Competitive Adsorption Of Heavy Metals Research Articles

Competitive adsorption of heavy metals onto xanthate-modified sludge hydrochar and its solidification as secondary minerals

In this study, a sulfur-modified magnetic hydrochar was synthesized by grafting thiol-containing groups onto the sludge-derived hydrochar. The modified hydrochar exhibited effective adsorption of Cu2+, Pb2+, Zn2+, and Cd2+ over a wide pH range and in the presence of coexisting ions, and showed almost no secondary leaching in three acidic solutions. In the mult-metal ion system, the modified hydrochar exhibited maximum adsorption capacities were 39.38, 105.74, 26.53, and 38.11 mg g−1 for Cu2+, Pb2+, Zn2+, and Cd2+, respectively. However, the binding capacity and adsorption amount of modified hydrochar for metal ions were lower in the mult-metal ion system compared to the unit-metal ion system. Notably, Pb2+ showed a strong inhibitory effect on the adsorption of other heavy metal ions by modified hydrochar due to strong competition for xanthate functional groups. The Pb2+ occupied the xanthate and native functional groups (–OH, –NH2, and Fe–O etc.), leaving only a small amount of adsorption sites for Cu2+, Zn2+ and Cd2+. Simulation results further supported these findings, indicating that Pb2+ had the highest density profiles near the four functional groups, and the density profiles of the four heavy metals near the xanthate functional groups were greater compared to the other three functional groups. Furthermore, the SEM-EDS, TOF-SIMI, and XPS results indicated that modified hydrochar achieved excellent mineral binding mainly through electrostatic interaction, ion exchange, and chelation. Overall, these results highlight the sulfur-modified magnetic hydrochar as a highly efficient adsorbent for heavy metals in environmental applications.

Respective evolution of soil and biochar on competitive adsorption mechanisms for Cd(II), Ni(II), and Cu(II) after 2-year natural ageing

To reveal the respective evolution of soil and biochar on competitive heavy metal adsorption mechanisms after natural ageing, three soils and two biochars were tested in this study. The soil-biochar interlayer samples were buried in the field for 0.5, 1, and 2 years, for which competitive adsorption characteristics and mechanisms of soils and biochars in four systems (Cd, Cd+Ni, Cd+Cu, and Cd+Ni+Cu) were investigated. Results showed that physicochemical properties, adsorption capacity and mechanisms of soils and biochars all changed the most in the first 0.5 years. The properties and adsorption capacity of biochars gradually weakened with the ageing time, meanwhile, those of soils gradually enhanced. After co-ageing with acidic soil for 0.5 years, the Cd(II) adsorption capacity of modified biochar decreased by 86.59% in the ternary system; meanwhile, that of acidic soil increased by 65.52%. The contributions of mineral mechanisms decreased significantly, while non-mineral mechanisms were slightly affected by ageing. This study highlighted that when using biochar to remediate heavy metal-contaminated soils, biochar should be applied at least half a year in advance before planting crops so that biochar can fully contact and react with the soil.

Competitive heavy metal adsorption on pinecone shells: Mathematical modelling of fixed-bed column and surface interaction insights

Pinecone shells are assessed as a cost-effective biosorbent for the removal of metal ions Pb(II), Cu(II), Cd(II), Ni(II), and Cr(VI) in a fixed-bed column. Influent concentration, bed height, and flowrate are studied to improve efficiency. The breakthrough data is well fitted by the Sips adsorption model, suggesting a surface complexation mechanism, with maximum adsorption capacities of 11.1 mg/g for Cu(II) and 66 mg/g for Pb(II).In multimetal solutions, the uptake sequence at breakthrough and saturation is Pb(II) > Cu(II) > Cd(II). Characterization via FTIR and XRD reveals carboxyl and hydroxyl functional groups interacting with metal ions. Ca(II) does not compete with Pb(II), Cu(II), and Cd(II) adsorption, highlighting the ability of pinecone to adsorb heavy metals via surface complexation. Its application in the treatment of industrial effluents containing Cu(II), Ni(II), and Cr(VI) is explored.The study investigates bed media regeneration via eluting adsorbed metal ions with hydrochloric acid solutions. The potential of pinecone shells as an efficient biosorbent for removing toxic metal ions from industrial wastewater is emphasized. These findings enhance our understanding of the adsorption mechanism and underscore the fixed-bed column system's applicability in real-world scenarios, addressing environmental concerns related to heavy metal contamination of industrial effluents.

Fabrication of biocompatible chitosan/graphene based nanocomposite for the competitive adsorption of heavy metal ions from wastewater in binary and ternary systems: Scale-up and upgradation studies

Coexistence of multiple metal ions in the wastewater alters the adsorption behavior compared to single metal ion system using the existing adsorbents which are chemically driven, requires harsh operating conditions and additional energy. The present study evaluates the performance of Chitosan/Graphene based nanocomposite for the competitive adsorption of heavy metals in single, binary and ternary systems. Maximum removal efficiency was 89.35 % (As), 90.41 % (Cu), 93.22 % (Ni), 96.47 % (Cd), 95.45 % (Pb) and 88.65 % (Cr) under optimum conditions (pH 4, Temperature = 25 °C, Equilibrium Time = 90 min, Adsorbent Dosage = 1.25 g and Initial Metal Ion Concentration = 150 mg/L) in a single system. A detailed investigation on the competitive adsorption of Cadmium, Copper, and Chromium ions was performed in binary. Maximum adsorption capacity was 1.55 mg/g and 1.48 mg/g (CuCd); 2.98 mg/g and 3.21 mg/g (CuCr) and 2.21 mg/g and 1.90 mg/g (CdCr system) at 4 mM concentration. The constructed mathematical models accurately forecast the adsorption behavior and shows a good match with the experimental data. Also, fixed-bed column studies were performed for the large-scale upgradation and optimum flow rate and bed height was 1 L/h and 15 cm at 25 °C. The study proposes the fabrication of natural-polymer based composite which can significantly reduce the dependency on synthetic and chemical-based adsorbents which poses severe negative impacts such as high-cost, poor selectivity and rapid saturation due to their low recyclability or sludge generation. Such application can effectively transform wastewater into contamination free water that could be valuable to society.

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.

Effects of Chelating Surfactants on Competitive Adsorption of Lead and Zinc on Loess Soil

The study of competitive adsorption of heavy metals on soil is important for heavy metals contaminated soil remediation. However, there have been few studies on the impact of desorption reagents on heavy metal adsorption in soil. Batch adsorption studies were used to investigate the competitive adsorption mechanism of two heavy metals, Pb and Zn, on a loess soil in the presence of a new chelating surfactant, sodium N-lauroyl ethylenediamine triacetate (LED3A). Results showed that competitive adsorption equilibria of Pb and Zn were reached at 3 and 10 h, respectively. The maximum equilibrium adsorption capacities were 19.55 and 18.35 g.kg-1, respectively. LED3A affected the competitive adsorption kinetics of Pb and Zn by increasing the change in external mass transfer and reducing the change in internal mass transfer. LED3A reduced Pb and Zn adsorption capacities onto the soil through competitive chelation of the heavy metals. The heavy metal chelating ability of LED3A was higher for Zn than for Pb. When its concentration was larger than 5 g.L-1, LED3A showed a significant effect on the competitive adsorption of Pb and Zn. In the competitive system, the effect of Pb concentration on the Zn adsorption capacity was greater than the effect of Zn concentration on the Pb adsorption capacity. LED3A weakened the effect of Pb concentration and enhanced the effect of Zn concentration. LED3A showed a significant potential for efficiently leaching remediation of Pb and Zn co-contaminated soil.

Competitive adsorption of heavy metals in a quaternary solution by sugarcane bagasse – LDPE hybrid biochar: equilibrium isotherm and kinetics modelling

Abstract Sugarcane is a notable crop grown in the tropical region of the world. It is an abundant waste material of the sugar industry which is a low cost and low combustion fuel thus the bagasse can be exploited to manufacture adsorbents for water treatment. Because the presence of contaminants in polluted water is not uniform, pollutant species compete for active sites during the adsorption process. Investigation of the competitive adsorption of Zn(II), Cu(II), Pb(II), and Fe(II) in a quaternary solution using hybrid biochar developed from sugarcane bagasse (SCB) mixed Low-Density Polyethylene (LDPE) and pure SCB biochar is the main aim of this study. The biochar was developed using the retort carbonisation process and characterised via SEM (Scanning Electron Microscopy), BET (Branueur Emmett Teller) analysis, and FTIR (Fourier Transform Infrared Spectroscopy). Both biochar species mixture possessed some orbicular properties with mesoporous heterogeneous superficial morphology. The biomass biochar and hybrid biochar specific surface area are 533.6 m2/g and 510.5 m2/g respectively. For the two used adsorbents, >99% removal efficiency was recorded over the sphere for dosage investigation. Thus, this implies they are capable of removing heavy metals from the aqueous solution simulated. The Langmuir isotherm fitted best in each domain however there was an exception for Pb(II) ions in biomass biochar with the experimental adsorption capacity of ∼ 22 mg/g for the HMs. Based on the correlation coefficient (R 2); the experimental data fitted the pseudo-first-order kinetic model well having a correlation coefficient value of greater than 0.9. The mechanism of adsorption for the HMs was chemisorption. This study has a three-pronged benefit of water treatment, resource conservation, and solid waste utilisation.

Competitive adsorption of heavy metals onto modified biochars: Comparison of biochar properties and modification methods

Various biochars (BCs) have been developed to remove heavy metals contained in road runoff; however, there is insufficient information regarding the competitive adsorption efficiency of modified BC with regard to heavy metals due to a lack of comparative evaluation based on BC properties and modification methods. In this study, three different types of BC (RBC: rice husk, WBC: wood chip, MBC: mixture) were modified following five different methods: acidic, alkaline, oxidic, and manganese oxide (MnOx) and iron oxide (FeOx) impregnation. The changes in the physicochemical and morphological properties of the modified BC were investigated, and the adsorption characteristics of three heavy metals (Cd, Pb, and Zn) under single and mixed conditions were compared and evaluated. The improvements in the BC properties varied for different BC types and modification methods; in particular, alkaline and manganese modification caused substantial the changes in the surface area and functional groups (such as aromatic ring, –OH, and Mn–O groups). The BC prepared by manganese oxide impregnation absorbed a high amount of heavy metals (>9.15 mg/g) even under mixed conditions through cation exchange and surface complexation. The distribution coefficient (Kd) of heavy metals was high in the order of Pb > Cd > Zn; thus, the adsorption of Pb replaced that of Zn in competitive adsorption due to the difference in their affinity to BC. Therefore, the results suggest that BC prepared by manganese oxide impregnation is suitable for removing heavy metals from road runoff, as it maintained high heavy metals adsorption regardless of the BC material, even under competitive conditions.

Competitive adsorption of heavy metals by anaerobic ammonium-oxidizing (anammox) consortia

Anammox-based processes and microbial consortia have drawn extensive attention for their use in high-efficiency wastewater treatment technologies. Metals substantially affect the activity of anammox consortia and the quality of wastewater treatment plant effluent. Here, we explored the role of anammox consortia in terms of metals complexation in both single and multi-metal systems. Adsorption edges of single metal cations indicate that the adsorption preference was in the order: Pb(II) > Cd(II) > Cr(VI). A competitive effect was observed in multi-metal cations systems, with Pb(II) being preferably adsorbed and the degree of adsorption somewhat reduced in the presence of either Cd(II) or Cr(VI), while Cd(II) and Cr(VI) were easily exchanged and substituted by other metals. Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) further suggest that the adsorption of Pb(II) and Cd(II) are as inner-sphere ion-exchange mechanisms, while Cr(VI) adsorption is mainly by outer-sphere complexation. Density functional theory (DFT) calculations highlight that Cd(II) and Pb(II) have different binding sites compared to Cr(VI), and the order of binding energy (Ebd) of three metal cations were Pb(II) > Cd(II) > Cr(VI). These calculations support the adsorption data in that Pb forms more stable complexes with anammox bacterial surface ligands. Surface complexation modelling (SCM) further predicted both the sorption of single metal cations and competitive adsorption of the three metals to anammox consortia, the exception being Cd at higher loadings. The results of this study highlight the potential role of anammox consortia in removing metal cations from wastewater in treatment systems.

Competitive heavy metal adsorption onto new and aged polyethylene under various drinking water conditions

The study goal was to identify factors that influence copper (Cu), iron (Fe), lead (Pb), manganese (Mn), and zinc (Zn) loading on new and aged low-density polyethylene (LDPE) under various drinking water conditions. The applied aging procedure increased LDPE surface area, hydrophilicity and the number of oxygen containing functional groups. Aged LDPE adsorbed up to a 5 fold greater metals than the new LDPE: Cu > Pb, Zn > Mn. Water pH (5.5 to 10.5) significantly altered LDPE surface metal loading. The organic carbon leached from plastic pipes inhibited Cu adsorption (−43.8%), but other metals were less impacted (−5.7% to −9.1%). The addition of free chlorine and corrosion inhibitor retarded metal adsorption to suspended LDPE materials. Overall, by changing water conditions total metal loadings (i.e., Cu, Mn, Pb and Zn) were altered 20.1 to 35.4%. When Fe was present, Cu (−4.0%) and Pb (−4.5%) loadings were reduced, while lesser impacts were found for Mn and Zn. Cu2+, Pb2+ and Zn2+ hydroxides and oxides were identified as the major metal deposit forms on the LDPE surface by XPS. To better predict metal fate in plastic piping systems, plastic surface characteristics, dissolved organics, water pH, hydraulic conditions and microbial growth should be considered.

Competitive adsorption of heavy metals in aqueous solution onto biochar derived from anaerobically digested sludge

Heavy metals often coexist in contaminated wastewater systems and their competitive behavior could affect the adsorption capacity of biochar. Till now, the competitive adsorption of heavy metals by biochar derived from anaerobically digested sludge has never been reported. In this work, biochar from anaerobically digested sludge was synthesized and characterized to explore the competitive behavior of widely co-existed Pb(II) and Cd(II). The mutual effects and inner mechanisms of their adsorption on studied biochar were systematically investigated via single-metal and binary-metals systems. In single-metal system, the biochar exhibited much higher adsorption capacity for Pb(II) compared to that for Cd(II). The maximum adsorption capacities of Pb(II) and Cd(II) based on single-component adsorption isotherm were 0.75 and 0.55 mmoL/g, respectively, which were much higher than those reported biochars from different materials. In binary-metals system, the Cd(II) adsorption on biochar was severely inhibited, while the uptake of Pb(II) was not affected significantly. The results of binary-components adsorption isotherm clearly demonstrated the competitive adsorption between two metals occurred as well as the preference of biochar for Pb(II) compared to Cd(II). FTIR and metal characteristics analysis results revealed that Pb(II) had exactly the same adsorption sites with Cd(II), but Pb(II) has a greater affinity than Cd(II), thereby exhibiting a competitive advantage in the coexisting system.

Kinetics, Thermodynamics, and Competitive Adsorption of Heavy Metals from Water Using Orange Biomass.

Adsorption of heavy metals on modified orange biomass has been studied. This biomass was treated with NaOH and CaCl₂ to improve its adsorption properties. Kinetic and thermodynamic studies of the adsorption of Cd2+, Ni2+, Cu2+, and Zn2+ were performed at different operating conditions, including competitive adsorption studies with binary metallic mixtures. Results show that this adsorption process was endothermic where an ion exchange mechanism played a relevant role. Adsorbent effectiveness decreased in binary solutions, indicating a strong antagonistic adsorption behavior caused by counter-ions. This antagonistic adsorption was highly dependent on the counter-ion type and its concentration. Multicomponent adsorption of Cu2+ ions was not significantly affected by the presence of other metallic counter-ions, whereas the adsorption of Ni2+ could be totally suppressed by the other ions. The modeling of binary adsorption isotherms was successful using the modified Langmuir equation, which outperformed the Ideal Absorbed Solution Theory-Sips and modified Redlich-Peterson models.

Competitive Adsorption of Heavy Metals from Aqueous Solution onto Oxidized Activated Carbon Fiber

In this study, the competitive adsorption of Ni(II)–Pb(II) and Ni(II)–Zn(II) on oxidized activated carbon fiber (ACF-Ox) from aqueous solutions was studied. The experimental competitive adsorption data were interpreted by the following multicomponent adsorption isotherms: non-modified, extended, and modified Langmuir; non-modified and modified Redlich-Peterson; extended Freundlich; and Sheindorf-Rebuhn-Sheintuch. The extended Freundlich multicomponent isotherm best fitted the adsorption data for both systems Ni(II)–Pb(II) and Ni(II)–Zn(II) onto ACF-Ox. The single metal adsorption on ACF-Ox showed that the Ni(II) adsorption capacity was 1.12 times greater than that of Zn(II); however, in the competitive adsorption, the Zn(II) presented an intense antagonism to the adsorption of Ni(II) and Ni(II) to Zn(II) too. The single-adsorption isotherms of Pb(II) and Ni(II) on ACF-Ox revealed that the selectivity of Pb(II) towards ACF-Ox was slightly higher than that of the Ni(II). Nevertheless, in the competitive adsorption, the affinity of Pb(II) towards the ACF-Ox was far greater than that of the Ni(II).

Competitive Adsorption of Heavy Metals from Water using Pumice Supported Nano Scale Zero-Valent Iron

Competitive Adsorption of Heavy Metals from Water using Pumice Supported Nano Scale Zero-Valent Iron

Competitive adsorption of Cd2+, Pb2+ and Ni2+ onto Fe3+-modified argillaceous limestone: Influence of pH, ionic strength and natural organic matters

In present study, the feasibility of applying a natural adsorbent with Fe3+ modification (Fe3+-modified argillaceous limestone, FAL) on the competitive adsorption of heavy metals (i.e., Cd2+, Pb2+ and Ni2+) was evaluated. The current results revealed an efficient adsorption on Cd2+, Pb2+ and Ni2+ in mono-metal system. Further experiments demonstrated a high selectivity of Pb2+ during the competitive adsorption of Cd2+, Pb2+ and Ni2+. The adsorption selectivity of the metal ions followed the order of Pb ≫ Cd > Ni. In addition, both pH and ionic strength are important factors affecting the metal adsorptions. It is interestingly that various NOMs (i.e., humic acid (HA) and glycine (Gly)) exerted different effects on the adsorption behaviors, probably due to the different affinities for Pb2+, Cd2+ and Ni2+ and the redistribution of newly-formed metal-DOM complexes. X-ray photoelectron spectroscopy (XPS) analysis together with X-ray diffraction (XRD) and energy dispersive spectrometer (EDS) analysis revealed that the metal adsorptions were mainly regulated via the synergistic mechanisms of ion exchange by Na+, Ca2+, and Al3+, precipitation to form CdCO3 and Pb2(OH)2(CO3)2, as well as complexes of FAL-OPb and FAL-ONi by hydroxyl groups on the surface of FAL. The application of FAL would be a promising option in leading to an efficient heavy metal removal.

High-resolution insight into the competitive adsorption of heavy metals on natural sediment by site energy distribution

Investigating competitive adsorption on river/lake sediments is valuable for understanding the fate and transport of heavy metals. Most studies have studied the adsorption isotherms of competitive heavy metals, which mainly comparing the adsorption information on the same concentration. However, intrinsically, the concentration of each heavy metal on competitive adsorption sites is different, while the adsorption energy is identical. Thus, this paper introduced the site energy distribution theory to increase insight into the competitive adsorption of heavy metals (Cu, Cd and Zn). The site energy distributions of each metal with and without other coexisting heavy metals were obtained. It illustrated that site energy distributions provide much more information than adsorption isotherms through screening of the full energy range. The results showed the superior heavy metal in each site energy area and the influence of competitive metals on the site energy distribution of target heavy metal. Site energy distributions can further help in determining the competitive sites and ratios of coexisting metals. In particular, in the high-energy area, which has great environmental significance, the ratios of heavy metals in the competitive adsorption sites obtained for various competitive systems were as follows: slightly more than 3:1 (Cu-Cd), slightly less than 3:1 (Cu-Zn), slightly more than 1:1 (Cd-Zn), and nearly 7:2:2 (Cu-Cd-Zn). The results from this study are helpful to deeply understand competitive adsorption of heavy metals (Cu, Cd, Zn) on sediment. Therefore, this study was effective in presenting a general pattern for future reference in competitive adsorption studies on sediments.

Noncompetitive and Competitive Adsorption of Heavy Metals in Sulfur-Functionalized Ordered Mesoporous Carbon.

In this work, sulfur-functionalized ordered mesoporous carbons were synthesized by activating the soft-templated mesoporous carbons with sulfur bearing salts that simultaneously enhanced the surface area and introduced sulfur functionalities onto the parent carbon surface. XPS analysis showed that sulfur content within the mesoporous carbons were between 8.2% and 12.9%. The sulfur functionalities include C-S, C═S, -COS, and SOx. SEM images confirmed the ordered mesoporosity within the material. The BET surface areas of the sulfur-functionalized ordered mesoporous carbons range from 837 to 2865 m2/g with total pore volume of 0.71-2.3 cm3/g. The carbon with highest sulfur functionality was examined for aqueous phase adsorption of mercury (as HgCl2), lead (as Pb(NO3)2), cadmium (as CdCl2), and nickel (as NiCl2) ions in both noncompetitive and competitive mode. Under noncompetitive mode and at a pH greater than 7.0 the affinity of sulfur-functionalized carbons toward heavy metals were in the order of Hg > Pb > Cd > Ni. At lower pH, the adsorbent switched its affinity between Pb and Cd. In the noncompetitive mode, Hg and Pb adsorption showed a strong pH dependency whereas Cd and Ni adsorption did not demonstrate a significant influence of pH. The distribution coefficient for noncompetitive adsorption was in the range of 2448-4000 mL/g for Hg, 290-1990 mL/g for Pb, 550-560 mL/g for Cd, and 115-147 for Ni. The kinetics of adsorption suggested a pseudo-second-order model fits better than other models for all the metals. XPS analysis of metal-adsorption carbons suggested that 7-8% of the adsorbed Hg was converted to HgSO4, 14% and 2% of Pb was converted to PbSO4 and PbS/PbO, respectively, and 5% Cd was converted to CdSO4. Ni was below the detection limit for XPS. Overall results suggested these carbon materials might be useful for the separation of heavy metals.

Stabilized chitosan/Fe(0)-nanoparticle beads to remove heavy metals from polluted sediments.

Sediment contamination by heavy metals has become a widespread problem that can affect the normal behaviors of rivers and lakes. After chitosan/Fe(0)-nanoparticles (CS-NZVI) beads were cross-linked with glutaraldehyde (GLA), their mechanical strength, stability and separation efficiency from the sediment were obviously improved. Moreover, the average aperture size of GLA-CS-NZVI beads was 20.6 μm and NZVI particles were nearly spherical in shape with a mean diameter of 40.2 nm. In addition, the pH showed an insignificant effect on the removal rates from the sediment. Due to the dissolution of metals species into aqueous solutions as an introduction of the salt, the removal rates of all heavy metals from the sediment were increased with an increase of the salinity. The competitive adsorption of heavy metals between the sediment particles and GLA-CS-NZVI beads became stronger as the sediment particles became smaller, leading to decreased removal rates. Therefore, the removal efficiency could be enhanced by optimizing experimental conditions and choosing appropriate materials for the target contaminants.

Competitive adsorption of heavy metals by extracellular polymeric substances extracted from Klebsiella sp. J1

The adsorption of Cu2+ and Zn2+ by extracellular polymeric substances (EPS) extracted from Klebsiella sp. J1 and competitive adsorption mechanism were investigated. Equilibrium adsorption capacities of Cu2+ (1.77mMg−1) on Klebsiella sp. J1 EPS were higher than those of Zn2+ (1.36mMg−1) in single systems. The competitive Langmuir and Langmuir–Freundlich isotherm models were proven to be effective in describing the experimental data of binary component system. The three dimensional sorption surfaces of binary component system demonstrated that the presence of Cu2+ more significantly decreased the sorption of Zn2+, but the sorption of Cu2+ was not disturbed by the presence of Zn2+. FTIR and EEM results revealed the adsorption sites of Cu2+ entirely overlapped with those of Zn2+. Cu2+ and Zn2+ showed competitive adsorption in binary systems, and Cu2+ was preferentially adsorbed because of the stronger complexation ability of the protein-like substances in Klebsiella sp. J1 EPS.

Competitive adsorption of heavy metals onto sesame straw biochar in aqueous solutions

Objective of this research was to evaluate adsorption of heavy metals in mono and multimetal forms onto sesame straw biochar (SSB). Competitive sorption of metals by SSB has never been reported previously. The maximum adsorption capacities (mgg−1) of metals by SSB were in the order of Pb (102)≫Cd (86)≫Cr (65)>Cu (55)≫Zn (34) in the monometal adsorption isotherm and Pb (88)≫Cu (40)≫Cr (21)>Zn (7)⩾Cd (5) in the multimetal adsorption isotherm. Based on data obtained from the distribution coefficients, Freundlich and Langmuir adsorption models, and three-dimensional simulation, multimetal adsorption behaviors differed from monometal adsorption due to competition. Especially, during multimetal adsorption, Cd was easily exchanged and substituted by other metals. Further competitive adsorption studies are necessary in order to accurately estimate the heavy metal adsorption capacity of biochar in natural environments.