Heavy Metal Adsorption Capacity Research Articles

High-efficiency electrochemical removal of Cd(II) from wastewater using birnessite-biochar composites: Performance and mechanism.

Birnessite has been widely used for electrochemical removal of heavy metals due to its high pseudocapacitance. Incorporation of carbon-based materials into birnessite can enhance its conductivity and stability, and synergistically improve the electrochemical adsorption capacity due to the double-layer capacitor reaction derived from carbon-based materials. In this study, biochar was successfully incorporated with birnessite at various ratios to synthesize composites (BC-Mn) for effective electrochemical removal of cadmium (Cd(II)) from water. The effects of cell voltage, initial pH, and recycling performance of BC-Mn were evaluated. As a result, the electrosorption capacity of BC-Mn for Cd(II) exhibited gradual increases with increasing birnessite content and reached equilibrium at a Mn content of 20% (BC-Mn20). The Cd(II) adsorption capacity of BC-Mn20 rose at higher cell voltage, and reached the maximum at 1.2V. At pH 3.0-6.0, the electrosorption capacity initially rose until pH 5.0 and then approached equilibrium with a further increase in pH value. The Cd(II) electrochemical adsorption capacity of BC-Mn20 in the solution could reach 104.5mgg-1 at pH 5.0 for 8h at 1.2V. Moreover, BC-Mn20 exhibited excellent reusability with a stability of 95.4% (99.7mgg-1) after five cycles of reuse. Due to its superior heavy metal adsorption capacity and reusability, BC-Mn20 may have a promising prospect in the remediation of heavy metal polluted water.

Feasible synthesis of magnetic zeolite from red mud and coal gangue: Preparation, transformation and application

A feasible synthesis of magnetic zeolite from the mixture of industrial solid wastes (red mud and coal gangue) was proposed. The preparation conditions, formation mechanism and adsorption performance of magnetic zeolite were investigated. Magnetic zeolite with uniform distribution of zeolite and magnetite could be successfully synthesized at the alkali reducing calcination conditions of n(Na:Al:Si) = 3.6:1:1, 600 °C, 1.5 h and the hydrothermal conditions of n(Na:H2O) = 2.8:1, 90 °C, 9 h. During this process, aluminosilicates in the mixture of red mud and coal gangue could be transformed into sodium-containing phases and zeolite A in turn; meanwhile, hematite in red mud could be reduced by carbon in coal gangue to transform into magnetite. The prepared magnetic zeolite showed excellent adsorption capacity and reusability for heavy metals. The maximum adsorption capacity for Cu2+, Cd2+ and Pb2+ reached 76.2, 92.2 and 178.4 mg/g, respectively, which could be attributed to the different ionic radius of heavy metals.

Competitive adsorption of heavy metals between Ca–P and Mg–P products from wastewater during struvite crystallization

Wastewater usually contains high concentration of calcium (Ca), posing a competitive reaction with magnesium (Mg) on phosphorus (P) recovery during the struvite crystallization. The differences in the adsorption of heavy metals by Ca–P and Mg–P (struvite) generated are still unclear. Herein, we analyzed the residues of four kinds of common heavy metals (Cu, Zn, Cd, Pb) in Ca–P and Mg–P (struvite) under varying conditions (solution pH, N/P ratio, Mg/Ca ratio) in the swine wastewater and explored their possible competitive adsorption mechanisms. The experiments using synthetic wastewater and real wastewater have similar experimental patterns. However, under the same conditions, the metal (Pb) content of struvite recovered from the synthetic wastewater (16.58 mg/g) was higher than that of the real wastewater (11.02 mg/g), as predicted by the Box-Behnken Design of Response Surface Methodology (BBD-RSM). The results demonstrated that Cu was the least abundant in the precipitates compared to Zn, Cd, and Pb of almost all experimental groups with an N/P ratio greater than or equal to 10. The fact might be mainly attributed to the its stronger binding capacity of Cu ion with NH3 and other ligands. Compared with struvite, the Ca–P product had a higher adsorption capacity for heavy metals and a lower P recovery rate. In addition, the higher solution pH and N/P ratio were favorable to obtain qualified struvite with lower heavy metal content. It can be applied to reduce the incorporation of heavy metals by modulating pH and N/P ratio through RSM, which is suitable for different Mg/Ca ratios. It is anticipated that the results obtained would offer support for the safe utility of struvite from wastewater containing Ca and heavy metals.

Adsorption of heavy metals from mine wastewater using amino-acid modified Montmorillonite

This study was conducted to identify the ability of a modern developed amino-acid modified montmorillonite clay (AA-Mont) to adsorb Cu2+, Pb2+ and Ni2+ cations from a multi-aqueous wastewater. This experimental was conducted to identify the potential of clay-based adsorbents to remediate pollutants from the PRA river basin. Experimental wastewater was prepared using a range of the lowest and highest recorded upstream and downstream heavy metal concentrations of u2+(10.84 mg/L-108.48 mg/g), Ni2+(7.99 mg/g–79.92 mg/g), and Pb2+(33.538 mg/L—335.38 mg/L). The variants of the designed clay-based adsorbents were L-Cysteine montmorillonites (Cys-Mont), Glycine montmorillonite (Gly-Mont), and L-lysine Montmorillonites (Lys-Mont) prepared at pH 4, 5, and 6 respectively. The experimental conditions were; Adsorbent dosages range = 25 mg–400 mg, pH = 6.0, Contact time = 24 hrs, Temperature = 25°C and Shaker speed = 180 rmp. After the adsorption experiments, it was identified that the maximum average removal efficiency obtained for Cu2+, Ni2+, and Pb2+ were all attained at adsorbent dosage 400 mg/L and in the order Lys-Mont (99.82%)>Cys-Mont (99.28%)>Gly-Mont (95.8%). Thus, the modified Lys-Mont clay exhibited the highest heavy metal adsorption capacity amongst the above three studied. The highest and lowest adsorbed metal pollutants amounts recorded for Lys-Mont were Cu2+ (86.49 and 8.65) mg/g, Ni2+ (44.51 and 5.99) mg/g, and Pb2+ (267.85 and 26.67) mg/g respectively. The number of metal ions adsorbed per unit mass for each metal cation tested decreased with increasing adsorbent dosage. The general order of selectivity documented for all the AA-Monts in this study was Pb>Cu>Ni which is similar to the levels in the prepared wastewater solution (Pb>Cu>Ni). The findings of this study have shown that heavy metal polluted river basins can remediated given the right conditions of temperature, adsorbent dosage, pH and agitation speed.

Modified Shrimp-Based Chitosan as an Emerging Adsorbent Removing Heavy Metals (Chromium, Nickel, Arsenic, and Cobalt) from Polluted Water

Water quality is under constant threat worldwide due to the discharge of heavy metals into the water from industrial waste. In this report, we introduce a potential candidate, chitosan, extracted and isolated from shrimp shells, that can adsorb heavy metals from polluted water. The waste shrimp shell chitosan was characterized via Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS). The adsorption capacity of heavy metals on the modified shrimp shell was measured using an inductively coupled plasma mass spectrometry before and after adsorption. The highest adsorption of arsenic, nickel, and cobalt was 98.50, 74.50, and 47.82%, respectively, at neutral pH, whereas the highest adsorption of chromium was 97.40% at pH 3. Correspondingly, the maximum adsorption capacities of MSS for As, Cr, Ni, and Co were observed to be 15.92, 20.37, 7.00, and 6.27 mg/g, respectively. The application of Langmuir and Freundlich isotherm models revealed that the adsorption processes for the heavy metals were statistically significant (r2 > 0.98). The kinetic studies of metal adsorption, using modified shrimp shell, were well explained by the pseudo-second-order kinetic model with linear coefficients (r2) of >0.97. The presence of a greater number of functional groups on the adsorbent, such as N–H coupled with H–O, –COO−, C–H, N–N, and C–O–C, was confirmed by FTIR analyses. Furthermore, SEM-EDX analysis detected the presence of elements on the surface of modified shrimp shell chitosan. This noteworthy adsorption capacity suggests that MSS could serve as a promising, eco-friendly, and low-cost adsorbent for removing toxic heavy metals including Cr, Ni, As, and Co and can be used in many broad-scale applications to clean wastewater.

Waste to resource: Utilization of waste bagasse as an alternative adsorbent to remove heavy metals from wastewaters in sub-Saharan Africa: A review

AbstractHeavy metals pollution of both surface and groundwater sources of sub-Saharan Africa is alarmingly increased due to unplanned urban populations. Inadequate policies for water management, political commitment, and financial resources forced 65% of rural communities of sub-Saharan Africa to live in economic water stress areas. Sugarcane bagasse (SCB) shows high heavy metals (HMs) adsorption capacity (20–700 mg/g) through chemical entrapments to carbon-oxygen containing functional group and interior pore filling of porous surface. Various modifications like a physical/thermal, chemical, and composite form of bagasse show better adsorption performance for HMs removal. Kinetic and isotherm studies of HMs adsorption equilibrium data over SCB show that both Langmuir and Freundlich adsorption isotherms (cooperative adsorption) as the main adsorption mechanism. In addition, SCB shows potential bio-adsorbent properties for the selective adsorption of target HMs based on their physicochemical properties and shows good repeatability in acid environments. It is believed that information on this review will shed light on the current and future prospects of raw and modified SCB for HMs adsorption removal capacity. Sugarcane bagasse shows a remarkable selectivity for HMs adsorption removals based on their physicochemical properties and shows good potential capability for future utilizations in real wastewaters of developing countries.

Runoff regulation and nitrogen and phosphorus removal performance of a bioretention substrate with HDTMA-modified zeolite

As a commonly used material in bioretention substrates, natural zeolite (NZ) provides decent adsorption capacity for cation pollutants and heavy metals, but limited ability to remove anion pollutants. Hexadecyltrimethylammonium bromide (HDTMA)-modified zeolite (MZ) was used as the bioretention substrate material. The performance of the media including runoff reduction, nitrate nitrogen (NO3−-N) removal, ammonium nitrogen (NH4+-N) removal, and total phosphorus (TP) removal was assessed by the column experiment. The effects of different levels of modification, ratio of zeolite in the substrate, and rainfall intensity on media performance were investigated. The results indicate that HDTMA-modified zeolite significantly improves the NO3−-N (up to 38.2 times of NZ) and TP (up to17.5 times of NZ) removal rate of media and slightly increases the NH4+-N (up to 1.5 times of NZ) purification performance of the substrate. Compared with the media with NZ, decline on both runoff volume reduction (maximum decline up to 32.9%) and flow rate reduction (maximum decline up to 29.9%) of the media with MZ were observed. Based on multiple regression analysis, quantitative relationship models between influencing factors and response variables were established (R2 > 0.793), the level of the effect of influencing factors on response variables was investigated, and the interactions between influencing factors were explored. The main effect analysis found that the degree of modification affects NO3−-N and TP removal rate of the substrate the most, and when the amount of HDTMA molecules loaded on the zeolite surface exceeds 0.09meq/g, the modification can no longer improve NO3−-N removal efficiency.

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.