Selective Removal Of Heavy Metals Research Articles

Bioinspired, Carbohydrate-Containing Polymers Efficiently and Reversibly Sequester Heavy Metals.

Water scarcity and heavy metal pollution are significant challenges in today's industrialized world. Conventional heavy metal remediation methods are often inefficient and energy-intensive, and produce chemical sludge. To address these issues, we developed a bioinspired, carbohydrate-containing polymer system for efficient and selective heavy metal removal. Using ring opening metathesis polymerization, we synthesized polymers bearing amphiphilic glucuronate side chains capable of selectively binding heavy metal cations in mixed media. In samples containing high concentrations of heavy metals (>550 ppb), these polymers rapidly form a filterable precipitate upon metal capture, reducing the concentration of cation to <1.5 ppb within 3 min, as measured by inductively coupled plasma mass spectrometry. This system effectively removes cadmium ions from highly contaminated solutions to levels below the Agency for Toxic Substances and Disease Registry limit for Cd2+ in drinking water and selectively removes both Cd2+ and Pb2+ from lake water spiked with trace amounts of metal. Acidification triggers protonation of the glucuronate groups, releasing the heavy metals and resolubilizing the polymer. This capture-and-release process can be repeated over multiple cycles without loss of binding capacity. As such, this study introduces a novel class of recyclable materials with pH-responsive properties, offering potential for applications in water remediation and beyond.

Removal of Lead and Zinc from Blast Furnace Sludge Through High Temperature Carbochlorination

A new dual kiln processing route has been proposed and investigated for removal of heavy metals from the zinc-rich fraction of blast furnace (BF) sludge and recovery of ferrous materials. The zinc in BF sludge exists both as ZnO and ZnS. The thermodynamic analysis indicates that the carbochlorination of the sludge shows a selective heavy metal removal. Lead can be removed at a temperature below 900°C followed by the zinc removal at higher temperatures, producing an iron-rich clean residue free of heavy metals in the end feasible for recycling back to ironmaking. High temperature carbochlorination experiments have been conducted with designed mini-pellets. The experimental results prove that via the proposed dual kiln route, a valuable zinc-rich fraction and a clean iron-bearing residue can be achieved with addition of iron chloride, leaving a small stream of lead-rich residue for further processing. This newly developed recycling flowsheet provides a sequential carbochlorination in two inter-connected rotary kilns, incorporated with efficient dust-capturing systems. In total, over 98% heavy metal removal has been achieved. The Zn-rich dust contains more than 60% of zinc, and the quality of the iron-rich residue is sufficient for re-use in the integrated steel works.

Efficient and Selective Removal of Heavy Metals and Dyes from Aqueous Solutions Using Guipi Residue-Based Hydrogel.

The presence of organic dyes and heavy metal ions in water sources poses a significant threat to human health and the ecosystem. In this study, hydrogel adsorbents for water pollution remediation were synthesized using Guipi residue (GP), a cellulose material from Chinese herbal medicine, and chitosan (CTS) through radical polymerization with acrylamide (AM) and acrylic acid (AA). The characteristics of the hydrogels were analyzed from a physicochemical perspective, and their ability to adsorb was tested using model pollutants such as Pb2+, Cd2+, Rhodamine B (RhB), and methyl orange (MO). The outcomes revealed that GP/CTS/AA-co-AM, which has improved mechanical attributes, effectively eliminated these pollutants. At a pH of 4.0, a contact duration of 120 min, and an initial concentration of 600 mg/L for Pb2+ and 500 mg/L for Cd2+, the highest adsorption capabilities were 314.6 mg/g for Pb2+ and 289.1 mg/g for Cd2+. Regarding the dyes, the GP/CTS/AA-co-AM hydrogel displayed adsorption capacities of 106.4 mg/g for RhB and 94.8 mg/g for MO, maintaining a stable adsorption capacity at different pHs. Compared with other competitive pollutants, GP/CTS/AA-co-AM demonstrated a higher absorption capability, mainly targeted toward Pb2+. The adsorption processes for the pollutants conformed to pseudo-second-order kinetics models and adhered to the Langmuir models. Even after undergoing five consecutive adsorption and desorption cycles, the adsorption capacities for heavy metals and dyes remained above 70% and 80%. In summary, this study effectively suggested the potential of the innovative GP/CTS/AA-co-AM hydrogel as a practical and feasible approach for eliminating heavy metals and dyes from water solutions.

Selective removal of heavy metals from wastewater using polyphenol nano-microspheres: Enhancing sequestration and regeneration performance through pH-responsive coordinated structural changes

The proficient advancement of nanoscale adsorbents assumes a pivotal role in the enhanced elimination of heavy metals to trace concentrations. Nevertheless, within the realm of engineering, the attainment of elevated selectivity and effective regeneration remains an arduous endeavor. In this context, we propose a novel structure-tunable sorption/regeneration mechanism by designing TA cross-linked polyphenolic nano-microspheres (PTA). These PTAs exhibit tunable pH-responsive metal coordination structures, enabling high sequestration and purification in removing heavy metals, and facilitating efficient regeneration. Taking Pb(II) as an example, under neutral conditions, the PTAs form a six-coordination configuration with Pb(II) ions, resulting in larger selectivity of Kd: 84400 mL/g with a 99 % removal efficiency even in the presence of various cations, anions, and organic acids. This performance far surpasses that of the commercial ion exchanger D001, exhibiting an enhancement factor of nearly 250 times, rendering it amenable for deployment in a wide array of contaminated water sources, encompassing lake water and industrial wastewater. Notably, the PTA also demonstrates exceptional practical utility, affording a voluminous treatment capacity of 5250 L per kilogram of adsorbent in wastewater scenarios. Furthermore, under acidic conditions, the transformation of PTA's metal coordination into a weaker two-coordination facilitates the efficient desorption of Pb(II) with an impressive efficiency of up to 99.0 % across multiple cycles. In contrast, commercial cheated resins D401 and D418 experience a significant 70 % decrease in reuse performances after the first cycle. This study provides a new perspective and platform for efficient adsorbent development through coordinated structural changes, it holds the potential to alleviate the challenges associated with deep restoration of heavy metal-contaminated wastewater.

Efficient and Superstable Mineralization of Toxic Cd2+ Ions through Defect Engineering in Layered Double Hydroxide Nanosheets

Water and soil pollution caused by toxic cadmium ions (Cd2+) is a serious threat to animals, plants, and human health. Discovering low-cost mineralizers which can efficiently and stably immobilize Cd2+ ions is therefore imperative for wastewater treatment and soil remediation. In this work, we report the successful development of a novel mineralizer for Cd2+ ion capture. A magnesium–aluminum layered double hydroxide (MgAl-LDH) with a monolayer structure (MgAl-mono) was first prepared and then calcined at 350 °C for 4 h to produce a defective MgAl-mono-350. MgAl-mono-350 offered a very high Cd2+ removal capacity (1385.5 mg/g at 25 °C) and the ability to reduce the concentration of Cd2+ in aqueous solution from 100 ppm to less than 50 ppb in 15 min (meeting the discharge standard of industrial wastewater). Detailed characterization and computational studies revealed that MgAl-mono-350 possessed abundant oxygen defects, thereby enabling superstable mineralization of Cd2+ via isomorphous substitution process,and the Cd2+ ions are immobilized in the generated CdAl-LDH structure. MgAl-mono-350 also offered outstanding selectivity for Cd2+ ions over other common ions. This work demonstrates the potential of defect-engineered LDH materials for the selective removal of heavy metals from polluted water.

Magnetic ion-imprinted polyacrylonitrile-chitosan electro-spun nanofibrous membrane as recyclable adsorbent with selective heavy metal removal and antibacterial fouling in water treatment

Water pollution has become one of the most concerned environmental issues on the worldwide scale. Due to the harmfulness of the heavy metal ions and microorganisms in wastewater, novel filtration membranes for water treatment are expected to simultaneously clear these pollutants. Herein, the electro-spun polyacrylonitrile (PAN) based magnetic ion-imprinted membrane (MIIM) were fabricated to achieve both selective removal of Pb(II) ions and excellent antibacterial efficiency. The competitive removal experiments showed that the MIIM displayed efficiently selective removal of Pb(II) (45.4 mg·g−1). Pseudo-second-order mode and Langmuir isotherm equation is well matched with the equilibrium adsorption. The MIIM showed sustained removal performance (~79.0 %) against Pb(II) ions after 7 adsorption-desorption cycles with negligible Fe ions loss of 7.3 %. Moreover, the MIIM exhibited excellent antibacterial properties that >90 % of E. coli and S. aureus were killed by the MIIM. In conclusion, the MIIM provides a novel technological platform for integration of multi-function with selective metal ions removal, excellent cycling reusability, and enhanced antibacterial fouling property, which can be potentially utilized as a promising adsorbent in actual treatment of polluted water.

Surface-modified ultrafiltration and nanofiltration membranes for the selective removal of heavy metals and inorganic groundwater contaminants: a review

The review critically highlights the state-of-art techniques for selective membrane fabrication, action mechanism, and performance for groundwater contaminant removal.

Selectivity toward heavier monovalent cations of carbon ultramicropores used for capacitive deionization

Electrolyte confinement inside carbon nanopores strongly affects ion electrosorption in capacitive deionization. A thorough understanding of the intricate pore size influence enables enhanced charge storage performance and desalination in addition to ion separation. In subnanometer pores, where the pore size is smaller than hydrated ion size, a dehydration energy barrier must be overcome before the ions can be electrosorbed into the pores. Ion sieving is observed when the dehydration energy is larger than the applied energy. However, when a high electrochemical potential is used, the ions can desolvate and enter the pores. Capitalizing on the difference in size and dehydration energy barriers, this work applies the subnanometer porous carbon material, and a high electrochemical ion selectivity for Cs+ and K+ over Na+, Li+, Mg2+, and Ca2+ is observed. This establishes a possible way for selective heavy metal removal by varying pore and solvated ion sizes. Our work also shows the transition from double-layer capacitance to diffusion-limited electrochemical features in narrow ultramicropores.

Selective removal of heavy metals by Zr-based MOFs in wastewater: New acid and amino functionalization strategy

Zr-based metal-organic frameworks (MOFs) have been developed in recent years to treat heavy metals, e.g. hexavalent chromium Cr6+ pollution, which damages the surrounding ecosystem and threaten human health. This kind of MOF is stable and convenient to prepare, but has the disadvantage of low adsorption capacity, limiting its wide application. To this end, a novel formic acid and amino modified MOFs were prepared, referred to as Form-UiO-66-NH2. Due to the modification of formic acid, its specific surface area, pore size, and crystal size were effectively expanded, and the adsorption capacity of Cr6+ was significantly enhanced. Under optimal conditions, Form-UiO-66-NH2 exhibited an excellent adsorption capacity (338.98 mg/g), ∼10 times higher than that reported for unmodified Zr-based MOFs and most other adsorbents. An in-depth study on the photoelectronic properties and pH confirmed that the adsorption mechanism of Form-UiO-66-NH2 to Cr6+ was electrostatic adsorption. After modification, the improvement of Cr6+ adsorption capacity by Form-UiO-66-NH2 was attributed to the expansion of its specific surface area and the increase in its surface charge. The present study revealed an important finding that Form-UiO-66-NH2 elucidated selective adsorption to Cr6+ in mixed wastewater containing toxic heavy metal ions and common nonmetallic water quality factors. This research provided a new acid and amino functionalization perspective for improving the adsorption capacity of Zr-based MOF adsorbents while simultaneously demonstrating their pertinence to target contaminant adsorption.

Selective removal of heavy metals from saline water by nanofiltration

Polyethylenimine (PEI) cross-linked P84 nanofiltration membranes were successfully developed through a facile stirring cross-linking method. The separation performance of the membrane was tailored by changing the concentration of the P84 casting solution. A systematic characterization, including chemical structure, surface morphology, surface charge, and separation performance, was carried out. Nanofiltration membranes with a high positive charge and hydrophilic surface were successfully fabricated. All the PEI cross-linked membranes showed high isoelectric points at pH from 8 to 8.9 and a mean pore radius from 0.389 to 0.474 nm. Under the influence of the Donnan effect and size exclusion, the 20%P84/PEI membrane showed an excellent water permeance of 27.7 ± 1.5 L m−2 h−1 bar−1 and a high rejection (>90%) for single-component heavy metal salts (ZnCl2, PbCl2, Ni(NO3)2 and Cu(NO3)2). A variety of mixed salt separation performance tests were performed. These results clearly indicate that the 20%P84/PEI and 22%P84/PEI membranes have a huge potential to remove and concentrate copper ions from aqueous solutions. In particular, the 24%P84/PEI membrane is promising in the selective removal of various heavy metals from highly saline water.

Mo3S132− Intercalated Layered Double Hydroxide: Highly Selective Removal of Heavy Metals and Simultaneous Reduction of Ag+ Ions to Metallic Ag0 Ribbons

AbstractWe demonstrate a new material by intercalating Mo3S132− into Mg/Al layered double hydroxide (abbr. Mo3S13‐LDH), exhibiting excellent capture capability for toxic Hg2+ and noble metal silver (Ag). The as‐prepared Mo3S13‐LDH displays ultra‐high selectivity of Ag+, Hg2+ and Cu2+ in the presence of various competitive ions, with the order of Ag+&gt;Hg2+&gt;Cu2+&gt;Pb2+≥Co2+, Ni2+, Zn2+, Cd2+. For Ag+ and Hg2+, extremely fast adsorption rates (≈90 % within 10 min, &gt;99 % in 1 h) are observed. Much high selectivity is present for Ag+ and Cu2+, especially for trace amounts of Ag+ (≈1 ppm), achieving a large separation factor (SFAg/Cu) of ≈8000 at the large Cu/Ag ratio of 520. The overwhelming adsorption capacities for Ag+ (qmAg=1073 mg g−1) and Hg2+ (qmHg=594 mg g−1) place the Mo3S13‐LDH at the top of performing sorbent materials. Most importantly, Mo3S13‐LDH captures Ag+ via two paths: a) formation of Ag2S due to Ag‐S complexation and precipitation, and b) reduction of Ag+ to metallic silver (Ag0). The Mo3S13‐LDH is a promising material to extract low‐grade silver from copper‐rich minerals and trap highly toxic Hg2+ from polluted water.

Synergistic DFT-guided design and microfluidic synthesis of high-performance ion-imprinted biosorbents for selective heavy metal removal

International water security has become unprecedentedly complicated, therefore, effective and selective removal of hazardous materials, especially toxic heavy metal ions, are significant for effluent purification. In this regard, ion-imprinted polymers with special recognition cavities have received much attention. However, configuration screening and performance optimization of functional materials by trial-and-error design method is undoubtedly time- and money-consuming. In this study, high-performance ion-imprinted chitosan microspheres (ICSMs) were successfully designed via density functional theory (DFT) calculation and synthesized via facile microfluidic technology. As-synthesized ICSMs exhibited highly uniform morphology ( D av = 420.6 µm, CV = 3.6%) and ultra-high adsorption capacity ( q max = 107.12 mg g −1 ). The adsorption isotherm was best fitted to the Langmuir model while the kinetic data followed the pseudo-second order model, indicating a dominant role of chemisorptions. Also, ICSMs displayed satisfactory stability and reusability (95.34 mg g −1 , after 5 cycles). Moreover, the selective adsorption mechanism was quantitative revealed by electronegativity, electrophilicity index, adsorption energy ( E a ) and bond length. This study is expected to lay a foundation for high-performance biosorbents design and synthesis for future water remediation. • High-performance ICSMs were obtained by DFT-guided design and microfluidic synthesis. • Ultra-high adsorption property for targeted metal ions (107.12 mg g −1 ) was proved. • Target ions selective removal from mono- and multi-component systems was achieved. • Selectivity mechanism was quantitative revealed by adsorption energy and bond length. • Superior and stable re-adsorption efficiency (> 95 mg g −1 after 5 cycles) was verified.

Overview

It is an indisputable observation, beyond climate change: that the urgent development of simple new technologies, to ensure the supply of quality fresh water for cities and towns, industry and agriculture, presents an existential challenge for humanity.&#x0D; Several novel technologies that fill that need show that the job is not impossible. They are summarized in this volume. They are environmentally friendly and inexpensive.&#x0D; They include techniques for seawater desalination, wastewater sterilization –including viruses-, selective removal of heavy metals from industrial wastewater, efficient concentration of wastewater slimes to recycle water, and the prevention of water cavitation for much cheaper transport. Other new techniques like high temperature reactions achieved in low temperature water, and low energy desalination are in the wings. Borrowing from biology , new and edible class of surfactants is environmentally friendly, and can replace standard surfactants in present useage. The new technologies are cheap and scalable.

Effective and selective removal of heavy metals from industrial effluents using sustainable Si–CD conjugate based column chromatography

The present investigation deals with the green synthesis of aqueous-stable and highly fluorescent carbon dots (CD) by hydrothermal treatment of tender leaf extract of Ficus benghalensis. The synthesized CD was characterized. Carbon dots were of an average size of 2.28 nm with a blue-green fluorescence emission at 317 nm and showed high selectivity and specificity for iron and nickel amongst the different tested heavy metals with a LOD of 0.0015 μmol/mL and 0.000014 μmol/mL respectively. Further, we functionalized silica with the prepared carbon dot to generate an adsorbent for purification of contaminated water. A short bed adsorbed column system was designed for determining the efficiency of adsorption. As envisioned approximately, 77% and 74% removal of Fe and Ni was observed when the metal salts were eluted individually. Purification efficacy was analysed using an industrial electroplating effluent, which showed adsorption of 74% and 79% for Fe and Ni respectively.

One-dimensional graphene for efficient aqueous heavy metal adsorption: Rapid removal of arsenic and mercury ions by graphene oxide nanoribbons (GONRs)

There is a knowledge gap for the application of one-dimensional graphene in the adsorption process. Our hypothesis was based on the fact that graphene oxide nanoribbons (GONRs) as one-dimensional graphene with more desired edges and specific surface area than other carbonaceous nanomaterials have more oxygen containing functional groups (active sites) on their edges and basal planes and therefore are more capable in adsorption of pollutants. In this regard, we synthesized GONRs by unzipping of multi-walled carbon nanotubes (MWCNTs) and investigated the adsorption behavior of GONRs by ultrasonic-assisted adsorptive removal of As(V) and Hg(II) ions from aqueous solution. The obtained results showed that As(V) ions are more favorably adsorbed onto the GONRs than Hg(II) ions and with increasing initial As(V) and Hg(II) ions concentration to 300 ppm, the equilibrium adsorption uptake of the synthesized GONRs increases to 155.61 and 33.02 mg/g for As(V) and Hg(II) ions, respectively through a rapid separation process in just 12 min. Also, three kinetic models and Freundlich and Langmuir adsorption isotherms were applied to evaluate the obtained experimental results. Our findings highlight the potential application of GONRs as one-dimensional graphene adsorbent with more desired edges than MWCNTs and graphene oxide (GO) and high adsorption capacity for selective removal of heavy metals.

2D water-stable zinc-benzimidazole framework nanosheets for ultrafast and selective removal of heavy metals

Owning to the unique structure and dimensionality, two-dimensional (2D) layered nanosheets have received increasing research interests. In this study, for the first time, we evaluate the ability of water stable 2D zinc based metal-organic framework (MOF) nanosheets, Zn(Bim)(OAc), to capture heavy metals in the aquatic system. The obtained novel adsorbent exhibits an ultrathin structure with an average thickness of 7.05 nm. Owning to their ultrathin thickness and highly exposed active sites, the as-prepared ultrathin Zn(Bim)(OAc) nanosheets exhibit the maximum adsorption capacity of 253.8 mg/g for Pb(II) and 335.57 mg/g for Cu(II), respectively, which is far superior adsorptive uptake in contrast to their corresponding bulk-type MOF. Meanwhile, the saturation process was rapid, within 30 min for Cu(II) and 90 min for Pb(II). Intriguingly, Zn(Bim)(OAc) nanosheets own a remarkable selectivity for Pb(II) and Cu(II) over other heavy metal ions in the mixed system, which is attributed to the strong affinity of imino and hydroxyl groups for Pb(II) and Cu(II) within Zn(Bim)(OAc) nanosheets. This work highlights new prospects in designing ultrathin 2D nanoadsorbents for the use in environmental remediation.

THE ADSORPTION OF HEAVY METALS FROM INDUSTRIAL WASTEWATER USING SARGASSUM CRASSIFOLIUM

Sargassum crassifolium is the origin strains of macroalgae from Indonesia which was the most effectively adsorb heavy metals from liquid solution and it was investigated the adsorptive capability of heavy metals in industrial wastewater. The macroalgae were collected at Kotok Besar Island, Seribu Island, North Jakarta, Indonesia and were treated with the variety of pH 2, 3, 4, 5 and 9 for 60 minutes oscillation, in duplicate assessment. The macroalgae were selectively effective for removal of Cd, Hg, and Pb compared with other heavy metals, achieving 75-99.05% adsorption efficiency, mostly in acidic condition for 60 minutes oscillation, except Hg. The selectivity order for other metal ion uptake by S. crassifolium was Cu>Fe>Co>Ni>Cr with percentage removal below 56%. Due to the low cost, availability and significantly high adsorption capability, the brown macroalgae S. crassifolium is able to be used for selective removal of heavy metals from industrial wastewater effectively in acidic pH range

Selective removal of heavy metal ions in aqueous solutions by sulfide-selector intercalated layered double hydroxide adsorbent

Remaining largely under-appreciated, a majority of metal ion sorbents are limited in their target selectivity. In this work, a 3D sulfide intercalated NiFe-layered double hydroxide (NFL-S) hierarchical sorbent has been synthesized for selective heavy metal removal. The intercalation of sulfurated groups in the interlayer of the layered double hydroxide (LDH) nanosheets endows NFL-S as a selective heavy metal ion filter; the selectivity of NFL-S for heavy metals is in the order of Pb2+ > Cu2+ ≥ Zn2+ > Cd2+> Mn2+, and NFL-S has high kd values for Pb2+ (∼106 mL/g) and Cu2+ (∼105 mL/g). Scanning electron microscopy, X-ray photoelectron spectroscopy and powder X-ray diffraction were used to analyze the composition of the as-prepared nanoadsorbent. The selective adsorption behavior was systematically studied using batch experiments, and the performance was evaluated through kinetic and isotherm studies. Moreover, the adsorption mechanism of heavy metals by NFL-S through surface complexation was also investigated, which shows great potential for water decontamination.

Designing an Optimal Ion Adsorber at the Nanoscale: The Unusual Nucleation of AgNP/Co2+–Ni2+ Binary Mixtures

Selective removal of heavy metals from water is a complex topic. We present a theoretical–computational approach, supported by experimental evidences, to design a functionalized nanomaterial that i...

Purification of wastewater from the ions of copper, zinc, and lead using an electrolysis method

Heavy metals penetrate water reservoirs as a result of natural and anthropogenic processes, thereby accumulating in soil, bottom sediment, sludge, and can further migrate into groundwater and surface water. The main sources of heavy metals penetration into natural waters are the insufficiently treated waste waters from many branches of industry. That renders relevance to the problem of removing heavy metals from wastewater in order to prevent excessive pollution of water reservoirs. Among existing methods of water purification from heavy metals’ ions at significant volumes of industrial wastewater, the electrochemical methods are rather promising. The advantage of this method is a possibility to recycle the used regeneration solutions with obtaining metals that are suitable for reuse. This paper reports results of research into the processes of electrochemical removal of heavy metals’ cations from diluted aqueous solutions in one­and two­chamber electrolyzers. When conducting the study in a two­chamber electrolyzer, the anode and cathode regions were separated by the anion­exchanging membrane MA­40. A dependence of the influence of hardness, solutions’ pH, anodic current density, and the duration of electrolysis on efficiency of the removal of heavy metals’ ions was investigated. It is shown that the ions of zinc, copper and lead are effectively removed from aqueous solutions using the electrolysis at a starting concentration of 10 mg/dm3. It was established that at the low concentrations of ions, the output for current, when reducing metals, reached (4–20)·10­4 % and changed little with concentration. It was determined that the efficiency of water purification from heavy metals’ ions using electrolysis increases with an increase in pH of the medium and with a decrease in the hardness of water. In the two­chamber electrolyzers, these factors exert almost no effect on purification efficiency. The paper shows the prospect of using electrolysis for the selective removal of heavy metals from tap, softened and natural water. A given purification method makes it possible to not only post­clean wastewater to the maximally permissible concentrations, but also enables the purification of water from natural water bodies to the quality of drinking water