytoremediation for heavy metal remediation.

RSM optimization studies for cadmium ions adsorption onto pristine and acid-modified kaolinite clay

Clay has been reported as an active absorbent for the removal of toxic heavy metals from aqueous medium. In this study, pristine and acid modified kaolinite clays (PKC and AMKC) were prepared, characterized using various analyses, and tested for Cd2+ ion adsorption from textile industry wastewater. After acid modification, the specific surface area of clay increased from 84.2 to 389.4 m2/g. Adsorption isotherm, kinetics and thermodynamics behaviour process were examined. The pH at (pHpzc) of 8.5 indicate that AMKC surface is positively charged for pH below the pHpzc attracting anions. Response surface methodology was used to investigate the effect of adsorption process factors on Cd2+ ion removal uptake. At the optimum process conditions of 45.3 °C temperature, 0.63 g/L adsorbent dosage, and 120.9 min contact time, the percentages of Cd2+ adsorbed by PKC and AMKC were 77.82% and 99.19%, respectively. Various models were employed to analyzed the kinetic and equilibrium data. The Pseudo-first order, Pseudo-second order and Intra-particle diffusion were used to evaluate the kinetic data, while the Langmuir, Freundlich and Temkin isotherm models were applied to analyzed the equilibrium data. The sorption kinetics was found to be best described by Pseudo-second order considering the high correlation coefficient (R2), smaller Chi-square (ᵪ2) and sum of square error (SSE). The Freundlich model was the most accurate in describing the equilibrium data followed by Langmuir and Temkin respectively. The thermodynamic reveal that the reaction is spontaneous and endothermic in nature, and increase in randomness between the adsorbent and adsorbate. The obtained activation energy (Ea) value suggest that the adsorption mechanism of Cd(II) is a physisorption dominated.

Synthesis and Characterization of MC/TiO2 NPs Nanocomposite for Removal of Pb2+ and Reuse of Spent Adsorbent for Blood Fingerprint Detection.

The removal of toxic heavy metals from wastewater through the use of novel adsorbents is expensive. The challenge arises after the heavy metal is removed by the adsorbent, and the fate of the adsorbent is not taken care of. This may create secondary pollution. The study aimed to prepare mesoporous carbon (MC) from macadamia nutshells coated with titanium dioxide nanoparticles (TiO2 NPs) using a hydrothermal method to remove Pb2+ and to test the effectiveness of reusing the lead-loaded spent adsorbent (Pb2+-MC/TiO2 NP nanocomposite) in blood fingerprint detection. The samples were characterized using SEM, which confirmed spherical and flower-like structures of the nanomaterials, whereas TEM confirmed a particle size of 5 nm. The presence of functional groups such as C and Ti and a crystalline size of 4 nm were confirmed by FTIR and XRD, respectively. The surface area of 1283.822 m2/g for the MC/TiO2 NP nanocomposite was examined by BET. The removal of Pb2+ at pH 4 and the dosage of 1.6 g/L with the highest percentage removal of 98% were analyzed by ICP-OES. The Langmuir isotherm model best fit the experimental data, and the maximum adsorption capacity of the MC/TiO2 NP nanocomposite was 168.919 mg/g. The adsorption followed the pseudo-second-order kinetic model. The ΔH° (-54.783) represented the exothermic nature, and ΔG° (-0.133 to -4.743) indicated that the adsorption process is spontaneous. In the blood fingerprint detection, the fingerprint details were more visible after applying the Pb2+-MC/TiO2 NP nanocomposite than before the application. The reuse application experiments showed that the Pb2+-MC/TiO2 NP nanocomposite might be a useful alternative material for blood fingerprint enhancement when applied on nonporous surfaces, eliminating secondary pollution.

Assessing the Tolerance Impact of Fungal Isolates against Lead and Zinc Heavy Metals under Controlled Conditions

Now a day’s cultivated lands are being polluted with heavy metals which is become very common issue in the country as well as across the globe due to increase in geologic and anthropogenic activity. Because of human activity, there is excess release of heavy metals like cadmium, copper, lead, nickel, zinc, and/are going on increasing up to alarming level which may significantly affects the crop yield and soil micro flora as well. Reports revealed that biological treatments, especially filamentous fungi are playing an important role in removal of heavy metals from the contaminated environment of the ecosystem. Hence, in present study we have isolated filamentous fungi viz., Trichoderma spp. and Aspergillus niger from contaminated soil with heavy metals with aim to find their tolerance properties towards selective heavy metals such as, Lead and Zinc. Findings of our study highlighted that Trichoderma spp. have greater ability to grow under varying Zinc and Lead concentration and shows greater tolerance limit of 0.98 at 5mM of Zinc concentration and 0.83 tolerance limits at 100 ppm lead concentration. Similarly, the fungi Aspergillus niger has ability to grow faster at high lead concentration and shows tolerance limit of 1.07 at 200 ppm of lead concentration. Thus, it is concluded that the filament fungi namely Trichoderma spp. and Aspergillus niger are efficient in removal of toxic heavy metals from the polluted soil. Hence, we can employ these fungi individually or in consortium as effective agents for bioremediation of the contaminated soil in order to crop cultivation and enhancing the yield of useful crop plants for supplying the demand of growing population.

Bioinspired Synthesis of Silver Nanoparticles for the Remediation of Toxic Pollutants and Enhanced Antibacterial Activity.

This research presents a novel and environmentally friendly approach for the synthesis of multifunctional nanobiocomposites for the efficient removal of toxic heavy metal and dye, as well as the disinfection of wastewater microorganisms. The nanobiocomposites (KAC-CS-AgNPs) were prepared by incorporating photochemically generated silver nanoparticles (AgNPs) within a chitosan (CS)-modified, high-surface-area activated carbon derived from kenaf (KAC), using a unique self-activation method. The even distribution of AgNPs was visible in the scanning electron microscopy images and a Fourier transform infra red study demonstrated major absorption peaks. The experimental results revealed that KA-CS-AgNPs exhibited exceptional adsorption efficiency for copper (Cu2+), lead (Pb2+), and Congo Red dye (CR), and showed potent antibacterial activity against Staphylococcus aureus and Escherichia coli. The maximum adsorption capacity (mg g-1) of KAC-CS-AgNPs was 71.5 for Cu2+, 72.3 for Pb2+, and 75.9 for CR, and the adsorption phenomena followed on the Freundlich and Langmuir isotherm models and the second-order kinetic model (R2 > 0.99). KAC-CS-AgNPs also exhibited excellent reusability of up to four consecutive cycles with minor losses in adsorption ability. The thermodynamic parameters indicated that the adsorption process was spontaneous and endothermic in nature. The bacterial inactivation tests demonstrated that KAC-CS-AgNPs had a strong bactericidal effect on both E. coli and S. aureus, with MIC calculated for E. coli and S. aureus as 32 µg mL-1 and 44 µg mL-1, respectively. The synthesized bioinspired nanocomposite KAC-CS-AgNPs could be an innovative solution for effective and sustainable wastewater treatment and has great potential for commercial applications.

Highly efficient adsorption of arsenite from aqueous by zirconia modified activated carbon

In the present study, activated carbon decorated with zirconia nanoparticle composite (ZrO2/AC) have been prepared using hydrothermal method and then utilized as an adsorbent for the removal of arsenite from aqueous solution. The composite is composed of highly agglomerated ZrO2 particles on AC surface. The high surface area of the synthesized adsorbent results in its high adsorption capacity toward arsenite. Adsorption isotherm and kinetic data of arsenite adsorption process can be well fitted to the Langmuir isotherm with maximum monolayer adsorption capacity of 64.00 mg.g-1. The experimental results suggest that the adsorption process of arsenite onto ZrO2/AC material involves the formation of both outer-sphere and inner-sphere complexes between arsenite and adsorbent. The high adsorption ability toward arsenite as well as the high recyclable nature of this material makes it a potential alternative material for the removal of toxic heavy metals from wastewater.