Heavy Metal Adsorption Capacity Research Articles

Biomass inherent metal interfere carbothermal reduction modification of biochar for Cd immobilization

Metal salt laden are frequently used to enhance the heavy metal adsorption capacity of biochar. The present study indicates that CaS loading biochar can be modified from the carbothermal reduction reaction between CaSO3 (modification agent) and carbon matrix. The CaS transformation ratio as indicated by XPS spectra was significantly improved by the CaSO3 loading content. The coprecipitation reaction induced by the CaS in biochar can significantly enhance the adsorption capacity of heavy metals (Cd). And, the Cd adsorption capacity can be enhanced up to >100 mg/g and increases with increasing CaS ratio in the biochar. In addition, the adsorption process was rapid and could be balanced within several minutes (~ 5 min). Furthermore, the interaction reaction between the modification agent and the inherent metal in the biomass was examined in the biochar pyrolysis preparation process. Interestingly, MgCl2 inherent metal salt can combine with the original CaSO3 to produce a new mineral, resulting in a decrease in CaS. However, KCl, a more thermally stable biomass-derived metal salt, exhibited a weak combination ability with the modification agent. Accordingly, this type of secondary reaction reduces the Cd adsorption capacity owing to the decrease in the number of adsorption sites (CaS).

Study on Adsorption of Heavy Metals Cu and Zn by Microplastics Under Different Aged Factors

Microplastics are widely distributed in a variety of environments, absorbing heavy metals in the environment while aging due to various environmental factors. In this paper, the effects of different aging factors (pH, DOM, and H2O2) on the adsorption capacity of heavy metals Cu and Zn on polyethylene microplastics (PE-MPs) were investigated, and the changes in physical and chemical properties of PE microplastics were analyzed. The results demonstrate that H2O2 aging bears the greatest effect on the adsorption effect of PE microplastics, dissolved organic matter (DOM) aging has the least effect on the adsorption effect of PE microplastics, and the adsorption effect of microplastics aged with pH=9 is stronger than that aged with pH=4; the adsorption kinetics model of microplastics fitted to the pseudo-second-order kinetic model, and the thermodynamic model fitted to Langmuir model; aging mainly changed the surface structure of microplastics, increased the Zeta potential of microplastics, introduced more oxygen-containing functional groups, and finally affected the ability of microplastics to adsorb heavy metals. The research provides data reference for understanding the influence of different aging on the adsorption capacity of heavy metals in microplastics.

Adsorption of Heavy Metals on Bentonitic Soil for Use in Landfill Liners

Hazardous heavy metal ions such as copper, zinc, nickel, chromium, cadmium, and lead engender a potential risk to human health. Among the processes involved in the retention of these contaminants, adsorption is advantageous for removing toxic metals because of its environmentally friendly aspect, efficiency, and low-cost operation. Information on the adsorption of heavy metals in soils from the semiarid region of northeastern Brazil is still scarce. In this study, the adsorption of heavy metals (Cd, Cu, Zn, Ni, and Pb) by a semiarid Brazilian bentonitic soil is investigated. This soil has been used as a bottom liner in an experimental municipal solid waste (MSW) cell located in Campina Grande, State of Paraíba, Brazil. The experimental cell consists of a landfill unit on an experimental scale, with the same constructive elements of a sanitary landfill. Disturbed and undisturbed samples of the investigated soil were collected at a quarry in the rural zone of Boa Vista (state of Paraiba, Northeast Brazil). Sorption attributes were determined via batch tests with a soil-solution ratio of 1 : 12.5 (4 g of dry soil to 50 mL of solution). Linear, Freundlich, and Langmuir isotherms were fitted to the experimental data, using as fitting parameters Pearson correlation coefficient ([Formula: see text]) and [Formula: see text] value with a significance level [Formula: see text]. The ascending order of maximum adsorption capacity for heavy metals followed the series Ni < Cr < Zn < Cd < Cu < Pb. The maximum adsorbent capacities obtained were similar to those of other Brazilian soils and other adsorbents. Therefore, the studied soil has a high potential to be used in the retention of heavy metals.

Gradient heating induced better balance among water transportation, salt resistance and heat supply in a high performance multi-functional solar-thermal desalination device.

Solar-driven desalination (SDD) is a promising technology for addressing water scarcity. However, how to overcome the trade-off between water transportation and heat supply of the evaporator to achieve a high evaporation rate and good salt tolerance simultaneously remains a challenge. Here, a novel all-in-one multi-functional SDD evaporator undergoing gradient heating is used. This evaporator incorporates a hydrophilic PDA (polydopamine)@CNT(carbon nanotube)/PVA (polyvinyl alcohol) aerogel with vertically aligned structures as the water evaporation layer, enabling rapid water transportation. Surrounding the evaporation layer, there is a photothermal hydrophobic CCP (cotton/CNT/polydimethylsiloxane) film that serves as the heating layer, enhancing the heat supply to the evaporation layer. This innovative design strikes a favorable balance between water transportation and heat supply, facilitating high evaporation rates and good salt tolerance simultaneously, while also maximizing electricity generation. Due to the wettability difference between the evaporation layer (PVA aerogel) and heating layer (CCP film), a record stable temperature gradient of nearly 70 °C was formed between the CCP film and the PVA aerogel under 1 sun irradiation, so that heat on the high-temperature CCP film was continuously transferred to the low-temperature aerogel through its thermal conductive network, leading to a high evaporation rate of 6.96 kg m-2 h-1 under 1 sun irradiation in 5.0 wt% sodium chloride (NaCl) brine (higher than the world average seawater salinity (3.5 wt%)). Meanwhile, high flux directional flow of brine generated 130 mV stable voltage and 120 μA circuit current. Furthermore, the evaporator illustrates good stability for consecutive 7 days of testing and shows industry-leading comprehensive performance of SDD in actual use. More importantly, it was tested in real Bohai seawater under weak natural light, and fresh water generated can meet the recommended daily intake of water for 2.6 households and the simultaneously generated voltage reaches above 60 mV. In addition, the evaporator exhibits good adsorption capacity for heavy metals and dye molecules. This simple and universal solar evaporation structure is suitable for the assembly of gradient thermal structures for most solar thermal materials reported in the literature, which provides a new route for maximizing the use of solar energy for freshwater and electricity generation.

Efficient removal of heavy metals by endophytic bacteria Staphylococcus succinus H3.

Heavy metal pollution is a serious and difficult environmental problem. With increasing heavy metal content in industrial wastewater, an environmentally friendly and efficient treatment method must be identified. Considering the ability of endophytic bacteria to adsorb metal ions, this paper explored the heavy metal resistance, adsorption, and adsorption mechanisms and performance of S. succinus H3, an endophytic bacterium. S. succinus H3 exhibited metal resistance at 4 mM Cu2+ and 5 mM Mg2+. The adsorption rate of Cu2+ and Mg2+ ions by the live/dead strain was approximately 70%, and the adsorption capacity was positively correlated with the metal ion concentration. The kinetics and isothermal models were used to study the process of S. succinus H3 adsorption on Cu2+. It exhibits a good correlation with the Freundlich isothermal model. The N-H group, protein C=O group, polysaccharide C-O group, O-H group and some lipids are the main functional groups in the cell wall. S. succinus H3 may bond with the amine group to adsorb Mg2+ through complexation/coordination and may form a copper complex after adsorbing Cu2+. S. succinus H3 has a live adsorption rate of 15% in eight mixed metal ion systems at a 50 mg/L concentration. The study results can lay a foundation for expanding the bacterial resource pool of pollutant treatment and improving the efficiency for sewage treatment. The high heavy metal adsorption capacity of microorganisms has a decisive role in industrial wastewater treatment by microorganisms. Such microorganisms with high metal resistance and adsorption capacity to heavy metals can thrive in industrial wastewater, remove heavy metals efficiently, and greatly improve the efficiency of wastewater treatment. The study results can lay a theoretical foundation for the use of S. succinus H3 to biologically treat heavy metal wastewater in the future.

Recycling of Organic Waste: An Overview of Pálinka Distillery Mash Composting

Organic waste generation has been extending to an alarming level in most areas of the world, and its sustainable management is required. In Hungary, the amount of organic waste is increasing significantly, especially in pálinka manufacturing - a Hungarian hard liquor - producing a great quantity of mash residue, mostly grape pomace spent wash, a non-hazardous food waste that is a suspension left over by the distillation of fermented spirits. Around two hundred thousand tons of fruit waste are generated annually, and its full recycling and legal disposal are unprecedented in Hungarian distilling plants, threatening the environment if disposed of incorrectly. In this paper, we focused on reviewing the Pálinka mash composting, where the biggest challenge for its treatment is its initial pH, around 4, which can be successfully neutralized with mineral additives. The applied additives were chosen by their beneficial physical, chemical, and biological qualities. Accordingly, andesite and alginite were employed in the experimental composting. The results of our observation have confirmed that the mineral additives can establish valuable compost or fertilizer, favourably altering the dynamics of the decomposition and synthesis reactions. As an experiment on mash composting technology, we also tested the mature mash compost in culture vessel experiments for heavy metal adsorption capacity of the ma tube mash compost using lettuce (Lactuca sativa) and tomato (Solanum Lycopersicum) as test plants. The plants were irrigated with lead (Pb), and iron (Fe) contaminated water, and then it was determined the metals accumulation capacity of the plants and growing media with an Atomic Absorption Spectrometer (AAS). The study could compare the rate of heavy metal accumulation by different plant parts and ratios of Pálinka mash compost in the growing media.

Effect of Drying–Rewetting cycles on the metal adsorption and tolerance of natural biofilms

Drying–rewetting (D-RW) cycles can induce changes in biofilms by forcing the microbial community to tolerate and adapt to environmental pressure. Existing studies have mostly focused on the impact of D-RW cycles on the microbial community structure, and little attention has been paid to how D-RW cycles may change the biofilm tolerance and adsorption of heavy metals. We experimentally evaluated the effect of repeated D-RW cycles on the Cd2+ and Pb2+ adsorption and tolerance of biofilms. The equilibrium adsorption capacity of the biofilm decreased as the number of D-RW cycles was increased, which was attributed to a change in affinity between the biofilm and metal ions. For a binary metal system, the D-RW cycles affected the competitive adsorption of Cd2+ and Pb2+ by the biofilm. A synergistic effect was observed with one and three D-RW cycles, while an antagonistic effect was observed for the control film and five D-RW cycles. The tolerance of the biofilm to Cd2+ and Pb2+ increased with the number of D-RW cycles. The stress from the D-RW cycles may have increased the relative abundance of drought-tolerant bacteria, which altered the biofilm functions and thus indirectly affected the heavy metal adsorption capacity.

Nanocomposite hydrogel engineered hierarchical membranes for efficient oil/water separation and heavy metal removal

The contaminants of oily sewage and heavy metal ions have been increasingly released into the aquatic environment, which causes a severe threat to both ecosystem and human health. However, it is still difficult to use a single separation technology to effectively deal with such a complex hazardous system to ensure the water safety and environmental remediation. Herein, a novel nanocomposite hydrogel-coated membrane was designed by one-step dip-coating of tannic acid (TA)/sodium alginate (SA)/3-aminopropyltriethoxysilane (APTES) co-depositing strategy, which combines the robust adhesion of TA, the hierarchical architecture induced by APTES and the strong hydration ability of SA. The as-prepared membrane exhibits excellent hydrophilicity and underwater superoleophobicity, which achieves efficient separation for various oil/water emulsions and outstanding anti-oil fouling performance. Meanwhile, the excellent heavy metal adsorption capacity was realized due to the abundant adsorption sites (-COO-, –NH2 and phenolic hydroxyl) and large surface area caused by hierarchical structures. Most interestingly, the fabricated membrane also presented strong chemical stability over a wide pH range 3–11, high salt tolerance and good resistance to anhydrous ethanol corrosion. The designed superwetting membranes show great potential for the purification of oil/water emulsion and the removal of heavy metal ions to effectively remediate the aquatic environment by the concept of ‘killing two birds by one stone’.

Typhoon triggers estuarine heavy metal risk by regulating the multifractal grainsize of resuspended sediment

The turbulent boundary layer generated by wind in the estuarine surface water serves as a main factor affecting the distribution of suspended particulate matter (SPM) and suspended sediment concentration (SSC). In this study, representative typhoon-induced variation of surface fine SPM (<63 μm) was simulated in the Yangtze River Estuary (YRE) under two time scenarios. Each scenario contained four grainsize SPM fractions named Fraction 1 (<8 μm), Fraction 2 (8–16 μm), Fraction 3 (16–32 μm), Fraction 4 (32–63 μm). The typhoon-induced resuspended multifractal SSC quantification (TRMSQ) based on the relationship between SPM grainsize and heavy metal adsorption capacity was proposed to assess the variation in the resuspended threat of heavy metal to 6 key estuarine protected objects (three reservoirs & three national reserves) between Scenarios 1 and 2. The results presented that Fraction 3 exhibited the maximum increment in SSC resuspension mass and longest regression time from typhoon. Combined with TRMSQ, chromium (Cr) was calculated to be the riskiest typhoon-induced factor. The integrated resuspended risk of heavy metals for each protected object tends to increase from the northwest of Chongming Island (1.2) towards the maximum turbidity zone (>9) downstream, with an estuary-wide mean of 3.3.

Removal Efficiency of Heavy Metals Such as Lead and Cadmium by Different Substrates in Constructed Wetlands

In order to find an efficient and economical wetland substrate to treat mine wastewater containing various heavy metals, and effectively realize the resource utilization of water treatment residuals, in this paper, the treatment efficiency of mine wastewater containing various heavy metals was investigated using unburned ceramsite prepared from water treatment residuals (UCWTR) and clay ceramsite. The continuous dynamic test results showed that the removal rate of Pb, Cd, Cu, Zn, and Fe can reach more than 98.5% after the UCWTR-based CWs runs for 56 days, and its concentration was 30.05%, 24.85%, 20.82%, 14.63%, and 7.91% lower than that of the clay ceramsite-based CWs, respectively. SEM, XPS, and FT-IR showed that the characteristic peaks of two ceramsites were basically similar. The ceramsite undergoes ion exchange, coordination complexation, and chelation reaction with Pb, Cd, Cu, Zn, and Fe under the action of the gel of internal groups -OH, C=O, Al-OH, Si-Fe-O and C-S-H. Compared with clay ceramsite, the ion exchange reaction and chelation reaction of -OH effect and the coordination reaction of C=O effect of carboxyl group in UCWTR were enhanced. In conclusion, using UCWTR as a CWs substrate can effectively enhance the adsorption capacity of heavy metals, providing a scientific basis for the application of UCWTR-based CWs in mine wastewater treatment.

Zirconium oxide with graphene oxide anchoring for improved heavy metal ions adsorption: Isotherm and kinetic study

Heavy metal contamination is a major environmental issue worldwide and a significant public health risk. However, developing environmentally sustainable and technically viable solutions or adsorbents for treating water contamination caused by heavy metals is urgently needed. In this work, an eco-friendly approach of obtaining a new composite material called ZrO2/GO that was prepared from the synthesized nano zirconium oxide (ZrO2) and graphene oxide (GO) prepared from spent carbon rods in zinc carbon batteries. ZrO2/GO was analyzed by XRD, SEM, BET, EDX, and FTIR to learn more about its composition and structure. The batch approach determined the optimal sorption conditions, including pH4, 50 mg ZrO2/GO, 150 mg/L U(VI), and 50 min of sorption time. ZrO2/GO was found to have a 128 mg/g sorption capacity. The Langmuir and 2nd-order kinetic equations can be exploited to elucidate the adsorption approach with reasonable accuracy. Since sorption is exothermic when it occurs naturally, thermodynamic restrictions were also envisioned. ZrO2/GO retains over 92% heavy metal ions (VI) removal efficiency even after 7 cycles. ZrO2/GO shows assurance as a potent sorbent material to extract hexavalent heavy metal ions and adsorption capacity from massive solution volumes.

Effect of graphene and graphene oxide on antibiotic resistance genes during copper-contained swine manure anaerobic digestion.

Copper is an important selectors for antibiotic resistance genes (ARGs) transfer because of metal-antibiotic cross-resistance and/or coresistance. Due to carbon-based materials' good adsorption capacity for heavy metals, graphene and graphene oxide have great potential to reduce ARGs abundance in the environment with copper pollution. To figure out the mechanics, this study investigated the effects of graphene and graphene oxide on the succession of ARGs, mobile genetic elements (MGEs), heavy metal resistance genes (HMRGs), and bacterial communities during copper-contained swine manure anaerobic digestion. Results showed that graphene and graphene oxide could reduce ARGs abundance in varying degrees with the anaerobic reactors that contained a higher concentration of copper. Nevertheless, graphene decreased the abundance of ARGs more effectively than graphene oxide. Phylum-level bacteria such as Firmicutes, Bacteroidetes, Spirochaetes, and Verrucomicrobiaat were significantly positively correlated with most ARGs. Network and redundancy analyses demonstrated that alterations in the bacterial community are one of the main factors leading to the changes in ARGs. Firmicutes, Bacteroidetes, and Spirochaetes were enriched lower in graphene reactor than graphene oxide in anaerobic digestion products, which may be the main reason that graphene is superior to graphene oxide in reduced ARGs abundance. Additionally, ARGs were close to HMRGs than MGEs in the treatments with graphene, the opposite in graphene oxide reactors. Therefore, we speculate that the reduction of HMRGs in graphene may contribute to the result that graphene is superior to graphene oxide in reduced ARGs abundance in anaerobic digestion.

Ecological risk assessment based on soil adsorption capacity for heavy metals in Taihu basin, China

Due to the toxicity, bioaccumulation, non-biodegradability and perseverance of heavy metals, their risk assessment is essential for soil quality management. The Hakanson potential ecological risk index (RI), which considers the effects of heavy metal concentration and toxicity, has been widely used in soil ecological risk assessment. However, RI overlooks the influence of soil properties on the mobility and availability of heavy metals in risk assessment. To fill this gap, this study sought to develop an improved ecological risk index (IRI), which incorporates soil adsorption into RI, and applied it to evaluate the ecological risk of heavy metals in the soil of the Taihu basin, China. The soil adsorption models based on the Gradient Boosting Decision Tree (GBDT) was used to predict the soil adsorption capacity of five heavy metals (i.e. cadmium, chromium, copper, lead, zinc). The soil adsorption capacity in 1446 sites in the Taihu basin was predicted by the GBDT models and was assigned as the weight of IRI. The risk assessment results of the five metals in the Taihu basin showed that 40% of the sites were at a moderate risk level and 60% of the sites were at a slight risk level based on the RI. The value of IRI in the basin ranged from 11.1 to 75.5, with a mean value of 28.1. IRI differed from RI in spatial distribution due to the influence of soil adsorption. The comparative analysis between the metal contents in sediments and surrounding soils confirmed the tremendous influence of soil adsorption on ecological risks, indicating that soil adsorption should be taken into consideration in soil risk assessment.

Experimental and theoretical studies on the adsorption characteristics of Si/Al-based adsorbents for lead and cadmium in incineration flue gas

Si/Al-based adsorbents are effective adsorbents for capturing heavy metals in incineration flue gases at high temperatures in the furnace. In this work, the adsorption characteristics and adsorption mechanisms of Si/Al-based adsorbents for lead and cadmium vapors were studied using a combination of experimental and density functional theory (DFT) calculations. The trapping performance of a series of Si/Al-based adsorbents for Pb and Cd vapors was investigated using a self-designed gas-solid two-phase rapid adsorption experimental system. The results showed that kaolinite and montmorillonite exhibited better heavy metal adsorption capacity than SiO2 and Al2O3, and were significantly stronger for Pb than for Cd. Chemisorption dominated the capture of Pb/Cd by Si/Al-based adsorbents at high temperatures. The results of DFT calculations indicated that the chemisorption mechanisms dominated the adsorption of Pb and Cd species on the metakaolinite (001) surface, and the adsorption energy of Pb species on the metakaolinite surface was greater than that of Cd species. The exposed O atoms and unsaturated Al atoms of metakaolinite (001) surface were effective adsorption active sites for heavy metals and their chlorides. In the adsorption reaction, the binding of Pb/Cd atoms and surface exposed O sites, as well as the strong interaction between Cl and unsaturated Al atoms, were responsible for the capture of Pb and Cd chlorides by metakaolinite.

Preparation and characterization of sodium polyacrylate grafted montmorillonite nanocomposite for the adsorption of cadmium ions form aqueous solution

High-efficiency adsorbents made from clay minerals have a wide application in remediation of soil and water pollution, especially in the treatment of refractory and highly toxic heavy metals. Montmorillonite itself has a good adsorption capacity and a large modification space for its layered structure. Therefore, carboxylate polymer grafted montmorillonite was developed to improve the adsorption capacity of heavy metals in this paper. Two kinds of modified preparation routes were compared, and a series of batch adsorption tests were conducted to evaluate the influence degree of parameters (contact time, pH, temperature, and cadmium concentration). The structural changes of montmorillonite samples before and after modification were characterized by a series of microscopic analyses and measurement techniques. The results show that the silicon hydroxyl produced by the hydrolysis of silane coupling agent can indeed be grafted by dehydration condensation with Si/Al-OH on clay surface. The grafting chain can be greatly increased by C=C double bond breaking polymerization. The polycarboxylate group can effectively improve the adsorption performance of modified montmorillonite for cadmium ions. The maximum adsorption capacity of modified montmorillonite increased by about 224.75%, reaching 63.49 mg/g. The adsorption model of montmorillonite conforms to Langmuir monolayer adsorption model, while modified montmorillonite samples exhibit Freundlich adsorption model and S-type isothermal adsorption curve characteristics of resin. The preparation method of neutralizing after polymerization of acrylic acid was proposed to be better, which provides technical guidance for scientific and efficient application.

Effects of Biofilms on Trace Metal Adsorption on Plastics in Freshwater Systems.

The formation of plastisphere on plastics and their potential impact on freshwater ecosystems have drawn increasing attention. However, there is still limited information about the effects of plastisphere on the heavy metal adsorption capacity and the related mechanism of plastic debris in different freshwaters. Herein, the trace metal adsorption capacity, kinetics and adsorption mechanisms of virgin and biofilm-covered plastic debris were investigated. Polypropylene (PP) and polyethylene terephthalate (PET) plastic debris were placed in three freshwaters (Xuanwu Lake, Donghu Lake and the Qinhuai River) for 45 days to incubate biofilms. Batch adsorption experiments were performed to compare the adsorption processes of trace metal on virgin and biofilm-covered plastics. Results showed that biofilms increase the adsorption of metals on plastics, and the adsorption isotherms were well fitted by the Langmuir model. Furthermore, the adsorption capacities for lead (Pb(II)) were higher than that of cadmium (Cd(II)) and zinc (Zn(II)), with 256.21 and 277.38 μg/g (Pb(II)) adsorbed in biofilm-covered PP and PET, respectively, in Xuanwu Lake. The adsorption kinetics of metals on plastic debris were significantly affected by the biofilms, by switching the intraparticle diffusion for virgin plastic debris to film diffusion for the biofilm-covered plastic debris. Moreover, the complexation of functional groups within the biofilms might mainly contribute to the increases of metal adsorption, involving the participation of oxygen and nitrogen groups. Overall, these results suggested that biofilms reinforce the potential role of plastics as a carrier of trace metals in freshwaters.

Adsorption performance of layered double hydroxides for heavy metals removal in soil with the presence of microplastics

Microplastics (MPs) are widely presence in soil, and the uncertain influence of MPs is ineluctable. In this study, the influence of removal efficiency for heavy metals by LDHs with the presence of polyethylene (PE) and polypropylene (PP) is investigated. And the removal efficiency of heavy metals Cu2+, Pb2+, Zn2+, Ni2+ by LDHs from soil is investigated by contact time, initial concentration, PP/PE contents, pH and coexisting ions. The adsorption capacities of heavy metals with the presence of PP/PE are larger and the effects with high content of PP/PE is more obvious on removal of heavy metals. The isothermal experiment data are well described by the Generalized Langmuir isothermal model, denoting that the adsorption sites on the absorbents are certain, and the sites are inhomogeneous with different adsorption energy. In order to further explore the influence of PP/PE on the removal of heavy metals by LDHs, the interaction between LDHs and PP/PE is analyzed by XRD, FT-IR, Zeta potential and SEM. The sites energy distribution theory is employed to analyze the distribution of accessible adsorption sites and the heterogeneity of sites. The results show that with the presence of PP/PE in soil, LDHs interacts with PP/PE preferentially on account of electrostatic attraction, and the combination of LDHs and PP/PE increases the accessible adsorption sites for the removal of heavy metals and is beneficial to the adsorption process. These findings contribute to understanding environmental behavior of heavy metals with the presence of MPs and guide the application of LDHs in soil.

Investigating the zeolite and bentonite adsorbent effect on different parameters of soil

Contamination of soils and groundwater resources has become one of the most serious global environmental problems in recent years. The use of natural and inexpensive adsorbents such as zeolite is one of the appropriate methods to prevent the spread of contaminants and increase the adsorption capacity of the soil. In this research, the behaviour of the mixture of sand with 15% kaolinite clay is investigated at first, in both conditions of non-contaminated and contaminated with lead nitrate. Due to the limited adsorption capacity of the sand containing kaolinite, different percentages of zeolite adsorbent were added to this mixture to investigate the adsorption capacity and changes in strength parameters of the soil and adsorbent mixture. According to the results of the atomic adsorption test, zeolite has a favorable effect on increasing the adsorption capacity of heavy metals in soils such that by adding 5% zeolite, the amount of lead adsorption capacity increases by about 70%. The dynamic behaviour of these compounds in both conditions of non-contaminated and contaminated with lead nitrate was studied. Dynamic behaviour shows that in the combination of soil with both types of adsorbents, by increasing the concentration of heavy metal, the cycles corresponding to Ru decreases.

Binder‐Free Wood Converted Carbon for Enhanced Water Desalination Performance

AbstractThe design and synthesis of high‐performance and economical carbon electrodes play a critical role in developing energy‐efficient water desalination technologies. As a sustainable approach, low‐cost and abundant biomass materials are promising candidates to prepare porous carbon for capacitive deionization. In this study, binder‐free porous carbon sheets are successfully prepared using natural balsa, pine, and basswood by thermal carbonization and treated by chemical activation. The carbon electrode materials converted from balsa and pine exhibit a comparable salt adsorption performance by capacitive deionization due to the extensive surface area, substantial electrical property, and superior hydrophilic performance. The following activation treatment of the balsa‐converted carbon further enhances the surface and electrical properties and benefits the desalination performance. The salt adsorption capacity of the activated balsa electrode exhibits 12.45 mg g−1. Additionally, 19.52 mg g−1 Pb2+ and 20.06 mg g−1 Cr3+ heavy metal adsorption capacity is also observed with the activated balsa electrode in 100 mg L−1 PbCl2 and 50 mg L−1 CrCl3, respectively. To the best of authors’ knowledge, this is the highest NaCl adsorption capacity performance reported thus far by using pure wood converted carbon as the electrode, and these promising results indicate that activated balsa is an extraordinary material for water desalination.

Thiol/nitrogen functionalized Fe3O4@ZIF-8-DMTD by one-pot post coordination modulation for efficient and rapid removal of trace heavy metals from drinking water

The deep purification of trace heavy metals in drinking water is of great significance and has received considerable attention worldwide. 2,5-dimercapto-1,3,4-thiadiazole (DMTD) functionalized magnetic ZIF-8 adsorbent (Fe3O4@ZIF-8-DMTD) using a novel one-pot post coordination modulation method at room temperature could effectively adsorb trace heavy metals from drinking water through cooperating with the abundant functional groups and surface charges. The negative surface charges promoted the rapid accumulation of trace heavy metals on the surface of the adsorbent, meanwhile, the abundant thiol/nitrogen sites contributed to their adsorption, thus the adsorption rate and adsorption capacity of trace heavy metals were greatly improved. For trace Pb(II) (150 ppb), the effluent concentration could meet the World Health Organization (WHO) standard (≤10 ppb) within 10 s after adsorption by Fe3O4@ZIF-8-DMTD, and the cumulative adsorption capacity that met WHO standard was 12.11 mg/g. Fe3O4@ZIF-8-DMTD also showed high stability in a broad pH range and excellent adsorption performance in a wide low concentration range. The effluent concentration still could meet the WHO standard when the initial Pb(II) concentration was 11.70 ppm, and the corresponding adsorption capacity reached 35.00 mg/g. Moreover, the capture experiments for multiple heavy metals that coexisted in tap water showed that the effluent concentrations of Hg(II), Pb(II), Cu(II), Cd(II), and Cr(III) could be lower than the allowable limits in a few minutes. The adsorbent could also be easily recovered using magnets and regenerated by thiourea solution, which showed great application potential for the purification of trace heavy metals in drinking water.