Heavy Metals In Wastewater Research Articles

Sorption of chromium from aqueous solutions using Fucus vesiculosus algae biosorbent

The presence of heavy metals in wastewater is an environmental concern and the current treatment procedures are very expensive so it is necessary to find effective and inexpensive biosorbents. In this study, Fucus vesiculosus was used as a biosorbent for the biosorption of Cr(III) ions from the aqueous solutions. Biosorption parameters, such as pH, adsorbent dose, contact time, and initial concentrations of Cr(III) had the most impact on the sorption process. The required pH value for sorption was 5, the biosorbent dose was 4.0 g/L, the contact time was seen to occur after 90 min, and the Cr(III) removal decreased from 98.9 to 92%. The maximum biosorption capacity of chromium was 14.12 mg/g. FTIR analysis of Fucus vesiculosus biomass before the sorption process contains carboxyl, amino, hydroxyl, alkyne, and carbonyl groups, and according to the analysis after the sorption process, it was found that Cr(III) metal ions were incorporated within the sorbent during the interaction with (=C–H) active functional groups. The biosorption data were found to be perfectly suited by Langmuir equilibrium isotherm model. According to the results of this study, Fucus vesiculosus is an effective biosorbent for the removal of Cr(III) from aqueous solutions.

Study on the preparation of Nano-Fe3O4 by steel pickling waste liquor and its effective removal of Cr (VI) from wastewater

In order to comprehensively treat and utilize steel pickling waste liquor (SPWL), this study used SPWL as raw material to prepare two different crystalline forms of Nano-Fe3O4 by co-precipitation and precipitation-oxidation methods, and investigated their removal effect on Cr(VI) in wastewater. The two kinds of Nano-Fe3O4 were characterized using SEM, XRD, and VSM, and the results showed that the Nano-Fe3O4 synthesized by the co-precipitation method has better properties. The two kinds of Nano-Fe3O4 were used to remove Cr(VI) in wastewater, the adsorption capacity could reach 38.38 mg/g and 15.83 mg/g, respectively. Five adsorption kinetic models and five isothermal adsorption models were used to study the adsorption mechanism of Fe3O4 on Cr(VI). The adsorption process of Cr(VI) by Nano-Fe3O4 was explained well using the pseudo-second-order and Freundlich isotherm model, and the results showed that the adsorption process mainly involved physical and chemical adsorption. Through the characterization analysis before and after the reaction, the removal mechanism of Cr(VI) by Nano-Fe3O4 prepared from SPWL is mainly attributed to electrostatic adsorption and reduction reaction. According to the market survey and analysis, the production cost is reduced by at least 58.33 % compared to that of Nano-Fe3O4 prepared using analytical purity in the market. Therefore, the preparation of Nano-Fe3O4 by steel pickling waste liquor provides an economical and effective way to remove heavy metal ions in wastewater.

Efficient removal and stepwise recovery of various heavy metals from water by using calcium carbonate with different activity

Heavy metals in wastewater have caused serious environmental contamination in the world. However, a key challenge with the most effective solution through chemical precipitation is the high pH of in the effluent by the use of lime. Herein, we propose a strategy using highly active calcium carbonate (HACC) for enhancing its slow-release activity, which efficiently removes heavy metal contamination while avoiding high pH of the effluent. The HACC demonstrate a removal of more than 99 % for Cd(II), Cu(II), Zn(II) and Pb(II) from the composite contaminated water within 50 min, while maintaining the pH of the effluent close to neutral. In addition, mechanistic analyses unveil that the free heavy metals in different solutions combine with OH– and CO32– released from HACC in different precipitation behaviors to form their respective precipitates, thereby discovering the mechanism of regulating the precipitation rates of different heavy metals by controlling the activity of calcium carbonate. Based on it, the stepwise recovery of heavy metals was realized by adjusting the calcium carbonates with different activity. The present work provides guidance for gentle and efficient removal of heavy metal pollution in water bodies and inspires the future development of recovery of heavy metals.

Growth behavior of heavy metal sulfide particles: A comparison between gas-liquid and liquid-liquid sulfidation

Sulfide precipitation is an effective method for treating acidic heavy metal wastewater. However, the process often generates tiny particles with poor settling performance. The factors and mechanisms influencing particle size and settling performance remain unclear. In this study, the growth behavior of CuS particles generated by two sulfide precipitation methods, gas-liquid and liquid-liquid sulfidation, was investigated. The effects of acidity, sulfur-to-copper molar ratio, and temperature on particle size were analyzed. The results showed that increasing the temperature had an adverse effect on CuS particle growth. Additionally, we found that acidity and sulfur-to-copper molar ratio had a more significant impact on particle growth in the liquid-liquid sulfidation system than in the gas-liquid sulfidation system. Based on supersaturation calculations and XPS analysis, it is found that particle growth in gas-liquid sulfidation systems is mainly influenced by supersaturation, while particle growth in liquid-liquid sulfidation systems is mainly affected by surface charge. This study provides valuable insights into the factors that influence particle growth in sulfide precipitation and can inform the development of strategies to improve the effective precipitation of sulfide nanoparticles in acidic wastewater.

MXene@polydopamine/oxidized sodium alginate modified collagen composite aerogel as sustainable bio-adsorbent for heavy metal ion adsorption and solar driven water evaporation

The design of an environmentally friendly bio-adsorbent for the removal of heavy metal ions from aqueous media is a sustainable strategy to ensure water safety. Herein, a three-dimensional macroscopic aerogel with photothermal conversion and heavy metal wastewater treatment capability was designed using leather collagen, MXene@polydopamine and oxidized sodium alginate as raw materials, named as MPAC composite aerogel. The applicability of the developed MPAC composite aerogel in water evaporation and heavy metal wastewater treatment was studied. MPAC composite aerogel had good Cr(VI) adsorption capacity. This article focused on the study of adsorption kinetics, isotherms and thermodynamics. The adsorption equilibrium time of MPAC composite aerogel was 60 min, and the equilibrium adsorption capacity of MPAC composite aerogel for Cr(VI) reached 80.73, 100.80 and 112.86 mg/g when the initial Cr(VI) concentration was 30, 70 and 100 mg/L, respectively. The adsorption process of Cr(VI) by MPAC composite aerogel conformed to the two-level dynamics model and the Freundlich adsorption isotherm model, and was a spontaneous endothermic reaction. Additionally, the composite aerogel had good solar-driven water evaporation ability and could enhance the water evaporation rate of Cr(VI) solution. Furthermore, the MPAC composite aerogel had high adsorption performance for Cr(VI) under solar illumination conditions. This new aerogel has the advantages of low cost, environmental friendliness, strong adsorption capacity and photothermal conversion performance and is a promising heavy metal ion adsorbent.

Intercalation of GO-Ag nanoparticles in cellulose acetate nanofiltration mixed matrix membrane for efficient removal of chromium and cobalt ions from wastewater

Cellulose acetate (CA)/Polyethylene glycol (PEG) blended composite nanofiltration (NF) membrane encompassing graphene oxide-silver (GO-Ag) nanoparticles (NPs) has been successfully synthesized by dissolution casting techniques. The effect of different NP loadings on membrane morphology, surface roughness, hydrophilicity surface charge and permeation flux were evaluated. Owing to Donnon exclusion, steric hindrance, and solution diffusion mechanism, the synthesized modified membranes exhibited excellent rejection rates in the order of Co (II) (99 %) > Cr (VI) (91 %). Furthermore, pure water flux (PWF) of the modified membrane was obtained 660.56 L/m2h which is 78.45 % greater than pristine membrane. Due to its high surface hydrophilicity, surface roughness, and porosity, modified membrane exhibited good antifouling characteristics. The results indicated that the intercalation of GO-Ag NPs with a loading ratio of 0.8 wt% leads to the optimum membrane for Cr (VI) and Co (II) removal. The present work demonstrates the potential application of GO-Ag/CA modified NF mixed matrix membrane for serving as a promising platform for eliminating heavy metal ions in wastewater.

The effect of irrigation with magnetized wastewater on soil heavy metals, water productivity and heavy metals in aerial parts and grains of maize

Rising population strains food resources; reusing wastewater increases but brings microbial and heavy metal pollution, impacting nature and human health. Among environmental pollutants, heavy metals in wastewater are a major concern. Using magnetized water is a method to improve water and soil quality. The aim of this research is to investigate the effect of using treated magnetized wastewater on the chemical properties and tracking of heavy metals in the soil, performance and yield components, water efficiency, and absorption of heavy metals by maize plant. Irrigation treatments consisted of various water and wastewater blending ratios under both magnetic and non-magnetic field application conditions. The results showed that the effect of irrigation water and mixing of water and wastewater on electrical conductivity, soil salts and heavy metals in different depths were significant at 1% probability level. On average, irrigation with magnetized wastewater caused a significant increase in grain yield (9.8%) and biological yield of maize (10.63%) compared to non-magnetized wastewater treatment. Irrigation with magnetized wastewater caused a significant increase in biological (10.92%) and physical (10.13%) productivities compared to non-magnetized wastewater treatment. With applying a magnetic field resulted in a reduction of 17.99%, 23.25%, 17.86%, and 17.12% in the concentration of lead, cadmium, zinc, and nickel in the aerial parts of the plant, respectively, compared to the non-magnetized water treatment. Magnetized water increases the water use efficiency of maize and irrigation management with this technology can be useful in more effective and economical use of limited water resources.

Deep-sea microorganisms-driven V5+ and Cd2+ removal from vanadium smelting wastewater: Bacterial screening, performance and mechanism

The disorderly discharge of industrial wastewater containing heavy metals has caused serious water pollution and ecological environmental risks, ultimately threatening human life and health. Biological treatment methods have obvious advantages, but the existing microorganisms exhibit issues such as poor resistance, adaptability, colonization ability, and low activity. However, a wide variety of microorganisms in deep-sea hydrothermal vent areas are tolerant to heavy metals, possessing the potential for efficient treatment of heavy metal wastewater. Based on this, the study obtained a group of deep-sea microbial communities dominated by Burkholderia-Caballeronia-Paraburkholderia through shake flask experiments from the sediments of deep-sea hydrothermal vents, which can simultaneously achieve the synchronous removal of vanadium and cadmium heavy metals through bioreduction, biosorption, and biomineralization. Through SEM-EDS, XRD, XPS, and FT-IR analyses, it was found that V(V) was reduced to V(IV) through a reduction process and subsequently precipitated. Glucose oxidation accelerated this process. Cd(II) underwent biomineralization to form precipitates such as cadmium hydroxide and cadmium carbonate. Functional groups on the microbial cell surface, such as -CH2, C=O, N-H, -COOH, phosphate groups, amino groups, and M-O moieties, participated in the bioadsorption processes of V(V) and Cd(II) heavy metals. Under optimal conditions, namely a temperature of 40 °C, pH value of 7.5, inoculation amount of 10%, salinity of 4%, COD concentration of 600 mg/L, V5+ concentration of 300 mg/L, and Cd2+ concentration of 40 mg/L, the OD600 can reach its highest at 72 h, with the removal efficiency of V5+, Cd2+, and COD in simulated vanadium smelting wastewater reaching 86.32%, 59.13%, and 61.63%, respectively. This study provides theoretical insights and practical evidence for understanding the dynamic changes in microbial community structure under heavy metal stress, as well as the resistance mechanisms of microbial treatment of industrial heavy metal wastewater.

Facile fabrication of chitosan/bone/bamboo biochar beads for simultaneous removal of co-existing Cr(VI) and bisphenol a from water

Heavy metal Cr(VI) and organic BPA have posed harmful risks to human health, aquatic organisms and the ecosystem. In this work, Chitosan/bone/bamboo biochar beads (CS-AMCM) were synthesized by co-pyrolysis and in situ precipitation method. These microbeads featured a particle size of approximately 1 ± 0.2 mm and were rich in oxygen/nitrogen functional groups. CS-AMCM was characterized using XRD, Zeta potential, FTIR, etc. Experiments showed that adsorption processes of CS-AMCM on Cr(VI) and BPA fitted well to Langmuir model, with theoretical maximum capacities of 343.61 mg/g and 140.30 mg/g, respectively. Pore filling, electrostatic attraction, redox, complexation and ion exchange were the main mechanisms for Cr(VI), whereas for BPA, the intermolecular force (hydrogen bond) and pore filling were involved. CS-AMCM with adsorbed Cr(VI) demonstrated effective activation in producing ·OH and ·O2 from H2O2, which degraded BPA and Cr(VI) with the removal rates of 99.2% and 98.2%, respectively. CS-AMCM offers the advantages of low-cost, large adsorption capacity, high catalytic degradation efficiency, and favorable recycling in treating Cr(VI) and BPA mixed wastewater, which shows great potential in treating heavy metal and organic matter mixed pollution wastewater.

Construction of a novel poly(amide-ester) thin film composite hollow fiber nanofiltration membrane with high water permeance

Highly permeable hollow fiber (HF) nanofiltration (NF) membrane is strongly desired since it could achieve efficient desalination with much less energy consumption. In this study, we used 4,4′,4′′-trihydroxytriphenylmethane (TP) as an aqueous co-monomer with piperazine (PIP) to react with trimesoyl chloride (TMC) to prepare a new internally pressurized poly(amide-ester) HF NF membrane. With the incorporation of TP molecules, the synthesized poly(amide-ester) separation layer achieved larger pore size and better hydrophilicity, giving the HF NF membrane excellent water permeance. Under optimum conditions, the HF NF membrane has a water permeance of 151 L m−2 h−1 MPa−1, which is 50 % higher than that of the control HF NF membrane, while maintaining a Na2SO4 rejection of 97.5 %. Moreover, it displays excellent desalination performance towards heavy metal salt solutions and high salinity solutions. It also maintains excellent desalination performance during a long-time filtration experiment, which indicates its good durability performance. In summary, this new poly(amide-ester) HF NF membrane shows good promise for the treatment of heavy metal and high-salinity wastewaters.

Synthesis and characterization of a new multifunctional aliphatic poly(amic acid): An efficient polymeric adsorbent for removing the heavy metal ions

The heavy-metal ions in wastewater have attracted intense attention due to environmental issues, including their toxicity, bioaccumulation tendency, and persistency in nature. Despite other strategies for heavy metal removal from wastewater, adsorption is one of the most promising methods, owing to its simplicity and efficiency. To conserve the carboxyl and amine functional groups and prevent amidation reaction, a new aliphatic tertiary poly(amic acid) with linear and cyclic spacers was synthesized via the catalyst-free process. The ring opening of ethylenediaminetetraacetic acid dianhydride (EDTADA) by piperazine, a bifunctional cyclic secondary diamine, was conducted in a polar solvent (DMF) in a nitrogen atmosphere for 3 h. The characterization was conducted by FTIR and NMR, and their morphology and elemental composition were investigated by field emission scanning electron microscopy and energy dispersive X-ray (FESEM-EDX). As-synthesized aliphatic tertiary poly(amic acid) could be separated as a white powder with an O/N ratio of 0.93 ± 0.03 and morphology of woven fiber. The white powder showed an average molecular weight (M̅w) of ∼12,000 and a polydispersity index (PDI) of 1.52 ± 0.05. In addition, the poly(amic acid) TGA/DTA analysis showed a high thermal stability with stepwise degradation with the onset of 346 °C. The poly(amic acid) DSC profile displayed a high glass transition at 124 °C. The Brunauer–Emmett–Teller (BET) surface area and pore volume were determined to be 146.05 m2/g and 0.78 cm3/g. The poly(amic acid) contains the mesopores and macropores based on its pore size distribution curve. Regarding an acidic pH and abundance of functional groups, as-prepared tertiary poly(amic acid) was employed as a heterogeneous adsorbent of different types of heavy-metal ions, including Ag (I), Cr (III), and Cu (II). A removal efficiency > 90 % after 10 min for three heavy metal ions demonstrates a strong chelating capacity of as-prepared tertiary poly(amic acid). An adsorption capacity of > 50 mg per gram of poly(amice acid) was recorded for three heavy-metal ions with a pH of 3 or higher than 3. Poly(amic acid) exhibited good recyclability. This work exhibited the applicability of novel poly(amic acid) as an efficient adsorbent for the heavy metal ions removal from wastewater.

Application Prospect of Ion-Imprinted Polymers in Harmless Treatment of Heavy Metal Wastewater.

With the rapid development of industry, the discharge of heavy metal-containing wastewater poses a significant threat to aquatic and terrestrial environments as well as human health. This paper provides a brief introduction to the basic principles of ion-imprinted polymer preparation and focuses on the interaction between template ions and functional monomers. We summarized the current research status on typical heavy metal ions, such as Cu(II), Ni(II), Cd(II), Hg(II), Pb(II), and Cr(VI), as well as metalloid metal ions of the As and Sb classes. Furthermore, it discusses recent advances in multi-ion-imprinted polymers. Finally, the paper addresses the challenges faced by ion-imprinted technology and explores its prospects for application.

Performance of metakaolin-based geopolymer molecular sieve microspheres on dynamic recovery of Cu (II)

This study reports the in-situ transformation of geopolymers into molecular sieve using a method with mild conditions. The application of geopolymer zeolites for dynamic adsorption in continuous fixed beds has been less studied, and the application of adsorbents after adsorption has been less studied. Different metakaolin-based geopolymer molecular sieve microspheres (NaA-MSM, SOD-MSM) were prepared by in-situ conversion of metakaolin as raw material and NaOH as an alkali activator. The continuous fixed-bed adsorption performance was evaluated by varying the influent flow rate, initial metal concentration, and adsorbent dosage. The maximum adsorption capacities of NaA-MSM and SOD-MSM for Cu (II) were 698.14 and 523.84 mg·g−1, respectively. In the simulated solution of real lake water, the adsorption capacities of NaA-MSM and SOD-MSM for Cu (II) were 202.94 and 154.97 mg·g−1, respectively. The results show that the synthesized molecular sieve is an excellent adsorbent for Cu (II)-containing wastewater, and the application design of recycling heavy metals in wastewater by adsorption technology and degrading dyes has been successfully constructed.

Heavy metals in wastewater and fish collected from waste stabilization pond and human health risks in southwestern Ethiopia

IntroductionThis study aimed to measure the concentration of toxic heavy metals in wastewater samples and Nile tilapia (Oreochromis niloticus) species inhabiting wastewater (waste stabilization ponds) and evaluate their safety as a food source in southwestern Ethiopia. For this purpose, toxic metals like lead (Pb), cadmium (Cd), arsenic (As), and mercury (Hg) in wastewater samples and fish tissues (muscle, gill, and liver) were independently examined.MethodsA laboratory-based cross-sectional study was performed to ascertain the levels of Pb, Cd, As, and Hg in the fish tissues of O. niloticus and wastewater samples. Heavy metal levels were analyzed by microplasma atomic emission spectrometry (Agilent 4210 MP-AES) and hydrogen-generated atomic absorption spectrometry (HGAAS, novAA 400P, Germany).ResultsHeavy metal concentrations were measured in the following decreasing order (µg L−1): Cd > Pb > As > Hg in facultative and maturation ponds, with Cd (27.66 µg L−1) having the highest concentration and Hg (0.349 µg L−1) having the lowest concentration. Among the heavy metals detected in the wastewater samples, Hg showed a statistically significant difference between the sampling points (p = 0.023). The maximum metal concentration was measured for Pb (0.35 mg kg−1) and Cd (0.24 mg kg−1) in the muscle tissue of O. niloticus. The value of arsenic (0.02 mg kg−1) detected in fish edible muscles exceeded the FAO/WHO maximum permissible limit (MPL = 0.01) for human consumption. The carcinogenic and non-carcinogenic health risks of consuming fish due to trace metals were relatively low and posed fewer potential threats to human health. According to this finding, children were more susceptible to heavy metal exposure than adults.ConclusionDue to the high quantities of these harmful heavy metals, wastewater from oxidation ponds should not be used for fishing to avoid bioaccumulation. The target carcinogenic risk (TR) and target hazard quotient (THQ) indicated that all heavy metals were below the safe threshold. This research will provide a baseline for monitoring trace metals in various edible aquatic creatures and for future research in artificial habitats and regulatory considerations.

IMPACT OF DIFFERENT ORGANIC AND INORGANIC AMENDMENTS ON GROWTH AND YIELD OF MUNG BEAN IRRIGATED WITH TEXTILE EFFLUENTS

Water is an important substance for all life on earth, and it is essential for human beings, financial improvement, and the existence of ecological units. The quality and quantity of the water supply is very important, especially during irrigation. Due to the extensive measurement of water and colour associated with the manufacturing process, textile printing, and dyeing production lines around the world pose a major environmental risk. Textile wastewater contains a lot of pollutants including pH, temperature, shade, COD, BOD, TSS, TDS, EC, and heavy metals. This textile runoff continues to irrigate agricultural land, causing contamination of soils and plant systems with heavy metals. Therefore, adding organic and inorganic modifiers to soil is an effective technique for fixing heavy metals. Irrigate pots with textile wastewater of selected concentrations (10%, 25%, 50%, and 100%) collected in specific industrial sectors. The parameters of vegetative growth are reduced by increasing the concentration of textile effluent. Note the substantial reduction in the growth of plants applying wastewater at 100% concentration. In the case of T5, a significant increase in growth parameters was observed, where only tap water was used to pressurize the sludge, while dilute wastewater also enhanced growth at concentrations of 10% and 25%. For the chlorophyll content of mung bean plants, when the wastewater concentration is 100%, the recorded decrease is greater, followed by 10% and 25% respectively. The presence of heavy metals in wastewater reduces plant growth. In the experiment, all four treatments contained organic amendments (pressed sludge, poultry manure, biogas slurry, and farmyard manure). The other four treatment methods are pressure treatment of textile wastewater and the amount of organic modifier is 2%. By adding a correcting agent, the utilization rate of Cr is reduced, as the correcting agent will increase the pH of the soil, thus reducing the solubility of the metal. In addition, Cr can form insoluble complexes with organic materials, thus reducing its solubility.

Highly efficient photocatalyst fabricated from the recycling of heavy metal ions in wastewater for dye degradation

Water pollution and energy crisis are becoming global and strategic issues that people are closely concerned about. Green and energy-saving photocatalytic technology is developing rapidly in solving global energy crises and environmental pollution problems. Therefore, we propose the “kill two birds with one stone” strategy to design efficient photocatalysts for dye wastewater treatment by utilizing heavy metal ions in wastewater. The adsorption properties of Mordenite (MOR) were utilized to removal heavy metal ions (Cd2+ and Zn2+) from waste water, and the adsorbed heavy metal ions were dried and sulfurized to obtain CdS/ZnS/MOR(ZnCdM). Then, g-C3N4 was ultrasonically dispersed and composited with ZnCdM by self-assembly, 25 wt% ZnCdCM photocatalytic material was obtained with a degradation rate of 99.8% in 1.5 h for Rhodamine B(RhB). It was found that MOR can provid adequate support for active substances, and the surface of MOR with smaller sizes of CdS nanoparticles, ZnS nanoparticles and g-C3N4 nanosheets, which increased the specific surface area of the materials and improved the reactivity. The porous structure of MOR is favorable for the enrichment of RhB, and the electric field effect of MOR leads to the decrease of the photogenerated carrier complex rate in the semiconductor, which increases the catalytic efficiency. In addition, the double Z charge transfer mechanism formed by CdS, ZnS, g-C3N4 is favorable for separating photogenerated carriers. These synergistic effects improved the photocatalytic efficiency. This strategy will be a green and promising solution to water pollution and energy crisis.

Synthesis and fabrication of magnetically separable phosphate-modified magnetic chitosan composites for lead(II) selective removal from wastewater

To address the urgent need for efficient removal of lead-containing wastewater and reduce the risk of toxicity associated with heavy-metal wastewater contamination, materials with high removal rates and easy separation must be developed. Herein, a novel organic-inorganic hybrid material based on phosphorylated magnetic chitosan (MSCP) was synthesized and applied for the selective removal of lead (II) from wastewater. From the characterization and the experimental results can be obtained that the magnetic saturation strength of MSCP reaches 14.65 emu/g, which can be separated quickly and regenerated readily, and maintains high adsorption performance even after 5 cycles, indicating that the adsorbent possesses good magnetic separation performance and durability. Also, MSCP showed high selective adsorption performance for lead in the multiple metal ions coexistence solutions at pH 6.0 and room temperature, with an adsorption coefficient SPb-MSCP of 78.85%, which was much higher than that of MSC (the SPb-MSC was 11.59%). Additionally, in the single lead system, the sorption characteristics of Pb(II) on MSCP and MCP had obvious pH-responsiveness, and their adsorption capacity increased with the increase of solution pH, reaching the maximal values of 80.19 and 72.68 mg/g, respectively. It is noteworthy that the acid resistance of MSCP with an inert layer coated on the core is significantly improved, with almost no iron leaching from MSCP over the entire acidity range, while MCP has 7.63 mg/g of iron leaching at pH 1.0. Significantly, MSCP exhibited a maximum adsorption capacity of 102.04 mg/g, which matches the Langmuir model at pH 6.0 and 298.15 K, and points to the pseudo-second-order kinetics of the chemisorption process of Pb(II) on MSCP. These findings highlight the great potential of MSCP for Pb(II) removal from aqueous solution, making it a promising solution for Pb(II) contamination in wastewater.

Conversion of Phosphogypsum into Porous Calcium Silicate Hydrate for the Removal and Recycling of Pb(II) and Cd(II) from Wastewater.

The discharge of lead and cadmium wastewater, along with the pollution caused by phosphogypsum, represents a particularly urgent environmental issue. This study employed a straightforward hydrothermal method to convert phosphogypsum into porous calcium silicate hydrate (P-CSH), which was then used to remove and recover Pb(II) and Cd(II) from wastewater. The adsorption capacities of P-CSH for Pb(II) and Cd(II) were notably high at 989.3 mg/g and 290.3 mg/g, respectively. The adsorption processes adhered to the pseudo-second-order kinetics model and the Langmuir isotherm model. Due to identical adsorption sites on P-CSH for both Pb(II) and Cd(II), competitive interaction occurred when both ions were present simultaneously. Additionally, the adsorption efficacy was minimally impacted by the presence of common coexisting cations in wastewater. The dominant mechanisms for removing Pb(II) and Cd(II) via P-CSH were chemical precipitation and surface complexation. Moreover, the adsorbed heavy metals were efficiently separated and reclaimed from the wastewater through a stepwise desorption process. The primary components of the residue from stepwise desorption were quartz and amorphous SiO2. Following dissolution via pressurized alkaline leaching, this residue could be recycled for synthesizing P-CSH. This research offered a new strategy for the resourceful use of phosphogypsum and heavy metal wastewater.

A novel highly dispersed calcium silicate hydrate nanosheets for efficient high-concentration Cu2+ adsorption

Currently, the low cost and effective purification toward heavy metal ions in wastewater has garnered global attention. Herein, we used hydrothermal method to prepare highly dispersed calcium silicate hydrate in fluorite tailings. And the stacking thickness of calcium silicate hydrate layered morphology was less than 5 nm. For high concentration Cu2+ purification investigation in wastewater, we found that the equilibrium adsorption capacity reached 797.92 mg/g via the CSH with 3:2 Ca/Si molar ratio, be 1.43–21.8 times than that of reported data. Therein, the metal-metal exchange and deposition are the primary pathways for Cu2+ adsorption, and electrostatic attraction is the secondary pathway. And the relative ∼100 % removal rate of high-concentration Ni2+ and Cr3+ ions were confirmed via CSH prepared from different tailings. This method offers a cost-effective way to utilize tailings for preparing highly efficient adsorbents toward HMIs removal in wastewater.

Enhanced solar-driven steam generation and water purification using 3D arch solar evaporators

Steam generation strategy through solar-driven evaporators has now been widely recognized as one of the effective means to relieve the global fresh water crisis. Reducing heat loss has shown to be an effective way to improve the evaporation efficiency which has been overlooked in three-dimensional (3D) evaporators in the past. Herein, a superhydrophilic photothermal fabric was developed by the layer-by-layer assembly of carbon nanotubes followed by dip-coating with polyvinyl alcohol. The as-obtained photothermal fabric was designed as a 3D arch solar evaporator (ASE). The arch structure allowed the photothermal fabric to achieve double-sided water evaporation and a well-balanced saline water supply by controlling the height of the ASE. The ASE effectively captured the incident sunlight and demonstrated extraordinary thermal management performance, resulting in a saline water evaporation flux of 1.015–3.400 kg m−2 h−1 under 1 sun irradiation for 6 h. In addition, the proposed ASE exhibited excellent water purification for high salinity saline water, colored wastewater, and heavy metal wastewater. This work provides new insights into emerging solar steam generation systems by regulating the saline water supply balance.