Treatment Of Metal Pollution Research Articles

Spatial–temporal variation and source analysis of heavy metals in different land use types in Beilun District (2015 and 2022)

The soil environment plays an important role in urban ecosystems. To study the heavy metal contamination of soil in Beilun District, Ningbo, we collected soil samples from 60 points in urban and peri-urban areas of Beilun District and analyzed the spatiotemporal variation and sources of heavy metal pollution in various land-use types. The results shown that the heavy metal contents in 2015 and 2022 were higher than the background soil values of Ningbo city, and there was an accumulation of heavy metals over these 7 years. The contents of heavy metals in green belts and woodland in 2022 were higher than those in 2015, while there was no significant change in agricultural land. The heavy metal contents in both years were mainly in the order green belts > agricultural land > woodland. The spatiotemporal distribution of heavy metal content showed that heavy metal pollution in Beilun District was concentrated in five industrial areas, and there was a trend toward the disappearance of highly polluted points. But the single-factor pollution index, pollution load index (PLI), and geoaccumulation index (Igeo) indicated that there was no significant heavy metal pollution in Beilun District, and individual elements at specific points showed slight pollution. The source analysis results showed that the main source of Hg is chemical, As is mainly derived from agricultural, Cr, Ni and Cu are mainly derived from natural, the main sources of Zn and Cd are electroplating and machinery activities, and the main source of Pb is traffic. These results specify a reference for future investigation on urban soil heavy metals, and the source apportionment results provide a scientific foundation for subsequent soil heavy metal pollution treatment.

Application and mechanism of carbonate material in the treatment of heavy metal pollution: a review.

Among the many heavy metal pollution treatment agents, carbonate materials show strong flexibility and versatility by virtue of their high adsorption capacity for heavy metals and the characteristics of multiple and simple modification methods. It shows good potential for development. This review summarizes the application of carbonate materials in the treatment of heavy metal pollution according to the research of other scholars. It mainly relates to the application of surface-modified, activated, and nano-sized carbonate materials in the treatment of heavy metal pollution in water. Natural carbonate minerals and composite carbonate minerals solidify and stabilize heavy metals in soil. Solidification of heavy metals in hazardous waste solids is by MICP. There are four aspects of calcium carbonate oligomers curing heavy metals in fly ash from waste incineration. The mechanism of treating heavy metals by carbonate in different media was discussed. However, in the complex environment where multiple types of pollutants coexist, questions on how to maintain the efficient processing capacity of carbonate materials and how to use MICP to integrate heavy metal fixation and seepage prevention in solid waste base under complex and changeable natural environment deserve our further consideration. In addition, the use of carbonate materials for the purification of trace radioactive wastewater and the safe treatment of trace radioactive solid waste are also worthy of further exploration.

A Review on Development of Porous Aluminosilicate-Based Zeolite Adsorbent for Heavy Metal Pollution Treatment

Heavy metal contamination endangers human health and has been identified as a global issue. The rising concentration of heavy metals in industrial and domestic wastewater has prompted the quest for effective technologies and treatments to remove them. Zeolite is a promising material for eliminating heavy metals from diverse sources that pollute wastewater. Zeolite is a crystal comprised of hydrated aluminosilicates of alkali and alkaline earth metals in a threedimensional crystal network composed of easily controllable SiO4 4− and AlO4 5− . This review focuses on the critical analysis of the application of several zeolites for the adsorption of heavy metals from wastewater, namely Cd(II), As(III and V), Cr(III and VI), Cu(II), Pb(II), Ni(II), Mn(II), and Hg(II). The results of heavy metal removal reported by zeolites are summarized, and the chemical modification of zeolites with acid/base/salt reagents, surfactants, and metal reagents has been investigated, compared, and discussed. The adsorption/desorption capabilities, systems, operational parameters, isotherms, and kinetics of zeolites are then explained and compared.

Insights into the Mechanism of Selective Removal of Heavy Metal Ions by the Pulsed/Direct Current Electrochemical Method.

Heavy metal pollution treatment in industrial wastewater is crucial for protecting biological and environmental safety. However, the highly efficient and selective removal of heavy metal ions from multiple cations in wastewater is a significant challenge. This work proposed a pulse electrochemical method with a low-/high-voltage periodic appearance to selectively recover heavy metal ions from complex wastewater. It exhibited a higher recovery efficiency for heavy metal ions (100% for Pb2+ and Cd2+, >98% for Mn2+) than other alkali and alkaline earth metal ions (Na+, Ca2+, and Mg2+ were kept below 3.6, 1.3, and 2.6%, respectively) in the multicomponent solution. The energy consumption was only 34-77% of that of the direct current electrodeposition method. The results of characterization and experiment unveil the mechanism that the low-/high-voltage periodic appearance can significantly suppress the water-splitting reaction and break the mass-transfer limitation between heavy metal ions and electrodes. In addition, the plant study demonstrates the feasibility of treated wastewater for agricultural use, further proving the high sustainability of the method. Therefore, it provides new insights into the selective recovery of heavy metals from industrial wastewater.

Monolithic melamine foam@COF composite: Preparation, characterization and applications in ultrafast removal and on-site quick assessment of Cd2+ pollution

The assessment and treatment of heavy metal pollution are eternal subjects of environmental protection. Facile on-site assessment of heavy metal pollution and efficient, rapid removal of pollutes are still challenging. Covalent organic frameworks (COFs) hold great promise as absorbents for heavy metal pollution treatment. To overcome the application limits of COF powders, a COF-based monolithic composite is prepared by direct in-situ growth of an N/O-rich COF on the surface of a melamine foam (MF). The resultant MF@COF inherits the macro-porous channels of MF, the good crystallinity of COF, and integrates the attractive features of monolithic materials such as ease of operation, facile and highly efficient recovery, and good reusability. The abundant N/O groups endow MF@COF with powerful capture capability towards various heavy metal ions. Its maximum adsorption capacity for Cd2+ is 278.45 mg/g, and the adsorption equilibrium can be reached within 1–3 s. The adsorption kinetic of Cd2+ by MF@COF follows the pseudo-second-order kinetic model, and the adsorption isotherm conforms to Freundlich model. Rapid adsorption, together with the easy-to-operate feature of monolithic material, make the ultrafast water purification possible. Meanwhile, MF@COF works well for the highly efficient enrichment of Cd2+ to realize the naked-eye detection of Cd2+ pollution at low levels, thus may be developed as an important tool for both on-site assessment and rapid treatment of heavy metal pollution.

First Report of Stemphylium lycopersici Causing Leaf spot on Sedum plumbizincicola in Hunan Province of China.

Sedum plumbizincicola is a perennial succulent herb that can hyperaccumulate high concentrations of cadmium and zinc (Liu et al. 2017). In October 2021, a leaf spot disease occurred on S. plumbizincicola seedlings in a nursery in Changsha (28°13' N; 112°56'E), the Hunan Province of China. Almost 30% of the nearly 1 million seedlings were infected. Symptoms initially appeared as small brown spots on the leaf surface or edges, gradually enlarged, becoming oval, and bearing chlorotic lesions with dark brown borders. Eventually, the center of the lesions became sunken and then fell off. Eight symptomatic plant samples were collected by five-point sampling method (Zheng et al. 2018). Small pieces of 5×5 mm were excised from the lesion margins, sterilized with 70% ethanol for 10 s, 0.1% HgCl2 for 40 s, rinsed with sterile distilled water three times, and then cultured on potato dextrose agar (PDA) at 26 °C for 5 days in the dark. Fungal colonies showing similar morphology were observed from all the isolated samples and, in total, eight fungal strains were obtained. On PDA, fungal colonies were initially white, and later become light gray. After cultured on V8 juice agar (V8A, each litre of medium contains 200 mL of V8 juice, 3 g of CaCO3 and 15 g of agarose) for 14 days (Hyowon et al. 2016), conidia of a representative isolate SY-1 were produced, which were oblong, muriform, with blunt ends and conical apex, pale to light brown, and constricted at the 1 to 3 major transverse septa, 38.34-46.68 μm×11.67-18.34 μm (n=50). These morphological characteristics were consistent with that of Stemphylium lycopersici (Nasehi et al. 2016). The internal transcribed spacer (ITS) region of rDNA and the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene of representative isolates SY-1 to SY-3 were amplified and sequenced using the primer pairs ITS4/ITS5 and gpd1/gpd2 as described previously (Woudenberg et al. 2017). BLASTn analysis showed that ITS sequences of isolates SY-1, SY-2 and SY-3 (accession nos. OP317641, OQ852042 and OQ852043) had more than 99% identity with Stemphylium sp, while GAPDH sequences (OP331223, OQ858620 and OQ858621) had 100% identity with S. lycopersici KR911813 (Sun et al. 2016). A concatenated ITS-GAPDH phylogenetic tree grouped our isolates within the S. lycopersici clade. For the pathogenicity test, one-month-old potted S. plumbizincicola seedlings were inoculated with conidia suspension (105 conidia/ml), which was induced on V8A. Four sites of each leaf of the potted S. plumbizincicola plants were dropped with a conidia suspension of strain SY-1, with 10 μL per site. Leaves treated with sterile water were served as controls. All of the inoculated seedlings were placed in a growth chamber at 26°C with a photoperiod of 12 h. The pathogenicity tests were repeated twice, with each had three replicative plants. After 7 days, all the inoculated leaves developed brown spots resembling those observed in the nursery, whereas the control plants remained symptomless. Stemphylium lycopersici was specifically re-isolated and identified by morphological and molecular methods (accession nos. OQ852045 for ITS and OQ858622 for GAPDH, respectively), thus fulfilling Koch's postulates. To our knowledge, this is the first report of S. lycopersici causing leaf spot on S. plumbizincicola in China. Since S. plumbizincicola played an important role and widely planted for heavy metal pollution treatment (Jiang et al. 2010), and this disease might seriously influence the S. plumbizincicola seedling breeding, identification of the pathogen might provide a foundation for the diagnosis and control of the disease.

Progress of Mine Land Reclamation and Ecological Restoration Research Based on Bibliometric Analysis

The mining of mineral resources has caused serious damage to land and significant pressure on ecological environment. During the repairing of damaged land and degraded ecosystems, there have been many pieces of literature related to land reclamation and ecological restoration (LRER) that have emerged. To understand the progress and prospect of LRER research, it is necessary to sort out such pieces of literature, analyze the current research status, and forecast the future research directions. Here, Bibliometrix R-package was used to analyze 2357 articles, which were derived from the core database of Web of Science, to explore the development of LRER from 1990 to 2022. The results are as follows. (1) The annual scientific output results show that both the number of articles published on LRER and the number of articles annually citied were increasing gradually from 1990 to 2022. (2) High-frequency keyword analysis indicates that heavy metal (Cd, Pb) pollution remediation is a research hotspot. The cluster analysis (CA) and multiple correspondence analysis (MCA) show that there are two clusters in the current research of LRER, in which one surrounds heavy metal pollution and the other focuses on ecological restoration of mining areas. The two clusters correspond to the remediation and ecological restoration (rehabilitation) stages of stepwise ecological restoration, respectively. Thematic evolution analysis shows that, for more than 30 years, mine drainage and heavy metal pollution treatment, soil reconstruction (soil profile reconstruction, soil improvement), and vegetation restoration have been the focus of research. (3) Future research should focus on the relationship between mine ecological restoration and carbon sequestration and the relationship between ecological restoration and biodiversity in mine areas. In addition, LRER technology exchange, international cooperation, and industrialization are also main directions of development. Generally, in this study, metrology software (Bibliometrix R-package 3.1.4) from the literature was used to sort out the relevant literature on LRER over the past 30 years so as to provide reference for future research on LRER.

Synthesizing sulfhydryl-functionalized biochar for effectively removing mercury ions from contaminated water.

Biochar is regarded as an effective adsorbent for heavy metal pollution treatment, and functional optimization is still needed to improve its performance. We created raw biochar (BC and BP) from corn straw and pine sawdust, which were modified to produce sulfhydryl-modified biochar (MBC and MBP). Isothermal adsorption experiments and adsorption kinetics experiments as well as the related model fitting were performed to evaluate the adsorption performance of biochar on Hg(II). According to the results of the Langmuir model fitting, the maximum adsorption capacities of sulfhydryl-modified biochar were 193.05mg/g (MBC) and 178.04mg/g (MBP), respectively, which were approximately 1.6 times higher than the raw biochar. The results showed that adding sulfhydryl groups to biochar can improve its adsorption performance. The prompt effect resulted from the sulfhydryl modification providing additional functional groups and enhanced chemisorption and physical adsorption properties.

A new strategy for treating Pb2+ and Zn2+ pollution with industrial waste derivatives Humin

Metal pollution caused by industrial waste accumulation is a long-term and far-reaching problem. Humin (HM), as a highly condensed organic component insoluble in alkaline or water solution, is often discarded as humic acid industrial waste. However, the abundant active functional groups in HM reported by some researches make it possible for HM to remove metals. In this study, a waste reuse strategy was proposed to reduce the pressure of industrial metal pollution on the environment. HM was obtained from lignite waste residue. Scanning electron microscopy, energy spectrum and Fourier infrared spectroscopy, combined with the adsorption models were employed to reveal the mechanism of HM adsorption. The results showed that HM had multiple adsorption mechanism and high biological stability. The adsorption capacity of HM to Zn2+ and Pb2+ were 194.88 mg/g and 289.59 mg/g respectively. HM adsorbed Zn2+ mainly by physical multilayer adsorption. And the adsorption of Pb2+ by HM was mainly a monolayer chemical reaction, which depended on its active functional groups and the exchange of valence electrons. Notably, HM could simultaneously remove Pb2+ and Zn2+ and almost did not affect its original adsorption capacity to single ions. These results will provide a new strategy for the treatment of metal pollution in the future and alleviate the pressure of multiple metal pollution of the environment.

Advances in Bioremediation of Agricultural Soil Contamination

With the rapid advancement of industrialization and agricultural intensification, the issue of farmland pollution has garnered significant attention. This paper introduces the sources and hazards of farmland pollution, along with the types, principles, and technical advantages of bioremediation. Additionally, it makes a brief prediction of future farmland restoration efforts. Research indicates that the primary sources of farmland pollution currently include four factors: the natural environment, atmospheric deposition, irrigation water, and agricultural production activities. There are two primary methods of remediation for farmland contamination: phytoremediation and microbial remediation. Phytoremediation is mainly used in heavy metal pollution treatment and can be divided into hyper-accumulation plants and low-accumulation crops based on the remediation method. Microbial remediation, meanwhile, is primarily utilized to remediate organic pollution and assist phytoremediation.

Study on treatment effect assessment of heavy metal pollution in Taihu Lake Sediments Based on the rapid development of Yangtze River Delta Urban Agglomeration in China

<p>In order to explore an effective assessment method for the treatment effect of heavy metal pollution in the sediment of Taihu Lake in China, based on the research background analysis and literature review, this paper reconstructs the spatial niche suitability model and applies it to the effect assessment of heavy metal pollution treatment in Taihu Lake sediment. The study found that the pollution degree of heavy metals in Taihu Lake sediment is as follows: North water area, West water area, South water area and East water area. The assessment results of the effect of heavy metal pollution treatment in Taihu Lake sediment by using SNSM are as follows: As > Cd > Hg > Ni > Mn > Zn > Pb > Cr > Cu. The four heavy metals that pose the greatest threat to the effect of Taihu Lake sediment are As, Cd, Hg and Ni; in particular, As and Cd are carcinogenic heavy metals, which the management authorities should pay special attention to. The research results of this paper are of great significance in supporting the government to formulate relevant policies for treating Taihu Lake and helping the management departments improve the treatment effect of heavy metal pollution in Taihu Lake sediments.</p>

Sponge-supported monolithic materials of porphyrin covalent organic frameworks for selective recognition, convenient removal and extraction of Cd2+

Adsorption is a cheap, energy-efficient, and easy-to-operate method for heavy metal pollution treatment. As highly porous and crystalline polymers, covalent organic frameworks (COFs) hold great promise as the adsorbents of metal ions. Herein, two hydroxyl-functionalized porphyrin COFs (2,3-DhaTph and 2,5-DhaTph) were synthesized, characterized and demonstrated to be good adsorbents of cadmium(II) ion (Cd2+). Via the chemical coordination of abundant phenolic hydroxyls to Cd2+ and the fluorescent response of porphyrin moieties to Cd2+, 2,3-DhaTph realized bifunction of specific optical recognition and highly efficient adsorption of Cd2+. To further simplify the removal operation of Cd2+, bulk monolithic materials (PS@COFs) were prepared via the in-situ growth of 2,3-DhaTph or 2,5-DhaTph on the pore wall of a dopamine-treated heat-resistant polyurethane sponge. Compared to the COFs, PS@COFs showed faster adsorption kinetics and shorter adsorption equilibrium time due to the interconnected large porous channels and the uniform distribution of thin COF layer on the pore wall. The characteristics of easy operation and good reusability (≥ 6 times) endow PS@COFs with great potential in practical applications, more than 99% Cd2+ could be easily removed from water samples by them. PS@COFs were also demonstrated to work well for the extraction of various heavy metal ions from polluted food samples (rice and wheat), achieving the detection of these metal ions.

First Report of Damping-off on Sedum plumbizincicola Caused by Rhizoctonia solani AG 2-1 in China.

Sedum plumbizincicola X.H. Guo et S.B. Zhou sp. nov. is a plant species of the family Crassulaceae that has the ability to hyperaccumulate cadmium and zinc in high concentrations (Liu et al. 2017). In April of 2018 and 2019, a disease of damping-off was observed on S. plumbizincicola seedlings in a nursery in Changsha (28°13'N; 112°56'E), the Hunan Province of China, in which nearly 1 million seedlings were planted. Approximately 40% of the surveyed plants were infected. The affected plants displayed water-soaking on the shoots and stems, and chlorosis on the leaves. As the disease spread upward, leaf stalks or the whole plants became wilted and collapsed. Five diseased stem and leaf samples were collected. Symptomatic tissues were excised and surface sterilized with 70% ethanol for 10 s, and 0.1% HgCl2 for 2 min, washed with sterile distilled water for three times, and then cultured on potato dextrose agar (PDA) at 26°C in darkness. Fungal colonies were similar in morphology: white, light gray to brown, with hyphae branched at nearly right angles, septa near the branching point and constrictions at the base of hyphal branches. After 10 days, white-gray to brown sclerotia were produced. The morphological characteristics were consistent with those of Rhizoctonia solani J.G. Kühn (Sneh et al. 1991). Genomic DNA of a representative isolate was extracted using the cetyltrimethylammonium bromide method. The internal transcribed spacer (ITS) region of rDNA was amplified and sequenced with the primer pairs ITS4/ITS5 (White et al. 1990). When analyzed by the BLASTn program, the ITS sequence (GenBank Accession No. MN961664) had 100% identity to the corresponding gene sequence of R. solani anastomosis group (AG) 2-1(Accession Nos: LC202869.1 and MH862641.1). In addition, primers Rhsp1/ITS4B and Rhsp2/ITS1F specific for R. solani, and AG21sp/ITS4B specific for R. solani AG 2-1 were also used (Salazar et al. 2000). Results revealed that our isolate was R. solani AG 2-1. Pathogenicity was confirmed via in vivo inoculation of one-month-old S. plumbizincicola seedlings in sterilized nursery soil with four representative isolates. For each pot, five 5-mm-diameter mycelial plugs from 7-days old colonies on PDA were placed in the soil near the base of the stems. Plants inoculated with agar plugs without mycelium served as controls. The inoculated plants were kept in a growth chamber at 25°C with a 12/12 h light/dark cycle. Pathogenicity tests were performed twice, with three replicative potted plants for each isolate in each test. Approximately 25 days after inoculation, the damping-off symptoms resembling those observed in the field were displayed on the inoculated plants, while no obvious symptoms were observed on the control plants. R. solani was re-isolated from all infected plants and molecularly characterized, thus confirming Koch's postulates. R. solani has been previously reported as the pathogen of damping-off disease in many plants, such as canola (Paulitz et al. 2006) and oat (Zhang et al. 2016). However, to the best of our knowledge, this is the first report of R. solani causing damping-off of S. plumbizincicola in China. S. plumbizincicola is widely planted for heavy metal pollution treatment in China. The occurrence of this disease could seriously affect the production of the seedlings, and management strategies should be developed.

Remediation of lead polluted soil by active silicate material prepared from coal fly ash

To improve the effect of coal fly ash on the remediation of heavy metal polluted soils, the active silicate material (ASM) was prepared by coal fly ash and the remediation of lead polluted soils by ASM was investigated in this study. To study the reaction mechanism between ASM and Pb(II) in soil, the Pb(II) adsorption by ASM was investigated by a series of batch experiments. The result shows that the maximum adsorption capacity of ASM was 300.62 mg g−1 according to the Langmuir isotherm model. The average adsorption energy obtained from the D-K model revealed that the adsorption process of ASM is the ion-exchange process. To apply the ASM to the remediation of lead polluted soils, the soil stabilization experiment and pot experiment were carried out. The results reveal that ASM can reduce the mobility and bioavailability of lead in the soils by transforming the lead from exchangeable fraction, carbonate fraction and reducible fraction to oxidizable fraction and residual fraction. Moreover, ASM can improve the growth of pakchoi by promoting the production of chlorophyll. Furthermore, ASM can reduce the Pb accumulation of pakchoi by inhibiting the absorption of lead in the roots. It is anticipated that this study can provide a novel active silicate material for the application of coal fly ash in heavy metal pollution treatment.

Multi-Evolutionary Game Research on Heavy Metal Pollution Control in Soil: Based on a Third-Party Perspective

The introduction of third-party governance models for the treatment of soil heavy metal pollution has promoted the marketization, professionalization, and efficiency of pollution treatment, but also can result in distortions of relevant stakeholder relationships and conflicts of interest. The game relationship among the government, soil-polluting companies, and third-party governance companies may solve the practical dilemma of comprehensive management of soil heavy metal pollution and establish a good cooperative mechanism. We constructed a three-party evolutionary game model to analyze the interaction mechanism of each agent’s strategy choice as well as the evolution of each agent’s strategy choice under different parameter trends and simulation analyses. The research showed that the amount of fines and supervision costs, rent-seeking costs and governance costs, and government subsidies and rent-seeking benefits were key factors affecting the evolution and stability strategies of government departments, soil-polluting companies, and third-party governance companies. By cooperating with third-party governance companies, the government can effectively suppress the improper behavior of soil-polluting companies. The conclusions of the study are helpful to broaden the research boundary of soil heavy metal pollution treatment and provide theoretical guidance for the treatment of soil heavy metal pollution in China.

Evaluation method for heavy metal pollution control effect in rural areas of northern Anhui Province

AbstractSoil is an important part of human survival, and people's lives cannot be separated from soil. At present, soil pollution in China is becoming more and more serious, especially heavy metal pollution. Based on this, a method for evaluating the effect of heavy metal pollution treatment in rural areas in northern Anhui was proposed. Taking Liulangguan Lane, Nanling, and Dapu in the south of Anhui Province as the study area, the PLSR model was used to collect soil heavy metal content in the area as sample data. The fuzzy comprehensive evaluation method was used to analyze the effect of heavy metal pollution control in rural areas. The results show that most of the soil quality evaluation grades are grades 2 and 3 and need to be retreated. And the evaluation accuracy of the method is always greater than 0.9500, and the evaluation results are more credible.

Effective removal of heavy metals from an aqueous solution with poly(N-vinylimidazole-acrylamide) hydrogels

ABSTRACT In this study poly(N-vinylimidazole-acrylamide) p(N-VI-AAm) hydrogels were prepared as an adsorbent for adsorptive removal of lead (II) and copper (II) ions from aqueous solution. Adsorption studies showed that poly(N-vinylimidazole-acrylamide) p(N-VI-AAm) hydrogels can be effectively used to remove heavy metals. Hydrogel characterization was done by FTIR and SEM. The effect of the removal conditions such as contact time, pH, temperature, and initial metal ion concentration on the Pb (II) and Cu (II) ions binding was also tested. Maximum adsorption was achieved at 30°C and 35°C for Pb (II) and Cu (II) after 24 h, respectively. Experimental capacities were calculated as 262 and 53 mg g−1 for lead and copper, respectively. The isotherms were analyzed with Langmuir and Freundlich models. Briefly, this economic and high adsorption performance poly(N-VI-AAm) hydrogel is a promising candidate for sewage disposal and metal pollution treatment.

Few-layered metal-organic framework nanosheets as a highly selective and efficient scavenger for heavy metal pollution treatment

Current techniques trialed for the sequestration of heavy metals (HMs) are typically metal ion specific. The deployment of adsorbents as amenable choices for the simultaneous elimination of several HMs remained a big challenge. Herein, few-layered CoCNSP nanosheets with periodically aligned sulfur species were exfoliated from layered metal-organic frameworks (MOFs) through a facile-operating method. Laboratory scale experiments revealed that CoCNSP nanosheets showed selective uptake in the order of Co(II), Zn(II), Cd(II), Ni(II) ≪ Cu(II) < Pb(II) < U(VI) < Hg(II) in both single-component and multi-component systems. Attractively, CoCNSP nanosheets showed high distribution coefficients (Kd ~ 106–107 mL/g), fast capture dynamics (<40 min), and ultrahigh uptake capacities (716, 661, 534, and 325 mg/g for Hg(II), U(VI), Pb(II), and Cu(II), respectively). Further, CoCNSP nanosheets could tolerate the influence of ionic strength (up to 100 mM), maintained high adsorption efficiency over a wide pH range, and showed good recycle performance for three times. X-ray photoelectron spectroscopy and theoretical density functional theory calculations demonstrated that the superior adsorption ability dominantly originated from the inner-sphere coordination between sulfur species and HMs. Finally, the traits of simple synthetic method, low-cost and non-toxic raw ingredients, as well as remarkable capture performance, make CoCNSP nanosheets superior to other scavengers. These findings reflect the important synthetic achievement in the deployment of MOFs for alleviating the environmental problems caused by HMs.

Dual-responsive copolymer hydrogel as broad-spectrum adsorbents for metal ions

A copolymeric hydrogel (PEGMA) with poly(ethylene glycol) methyl ether acrylate (PEGA), 2-methoxyethyl acrylate (MEA) and acrylic acid (AA) was synthesized in this study. The obtained PEGMA hydrogel exhibited sensitive response to pH and temperature and showed excellent adsorption properties for many metal ions, such as Fe(Ⅲ), Pb(Ⅱ), Zn(II), Ni(II), Mn(II) and Co(II), etc. Fe(Ⅲ) and Pb(Ⅱ) were selected to study thermodynamics and kinetics. The adsorption process followed pseudo-second-order kinetics equation. The adsorption isotherms could be described by Freundlich isotherm models. The maximum adsorption amount was calculated to be 195.43 (Fe3+) and 176.06 (Pb2+) mg/g. Besides, using the thermal and pH responsiveness, the PEGMA hydrogels can quickly release the adsorbed molecules with control. The heavy metal ions loaded PEGMA hydrogels could also be easily regenerated by diluted hydrochloric acid and still keep a major adsorption capacity. After five cycles, the adsorption ability remained more than 90% of the original PEGMA. Thus, the PEGMA hydrogels may be new high-performance and environment friendly material for metal pollution treatment with promising developmental potential.

Shape memory aerogels from nanocellulose and polyethyleneimine as a novel adsorbent for removal of Cu(II) and Pb(II)

This study describes the preparation of an aerogel adsorbent based on nanofibrillated cellulose(NFC) and polyethyleneimine(PEI) via electrostatic combination without chemical crosslinking. Purely physical crosslinking between NFC and PEI was confirmed by attenuated total refraction-Fourier transform infrared spectroscopy (ATR-FTIR) and thermogravimetric analysis (TGA). The NFC/PEI hybrid aerogels exhibited good structural stability and shape recovery in water. Absorption experiment shows that the hybrid aerogels are excellent adsorbents for the removal of heavy metal ions owing to the highly porous structure and the existence of plenty of amine groups. Thermodynamic and kinetic study showed pseudo-second-order equation and Langmuir model (R2 > 0.999) as the best fit. The maximum adsorption capacity of Cu(II) and Pb(II) according to Langmuir model was 175.44 mg/g and 357.44 mg/g, respectively. Besides, the Cu(II) or Pb(II) loaded NFC/PEI aerogel could be easily regenerated by EDTA and retain the adsorption capacity after repeatedly using. This environmentally friendly hybrid aerogels with high-performance are promising candidates for sewage disposal and metal pollution treatment.