Removal Efficiency Of Heavy Metals Research Articles

Recyclable Mg-MOF-74@cellulose aerogel composites for efficient removal of heavy metals from wastewater

In this study, Mg-MOF-74, an environmentally friendly metal-organic framework material with non-toxic Mg elements as the framework centers, was loaded onto low-cost and green cellulose aerogels via an in-situ growth approach to construct the Mg-MOF-74@CA composite with a three-dimensional porous structure, overcoming the problems that Mg-MOF-74 nanoparticles tend to agglomerate and cannot be easily recovered. The removal performance of the synthesized Mg-MOF-74@CA composite towards Pb(II), Cd(II), and Cu(II) was evaluated by combining batch experiments, model fittings, and characterization analyses (SEM, XRD, FTIR, MIP, TG, and XPS). The results show that the porosity of Mg-MOF-74@CA is 84.447%. The removal of Pb(II), Cd(II), and Cu(II) by Mg-MOF-74@CA reach the equilibriums at about 5 h. And the removal of Pb(II), Cd(II), and Cu(II) by Mg-MOF-74@CA are strongly influenced by solution pH, while almost independent of ionic strength and humic acid (HA). The strong complexation of Pb(II), Cd(II), and Cu(II) with the surface sites of Mg-MOF-74@CA is the main removal mechanism. The maximum adsorption capacities of Mg-MOF-74@CA towards Pb(II), Cd(II), and Cu(II) at 298 K are 223.555, 160.033, and 74.349 mg/g, respectively. Interestingly, the selective binding order of Mg-MOF-74@CA for Pb(II), Cd(II), and Cu(II) is Cu(II)>Pb(II)>Cd(II). In summary, the Mg-MOF-74@CA composite has good application prospects in practical wastewater treatment.

New dithiocarbamate-based polymer (DTCP) as an additive to improve microporous polysulfone membrane efficiency in lead and dye removal

For fabricating a membrane with hydrophilic and complexing agent groups, a new dithiocarbamate-based polymer (DTCP) containing dithiocarbamate, thioamide, and ethereal oxygen groups was synthesized and blended in polysulfone (PSF) matrix with 1, 2, 5, and 10 wt% proportion. The membranes were produced by the nonsolvent induced phase separation method. For DTCP characterization, NMR, FTIR, TGA and GPC techniques were used. SEM images show that no morphological change can be seen even in 10 wt% blended membranes. AFM surface images show that the roughness of 5 and 10 wt% membranes extremely increased. The performance of the DTCP/PSF membranes were investigated in the separation of lead ions and Reactive Yellow 39 dye from the contaminated water. The outcomes indicated that by increasing the amount of DTCP up to 10 wt%, the pure water flux, bovine serum albumin flux, and the lead removal increased very efficiently compared to the bare one. Blending of more than 1 wt% DTCP, cause to removal of 99.6% lead ions. The water contact angle decreased by the adding of DTCP, caused to increase fouling resistance. The results of this research shows that the synthesized DTCP can be used as a good additive for improving membrane permeability, anti-fouling and especially heavy metal removal efficiency.

Biosorption of pollutants from chemically derived wastewater using Microcoleus sp.

Abstract Microcoleus sp. is a versatile microorganism widely available in the environment and easily culturable. Hence, there is a progressing demand for wastewater treatment using this novel biosorption medium. The design of such a treatment method may be defined as an optimisation problem of algal dose and hydraulic retention time for attaining an adequate removal efficiency of heavy metals (Cr6+, Ni2+, and Zn2+) and nutrients (PO43- and NO3-). Batch experiments on synthetic wastewater were conducted for algal doses varying from 0.5 to 25 g/L and hydraulic retention times from 1 to 7 days. Significant removal efficiencies of greater than 90% were observed for the heavy metals, 75% of PO43- removal, and no removal of NO3- was found under continuous daylight. The single-factor ANOVA test confirms the statistical significance of the varying parameters on the pollutant removal efficiency. Langmuir and Freundlich's adsorption isotherms indicate satisfactory adsorption of the contaminants about the separation factor and the adsorption intensity constant. The R2 > 0.67 and RMSE < 0.21 suggest a good fit of the modelled data. Following this, the study suggests that the use of Microcoleus sp. is a prospective bioremediation technique for industrial and municipal wastewater.

Removal of organic pollutants, heavy metals and trace elements from sewage using Phragmites australis (Cav.) Trin. ex Steud.

Potential removal of emerging organic pollutants, heavy metals and trace elements using the reed plant Phragmites australis (Cav.) Trin. ex Steud was evaluated in the year 2020. HPLC analysis showed that the removal efficiency of pyrene and dibutyl phthalate at the end of four-week experiments were 87.37 ± 4.95% and 83.67 ± 5.62%, respectively. Investigation of heavy metals through ICP-AES showed that the efficiency of heavy metal removal was in order of Ba > Zn > As > Cu > Al > Pb > Cd > Cr > Ag. Trace elements such as P, K and Na were removed as high as 70 % from the sewage. Analysis of Phragmites sp., indicated that the removed heavy metals from sewage was mostly found in roots and less translocated to the shoot system. Hence this model study could be extrapolated so that P. australis could serve as efficient biomitigator for the removal of emerging organic pollutants, heavy metals, and trace elements. Bangladesh J. Bot. 52(1): 9-15, 2023 (March)

Highly efficient removal of toxic As(V), Cd (II), and Pb(II) ions from water samples using MnFe2O4@SBA-15-(CH2)3-adenine as a recyclable bio-nanoadsorbent

Millions of people nowadays are exposed to highly toxic ions, including arsenic, cadmium, and lead, which all have detrimental effects on human health and cause irreparable damage to the nature and health of living species. It is, therefore, absolutely crucial to remove these toxic ions from ecosystems. Herein, a sponge-like bio-nanocomposite with a core-shell-shell structure consisting of magnetic MnFe2O4 nanoparticles (NPs) as core and mesoporous silica (SBA-15) functionalized with the nucleobase adenine (Ade) as a shell was synthesized to be applied for the adsorptive removal of toxic ions from aqueous media. The prepared material was characterized using various techniques, such as FTIR, XRD, TEM, VSM, and BET. Under optimum conditions, the MnFe2O4@SBA-15@(CH2)3-Ade removed As(V), Cd(II), and Pb(II) ions with greater than 96% efficiency. The kinetic and equilibrium data were satisfactorily described by the pseudo-second-order and the Redlich-Peterson models. The maximum adsorption capacities for As(V), Cd(II), and Pb(II) were calculated to be 21.99 mg g−1, 29.62 mg g−1, and 31.01 mg g−1, respectively. Also, the bio-nanocomposite showed ion removal efficiencies of over 95% during the seventh cycle of adsorption-desorption. Pb (II) ions had a stronger affinity for the active sites of the bio-nanoadsrobent when all of the studied systems (mono-, bi-, and multi-component) were compared. In addition, the practical application of the bio-nanocomposite for ion capture was evaluated in groundwater and industrial wastewater samples. Based on the findings of this study, the MnFe2O4@SBA-15@(CH2)3-Ade can be considered a promising adsorbent for the fast and efficient removal of heavy metals from water matrices.

Chitosan-based hollow nanofiber membranes with polyvinylpyrrolidone and polyvinyl alcohol for efficient removal and filtration of organic dyes and heavy metals

Due to their large specific surface area and numerous diffusion channels, hollow fibers are widely used in wastewater treatment. In this study, we successfully synthesized a chitosan (CS)/polyvinylpyrrolidone (PVP)/polyvinyl alcohol (PVA) hollow nanofiber membrane (CS/PVP/PVA-HNM) via coaxial electrospinning. This membrane demonstrated remarkable permeability and adsorption separation. Specifically, the CS/PVP/PVA-HNM had a pure water permeability of 4367.02 L·m−2·h−1·bar−1. The hollow electrospun nanofibrous membrane exhibited a continuous interlaced nanofibrous framework structure with the extraordinary advantages of high porosity and high permeability. The rejection ratios of CS/PVP/PVA-HNM for Cu2+, Ni2+, Cd2+, Pb2+, malachite green (MG), methylene blue (MB) and crystal violet (CV) were 96.91 %, 95.29 %, 87.50 %, 85.13 %, 88.21 %, 83.91 % and 71.99 %, and the maximum adsorption capacities were 106.72, 97.46, 88.10, 87.81, 53.45, 41.43, and 30.97 mg·g−1, respectively. This work demonstrates a strategy for the synthesis of hollow nanofibers, which provides a novel concept for the design and fabrication of highly efficient adsorption and separation membranes.

Salinity and temperature influence removal levels of heavy metals and chloride from water by wetland plants

Stormwater with low temperatures and elevated salinity, common in areas where deicing salt is used, might affect the removal of heavy metals by plants in stormwater treatment systems such as floating treatment wetlands. This short-term study evaluated the effects of combinations of temperature (5, 15, and 25 °C) and salinity (0, 100, and 1000 mg NaCl L−1) on the removal of Cd, Cu, Pb, and Zn (1.2, 68.5, 78.4, and 559 μg L−1) and Cl− (0, 60, and 600 mg Cl− L−1) by Carex pseudocyperus, C. riparia, and Phalaris arundinacea. These species had previously been identified as suitable candidates for floating treatment wetland applications. The study found high removal capacity in all treatment combinations, especially for Pb and Cu. However, low temperatures decreased the removal of all heavy metals, and increased salinity decreased the removal of Cd and Pb but had no effect on the removal of Zn or Cu. No interactions were found between the effects of salinity and of temperature. Carex pseudocyperus best removed Cu and Pb, whereas P. arundinacea best removed Cd, Zu, and Cl−. The removal efficacy for metals was generally high, with elevated salinity and low temperatures having small impacts. The findings indicate that efficient heavy metal removal can also be expected in cold saline waters if the right plant species are used.

Enhanced electrokinetic remediation by magnetic induction for the treatment of co-contaminated soil

The electroplating industry site is an important reservoir of per- and poly-fluoroalkyl substances (PFASs) and heavy metals. In this work, a novel electrokinetic in-situ chemical oxidation system was established to restore an actual soil co-contaminated with high concentrations of heavy metals (Cr, Cu, Zn and Ni) and PFASs. Potassium persulfate (PS, K2S2O8) and industrial waste steel slag were used as the oxidant and activator, respectively. The steel slag was evenly added in the soil, while PS was dosed in the cathode chamber. Citric acid fermentation broth produced by Aspergillus niger was added in the anode chamber to act as the metal chelator. A periodic alternating magnetic field was employed to enhance the catalytic performance of steel slag for PS. After 15-day treatment, 86.7% of PFASs and 87.2% of heavy metals were removed without PFASs accumulation in the electrolyte, with a defluorination percentage of 79.2%. The remediated soil had no phytotoxicity for wheat seed growth based on 7-day cultivation results. The quality of remediated soil could reach the national Class II criteria for residential use. Electron paramagnetic resonance spectroscopy analysis demonstrated that SO4•– and •OH were the major oxidative radicals responsible for PFASs degradation. Adding steel slag in the soil performed better than that in the cathode chamber based on pollutant removal and alleviating soil acidification. Magnetic induction could enhance PS activation by promote the corrosion of steel slag and thermal activation, thus increasing electrical current and electroosmotic flow, enhancing the transport of citric acid and PS, significantly improving the removal efficiency of heavy metals and PFASs.

Potential Use of Two Forest Species (Salix alba and Casuarina glauca) in the Rhizofiltration of Heavy-Metal-Contaminated Industrial Wastewater

The discharge of raw industrial wastewater (IWW) into ecosystems is a major environmental problem that adversely affects water quality, soil physicochemical properties, the food chain and, therefore, human health. Injection of treated IWW into irrigation and “fertigation” systems is an ecological, sustainable and economical approach for its appropriate disposal. Seedlings of two forest species (Salix alba, Casuarina glauca) were grown hydroponically and subjected to 25% diluted IWW and control (tap water) treatments for 35 days. Morphological and physiological traits were evaluated, including leaf symptoms, stem and root dry masses, leaf water potential, relative water content, chlorophyll content, photosystem II efficiency, hydrogen peroxide, thiobarbituric acid reactive substances, bioaccumulation and translocation factor estimates and removal efficiency for various heavy metals. Application of 25% IWW stress affected many aspects of plant morphology: chlorosis and necrosis in leaves, epinasty, leaf curling, early leaf senescence and root browning. In both species, the 25% IWW treatment reduced leaf, stem and root dry masses relative to controls. S. alba exhibited greater removal capacity for heavy metal ions and could be effective as a remediator of toxic-metal-polluted industrial effluent water.

Efficient removal of heavy metals from aqueous solutions by Mg/Fe bimetallic oxide-modified biochar: Experiments and DFT investigations

Mg/Fe bimetallic oxide-modified biochar (Fe/Mg-BC) derived from Eupatorium adenophorum was prepared by the co-pyrolysis of magnesium nitrate and ferric chloride for Pb(II) and Cd(II) removal from wastewater. The physicochemical properties of the Fe/Mg-BC were analyzed by several characterization methods such as XRD, XPS, SEM and FTIR. Pb(II) and Cd(II) adsorption amounts of Fe/Mg-BC in monometallic systems is larger than those in bimetallic systems owing to competitive adsorption. The adsorption mechanism analysis indicated that ion exchange and mineral precipitation were responsible for Pb(II) and Cd(II) adsorption. The overlap of electron clouds and orbits between MgO and Pb(II) is denser than that of Cd(II), indicating that Fe/Mg-BC has a stronger affinity for Pb(II) than for Cd(II) based on density functional theory calculations. The reusability result indicates that Fe/Mg-BC shows excellent Pb(II) and Cd(II) adsorption performance. Fe/Mg-BC presented remarkable adsorption capability, excellent recoverability, and high throughput, indicating its potential application in the treatment of wastewater containing heavy metals.

Removal of mixed contaminants from landfill leachate-contaminated soil by flushing with bio-surfactant: laboratory column tests.

Landfill leachate-contaminated soil is widespread all over the world. In order to study the removal of mixed contaminants from landfill leachate-contaminated soil by flushing with bio-surfactant, soil column test was conducted to select an optimum concentration of bio-surfactant saponin (SAP) at first. Then, the removal efficiencies of organic contaminants, ammonia nitrogen, and heavy metals from landfill leachate-contaminated soil by flushing with SAP were studied. At last, the toxicity of contaminated soil before and after flushing was estimated by sequential extraction of heavy metals and plant growth test. The test results showed that the SAP solution with the concentration of 2.5 CMC could effectively remove the mixed contaminants from soil and would not introduce excessive pollutants of SAP in soil. Specifically, the removal efficiencies of organic contaminant and ammonia nitrogen were 47.01% and 90.42%, respectively. And the removal efficiencies of Cu, Zn, and Cd were 29.42%, 22.55%, and 17.68%, respectively. During flushing, hydrophobic organic compounds as well as physisorption and ion-exchange ammonia nitrogen in soil were removed by the solubilization effect of SAP, and heavy metals were removed by the chelation of SAP. After flushing with SAP, the reduced partition index (IR) value of Cu and Cd increased, and the mobility index (MF) value of Cu decreased. In addition, flushing with SAP reduced the plant toxicity of contaminated soil, and the residual SAP in soil promoted the plant growth. Therefore, flushing with SAP offered great potentials in remediating the landfill leachate-contaminated soil.

Montmorillonite-mediated electron distribution of zirconium phosphate for accelerating remediation of cadmium-contaminated water and soil

Rapid and efficient remediation of heavy metal-contaminated water and soil bodies has been a hot topic in ecological remediation. However, designing and synthesizing green remediation materials with fast kinetics and high adsorption capacity is still challenging. In this study, a novel heavy metal remediation material (Mt@ZrP) has been prepared using montmorillonite to induce the structural rearrangement of zirconium phosphate (ZrP). The results showed that montmorillonite could mediate the external electron distribution of ZrP, thus increasing its O 1 s binding energy. Distinct from the electrostatic adsorption of bare ZrP, Mt.@ZrP with higher orbital binding energy led to an extra adsorption mode with internal spherical coordination. Such characteristics dramatically shortened the adsorption equilibrium time (23 min) and enhanced the adsorption capacity (275.6 mg/g-ZrP) of Mt.@ZrP for Cd removal in comparison to those of bare ZrP (220 min, 196.1 mg/g-ZrP). As for soil remediation, Mt.@ZrP presented a faster Cd removal rate than bare ZrP. The residual fraction increased from 22.03% (control) to 28.47% (Mt@ZrP, 1 wt%) and 37.54% (Mt@ZrP, 3 wt%), which significantly decreased the biological efficacy of Cd in the soil. These findings could provide a novel strategy for the design and synthesis of excellent remediation materials for the rapid and efficient removal of heavy metals in water and soil.

The deconstruction and recombination of endogenous active units of carbon@chitosan@montmorillonite nanosheet microsphere adsorbent caused by cadmium and copper cations benefit for high adsorption performance.

The highly efficient removal of heavy metals is one of the important factors to evaluate adsorbents. In our study, carbon@chitosan@montmorillonite nanosheet (C@CS@MTN) was successfully prepared via layer-by-layer assembly for the removal of Cu2+ and Cd2+ from solution. High-intensity ultrasound peeling technology was used to release Si-O tetrahedron and Al-O octahedron from montmorillonite in order to exert their optimal adsorption potential. Fourier transform infrared spectroscopy, an X-ray diffractometer, BET surface area measurement, and the inductively coupled plasma emission spectrometry were adopted to investigate the morphology, functional groups, and adsorption capacity of C@CS@MTN. Batch experiment results indicated that both Cu2+ and Cd2+ were effectively removed from solution with the range of pH from 2 to 6. The removal ratio of Cu2+ and Cd2+ onto C@CS@MTN increased with the rise of reaction temperature and their maximum adsorption capacities reached 1108.8mg·g-1 and 237.4mg·g-1, respectively, under the condition of the reaction temperature 40°C, the reaction time 4h, and the pH = 6. The molecular simulation calculation indicated that there was an obvious electron transfer between Si-O tetrahedron and metal cations, but not for Al-O octahedron. In comparison to Al-O octahedron, the bonding of Cu-O and Cd-O caused the Si-O bond to be broken, resulting in the deconstruction of Si-O tetrahedron and their recombination via the junction of O atoms. It was exactly the deconstruction and recombination of endogenous active units that provide more sites for metal ion adsorption.

Recovery of Collagen/Gelatin from Fish Waste with Carbon Dioxide as a Green Solvent: An Optimization and Characterization

Fish processing produces large amounts of fish waste. Instead of disposing of it, it is wiser to recover the valuable resource for high-value-added products. Our study proposed a process using carbon dioxide-acidified water as a green solvent under supercritical conditions to successfully recover collagen/gelatin from the skin and bone of striped catfish. The optimum extraction conditions were obtained at 75 bar, 37 °C, and 24 h. The yields from the dry skin and bone mass were around 37% and 8%, respectively. The extracted products were characterized by Fourier-transformed infrared spectroscopy to study the functional groups, scanning electron microscopy to evaluate the morphology, sodium dodecyl-sulfate polyacrylamide gel electrophoresis to study the protein pattern, UV–vis analysis to measure the absorption peak, and thermal gravimetric analysis to determine the denaturation temperature. The results show the viability of the proposed method on an industrial scale. The characteristics of the extracted product show promising results and potential for being developed further in many applications such as biomaterial engineering in healthcare or natural polymer-based absorbent material for efficient removal of heavy metals from water and wastewater.

Polyethylene glycol functionalized Fe3O4@MIL-101(Cr) for the efficient removal of heavy metals from Ligusticum chuanxiong Hort

In recent years, the quality and safety issues of Chinese medicinal herbs have received great attention worldwide. Thereinto, heavy metal contamination has been one of the most serious concerns. Compared to the wide research in the analysis of heavy metals in medicinal herbs, the studies on the removal of heavy metals are relatively limited. In this study, polyethylene glycol functionalized Fe3O4@MIL-101(Cr) (Fe3O4@MIL-101(Cr)@PEG) was designed and synthesized to remove heavy metals from the decoction of Ligusticum chuanxiong Hort. The in-house fabricated Fe3O4@MIL-101(Cr)@PEG was characterized by a porous structure and a large specific surface area. Then, the efficiency of the material for the removal of five heavy metals was tested under optimal adsorption conditions. Meanwhile, the content of Senkyunolide A, Senkyunolide I, and Ferulic acid, the solid content, and the HPLC fingerprints similarity were used as the quality monitoring indicators of Ligusticum chuanxiong Hort decoction before and after the heavy metal removal. Results showed that the magnetic nanomaterial had excellent removal efficiency for As5+ (81.4 %), Cd2+ (88.19 %), and Pb2+ (83.79 %) and certain removal efficiency for Ni2+ (51.59 %) and Zn2+ (55.4 %) under the spiked concentration of 50 μg/mL. The content of Senkyunolide A, Senkyunolide I, and Ferulic acid were decreased by less than 8.00 % after the removal of heavy metals. Besides, the loss rate of solid content was only 0.18 %, and the fingerprints similarity was over 99.9 %. The results indicated that Fe3O4@MIL-101(Cr)@PEG could efficiently and selectively remove heavy metals from Ligusticum chuanxiong Hort without affecting its effective components. Due to the advantages of low-cost, simple manipulation, and good efficiency, the material can be recommended for heavy metals removal from the aqueous solutions of medicinal herbs, providing a new and promising application for the removal of exogenous contaminants in medicinal herbs.

Cu(II) and Cr(VI) Removal in Tandem with Electricity Generation via Dual-Chamber Microbial Fuel Cells

Microbial fuel cells (MFCs) have shown great advantages in electricity production, heavy metal removal, and energy recovery. However, the impact and mechanism of conflicting effects of numerous electron acceptors on heavy metal removal remain unknown. The effects of different initial heavy metal concentrations, cathodic dissolved oxygen, and electrode materials on the electricity generation and heavy metal removal efficiencies of Cu(II) and Cr(VI) were investigated in this study. When the initial concentration of Cr(VI) increased from 10 mg/L to 150 mg/L, the maximum voltage, coulomb efficiency, and maximum power density declined from 99 to 44 mV, 28.63% to 18.97%, and 14.29 to 0.62 mW/m2, and the removal efficiencies of Cu(II) and Cr(VI) decreased dramatically from 98.34% and 99.92% to 67.09% and 37.06%, respectively. Under anaerobic cathodic conditions, the removal efficiency and removal rate of Cu(II) and Cr(VI) were lower than those under aerobic conditions. When the cathode electrode was titanium sheet and graphite plate, the coulomb efficiency and maximum power density increased to 38.18%, 50.71%, 33.95 mW/m2, and 62.23 mW/m2. The removal efficiency and removal rates of Cu(II) and Cr(VI) were significantly increased to 98.09%, 86.13%, and 0.47, 0.50 mg/(L h) with a graphite plate, respectively. The pH of the cathode varied considerably greater as the MFC current increased. Cu(II) and Cr(VI) were removed and reduced to elemental Cu, Cu2O, and its oxides as well as Cr(OH)3 and Cr2O3 precipitates on the cathode electrode by cathodic bioelectrochemical reduction.

Simultaneous removal of multiple heavy metals using single chamber microbial electrolysis cells with biocathode in the micro-aerobic environment

The simultaneous and efficient removal of various heavy metals from wastewater to satisfy the requirements of zero discharge has been a research hotspot and difficult point. In the laboratory scale (0.5 L), the biocathode microbial electrolytic cells (BCMECs) were constructed with the pre-screened heavy metal-tolerant electroactive bacterial, mainly of the Sphingomonas, Azospira and Cupriavidus. The BCMECs system showed a more satisfactory removal effect for multiple heavy metals and organic pollutants. At the auxiliary voltage of 0.9 V and initial concentration of 20 mg L−1, the removal efficiency of Cu, Pb, Zn, Cd and COD were 98.76 ± 0.32%, 98.01 ± 0.76%, 73.58 ± 4.83%, 84.39 ± 5.95%, 77.55 ± 1.51%, respectively. It was found by various characterization techniques (CV, EIS, XPS et al.) that the constructed biocathode has the function of electrocatalytic reduction of heavy metal ions in a micro-aerobic, film-free environment. The positive shift (0.030–0.229 V) of the initial potential for heavy metal reduction and the absence of a significant increase (＜ 10 Ω) in the interfacial resistance indicated a reduction in the total free energy of the reduction reaction, which promotes the reaction and improves the efficiency of heavy metal removal. Bacterial community analysis revealed that the Proteobacteria has been dominant in different heavy metal environments. With the increase of heavy metal concentration, Sphingomonas, Azospira and Cupriavidus showed stronger tolerance and became the dominant genus. This study emphasized the important performance of biocathodes and the effective treatment of heavy metal wastewaters by BCMECs and provided a reasonable way for industrial and mining enterprises to innovate the water treatment process.

Multifunctional cobalt oxide nanocomposites for efficient removal of heavy metals from aqueous solutions

In this study, co-precipitation synthesis of natural clay (NC) with Co3O4 nanoparticles (NPs) is carried out to elaborate the super NC@Co3O4 nanocomposites with admirable salinity confrontation, environmental stability and reusability, to eliminate heavy metal pollution such as toxic Pb(II) and Cd(II) ions. The advantages of using the NC@Co3O4 adsorbent are easy synthesis and biocompatibility. In addition, NC@Co3O4 can keep an excellent adsorption capacity by taking into account various environmental parameters such as the pH solution, NC@Co3O4 dose, adsorption process time and the initial heavy metals concentration. Furthermore, FTIR, XRD, TGA, SEM-EDS, TEM and AFM analyses were performed to confirm NC@Co3O4 nanocomposites synthesis and characterisation. The adsorption efficiencies of Pb(II) and Cd(II) ions by NC@Co3O4 nanocomposites were demonstrated to be up to 86.89% and 82.06% respectively. Regarding the adsorption from water onto the NC@Co3O4 nanocomposites, kinetics data were well fitted with PSO kinetic model, whereas a good agreement was found between the equilibrium adsorption and theoretical Langmuir isotherm model leading to maximum adsorption capacities of 55.24 and 52.91 mg/g, for Pb(II) and Cd(II) respectively. Monte Carlo (MC) simulations confirmed the spontaneous of this adsorption based on the negative values of Eads. The MC simulations were performed to highlight the interactions occurring between heavy metal ions and the surface of NC@Co3O4 nanocomposites, these were well correlated with the experimental results. Overall the study showed that NC@Co3O4 nanoadsorbents have strongly versatile applications and are well designed for pollutant removal from wastewater due to their unique adsorptive properties.

Interfacial chemical bond modulated Z-scheme mechanism in In2−xS3/Cd1+xIn2−xS4 heterojunction for enhanced photocatalytic CO2 reduction and wastewater treatment

An interfacial CdS bond modulated hierarchical Z-scheme heterostructure composed by indium vacancies-rich In2-xS3 and Cd-rich Cd1+xIn2-xS4 (In2-xS3/Cd1+xIn2-xS4) is rationally designed and fabricated by using MIL-68 (In) as precursor and template, and used for efficient photocatalytic wastewater treatment and CO2 reduction. The in-situ ion-exchange derived CdS bond at the heterointerface induced the Z-scheme charge transfer mechanism in hierarchical In2-xS3/Cd1+xIn2-xS4 photocatalyst, which is verified by the X-ray photoelectron spectroscopy, electron paramagnetic resonance and density functional theory calculations. Moreover, the hierarchical ultrathin and loose two-dimensional nanosheet structure is conducive to expose more active sites and adsorb more reactants. By integrating the efficient adsorption capacity and Z-scheme mechanism, the In2-xS3/Cd1+xIn2-xS4 photocatalyst shows superior photocatalytic CO2 reduction activity and high removal efficiency of dyes and heavy metal. For example, under visible light illumination, it removed almost 100 % of various dyes within 10 min operation, and reduced 100 % Cr(VI) within 1 h, and it also manifested state-of-the-art production rates of 132.5 and 392.1 μmol h−1 g−1 for CH4 and CO, respectively, in reducing CO2 without co-catalyst. A useful inspiration on purposive modulating Z-scheme charge transfer by atomic-level interface engineering was proposed to significantly promote the photocatalytic performance.

Efficient Removal of Heavy Metals from Contaminated Sunflower Straw by an Acid-Assisted Hydrothermal Process.

The removal of heavy metals is crucial to the utilization of contaminated biomass resources. In this study, we report an efficient process of hydrothermal conversion (HTC) of sunflower straw (Helianthus annuus L.) to remove heavy metals. The effect of different HTC temperatures and concentrations of HCl additives on heavy metal removal efficiency was investigated. The results revealed that increasing the temperature or concentration of HCl promoted the transfer of heavy metals from hydrochar to liquid products during HTC. The heavy metals removed to the liquid products included up to 99% of Zn and Cd, 94% of Cu, and 87% of Pb after hydrothermal conversion with a temperature of 200 °C and HCl 2%. The species of heavy metals in hydrochars converted from unstable to stable with an increase in temperature from 160 °C to 280 °C. The stable fractions of heavy metals in the acidic condition decreased as the acid concentration increased. This aligns well with the high transfer efficiency of heavy metals from the solid phase to the liquid phase under acidic conditions. The FTIR indicated that the carboxy and hydroxy groups decreased significantly as the temperature increased and the concentration of HCl increased, which promoted the degradation of sunflower straw. A scan electron microscope showed that the deepening of the destruction of the initial microstructure promotes the transfer of heavy metals from hydrochars to liquid phase products. This acid-assisted hydrothermal process is an efficient method to treat biomass containing heavy metals.