Competitive Adsorption Of Lead Research Articles

Competitive adsorption of lead and cadmium onto nanoplastics with different charges: Two-dimensional correlation spectroscopy study.

The competitive adsorption ability and mechanisms of lead (Pb2+) and cadmium (Cd2+) by nanoplastics (NPs) with positive charges (PS-NH2) and negative charges (PS-SO3H) were investigated by using batch adsorption experiments coupled with the two-dimensional correlation spectroscopy (2D-COS) method. The adsorption isotherm results showed that PS-SO3H exhibited a higher adsorption capacity for Pb2+ or Cd2+ compared to PS-NH2. The adsorption affinity of NPs for Pb2+ was higher than that of Cd2+. The competitive adsorption results showed that Pb2+ had a more pronounced negative effect on the adsorption of Cd2+. The adsorption capacities of NPs were affected by the surface charge and solution pH. Electrostatic force was the main factor influencing PS-SO3H to capture Pb2+ and Cd2+, while chelation was the main mechanism between PS-NH2 and metals. The functional groups of NPs played significant roles in the sorption of Pb2+ or Cd2+ according to the FTIR spectra and 2D-COS analysis. This study provided new insights into the impact of NPs on the transport of other pollutants.

Competitive adsorption of lead and cadmium on soil aggregate at micro-interfaces: Multi-surface modeling and spectroscopic studies

Aggregates are the basic structural units of soils and play a crucial role in metal migration and transformation. Combined contamination of lead (Pb) and cadmium (Cd) is common in site soils, and the two metals may compete for the same adsorption sites and affect their environmental behavior. Herein, the adsorption behavior of Pb and Cd on aggregates of two soils and contributions of soil components in single and competitive systems were studied by combining cultivation experiments, batch adsorption, multi-surface models (MSMs), and spectroscopic techniques. The results demonstrated that < 2 µm size aggregate was the dominant sink for Pb and Cd competitive adsorption in both soils. Compared with Pb, the adsorption capacity and behavior of Cd were affected greatly under competition. MSMs prediction revealed that soil organic matter (SOM) contributed the most to Cd and Pb adsorption on aggregates (> 68.4%), but the dominant competitive effect occurred on different sites for Cd adsorption (primarily on SOM) and Pb adsorption (primarily on clay minerals). Further, 2 mM Pb coexistence caused 5.9 − 9.8% of soil Cd conversion to unstable species (Cd(OH)2). Thus, the competitive effect of Pb on Cd adsorption cannot be ignored in soils with high content of SOM and fine aggregates.

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.

Kinetics, thermodynamics and competitive adsorption of lead and zinc ions onto termite mound

The elemental composition of termite mound was determined by XRF which revealed K, Ti and Mn as minor constituents while Ca and Fe as major constituents. The dominant functional groups of termite mound are Fe–OH, Fe–O and O–H. The Pb(II) and Zn(II) adsorption capacities (mg g−1) are in order of Pb(II) (13.07) > Zn(II) (12.40) > Pb(Pb/Zn) (11.72) > Zn(Pb/Zn) (7.62). The Langmuir adsorption isotherm fitted the adsorption data better than Freundlich isotherm. The adsorption process was best described by pseudo-second-order kinetic model for single and binary solutions, and the rate constants k 2 (g mg−1 min−1) are 0.036, 0.016, 0.024 and 0.015, and the calculated value of q e (mg g−1) is 12.33, 12.25, 11.52 and 7.84 for Pb(II), Zn(II), Pb(Pb/Zn) and Zn(Pb/Zn), respectively. The regression coefficient, R 2 values, for these solutions ranged between 0.9966 and 0.9978. The ΔH (kJ mol−1) values were positive for single and binary solutions in the order Pb(II) (32.0) > Pb(Pb/Zn) (30.8) > Zn(Pb/Zn) (28.0) > Zn(II) (19.0), while ΔS (kJ mol−1 K−1) are in the order of Pb(II) (0.103) > Pb(Pb/Zn) (0.097) > Zn(Pb/Zn) (0.082) > Zn(II) (0.06). The ΔG value for Zn(II) is positive in both single and binary systems, while that for Pb(II) was positive between 313–333 and 323–333 K for single and binary systems, respectively. The data show that the use of neglected termite mound for Pb(II) and Zn(II) removal from aqueous solutions is economically significant in wastewater treatment.

Competitive Adsorption of Lead and Copper by Kaolin

Due to the potential of kaolin as an adsorbent for removal of heavy metals from solution, the competitive adsorption of Lead (Pb) and Copper (Cu) by kaolin was investigated to provide further understanding on the binding behaviors and capacities of these two metals onto kaolin. The Langmuir and Freundlich isotherms were applied to further explain the competition between the metals. Three different solutions were used, each at concentrations 10, 20, 30, 45, 60 and 75mg/L: single-metal solution of Pb (Pb-Only), single-metal solution of Cu (Cu-Only), and solution of both metals at the same concentrations (Binary solution). The kaolin adsorbed Pb about twice more than Cu, both for the binary solution and for the single-metal solutions. This correlated well with predictions of maximum adsorption capacity (Q) for kaolin, where Q for Pb was about twice as much as that for Cu, both in the binary solution and in the single-metal solution. Competition from Cu in binary solution reduced Pb adsorption by 9%, while Cu rather increased by 4.1%, relative to their respective adsorptions in Pb-Only and Cu-Only, respectively. However, during competitive adsorption in the binary solution, the relative proportions of adsorbed Pb increased by 11.4% as the initial metals concentration increased from 10 – 75mg/L, while that of Cu reduced by the same proportion. This was explainable by their respective separation factors (RL), which indicated higher favorability of kaolin for Pb than for Cu. Furthermore, bonding energy (KL) of Pb unto kaolin during competition was about 2.5 times that of Cu, and was likely able to cause Pb to displace Cu from kaolin surface. This study reveals greater adsorption capacity of kaolin for Pb than for Cu, and could provide the basis for future projects/studies that would employ kaolin in Pb and Cu removal.

ADSORPTION OF LEAD AND COPPER FROM AQUEOUS SOLUTION USING UNMODIFIED WHEAT STRAW

Abstract Potential of unmodified Wheat Straw as an adsorbent for the removal of lead and copper was studied. Effect of pH, adsorbent dose, contact time and initial metal concentration on the removal of the metal ions were also investigated. Maximum removal of lead was found to be 43.55% by wheat straw under optimum conditions (pH=5, adsorbent dose=16g/L, contact time= 240 minutes, metal concentration=100 mg/L). Unmodified Wheat straw removed 0.381 mg/g of lead. While 56.36% copper removal was achieved using unmodified wheat straw under optimum conditions (pH=5, adsorbent dose=20g/L, contact time= 120 minutes, metal concentration=100 mg/L). Unmodified Wheat Straw removed 0.587 mg/g of copper. Langmuir isotherm was found to validate the equilibrium data of adsorption while kinetics were described by pseudo second order rate equation for both the metals.Furthermore, competitive adsorption of lead and copper showed that lead had more affinity for Wheat Straw as compared to copper. It was concluded that removal efficiency of unmodified Wheat Straw is much less as compared to modified Wheat Straw.

Competitive adsorption of lead and zinc from aqueous solution on activated carbon prepared from Van apple pulp: Study in single- and multi-solute systems

The potential of activated carbon (VAAC) prepared from local agricultural waste, apple pulp, as an alternative low-cost adsorbent was investigated for the removal of lead and zinc from single- and multi metal aqueous solution. VAAC was produced with a reasonable yield, 43% and has remarkable surface area (1067.01m2/g) with a well-developed pore structure. To determine the adsorption process and properties, the effects of various operating parameters, pH of the solutions (2–6), adsorbent dosage (0.01–0.2g), initial concentration of metal ions (25–40mg/L), contact time (3–120min) and temperature (298–308K) were investigated in a batch adsorption technique. The adsorption isotherm data were better fitted by Langmuir model. The pseudo second-order model was found more applicable to describe the kinetic of system in both the single- and multi-solute system. The adsorption capacities of heavy metals decrease in the order of Pb(II) (15.96mg/g)<Pb (Pb+Zn) (13.23mg/g)<Zn(II) (11.72mg/g)<Zn (Pb+Zn) (7.54mg/g) at 298K. Although individual metal ions adsorption decreases in multi-system, the more metal ions are adsorbed (20.77mg/g). The intraparticle diffusion model, external mass transfer coefficient, film and pore diffusion coefficient at different temperatures were also evaluated to investigate the adsorption mechanisms of both systems. The adsorption was mainly controlled film diffusion process at all operating temperatures and concentrations. The thermodynamic parameters indicate that the adsorption process is endothermic, feasible and thermodynamically favored.

Competitive Adsorption of Lead, Copper and Zinc Ions on Polymeric Al/Fe Modified Clinoptilolite

The individual and competitive adsorption capacities of Pb2+, Cu2+ and Zn2+ on clinoptilolite and polymeric Al/Fe modified clinoptilolite were studied. In single systems, adsorption capacity of Pb2+ exceeded that of Cu2+ and Zn2+, and the adsorption capacities of Pb2+, Cu2+ and Zn2+ by polymeric Al/Fe modified clinoptilolite were greater than clinoptilolite. In binary isometric competition adsorption, adsorption capacities of Pb2+, Cu2+ and Zn2+ by clinoptilolite and polymeric Al/Fe modified clinoptilolite decreased compared with single systems. In binary non -isometric competition adsorption, adsorption of Zn2+ from solutions containing a fixed Zn2+ concentration was severely depressed (34%, 26% by clinoptilolite and polymeric Al/Fe (PAFC) modified clinoptilolite, respectively) by increasing the concentration of Cu2+ in the solution, but inverting the roles of Cu2+ and Zn2+ caused only a relatively minor reduction in adsorption of Cu2+. What,s more in other non-equal competition binary systems, the effect of metal adsorption was little. In general, the strength of adsorption followed the order of Pb2+ &gt; Cu2+ &gt; Zn2+ and the order of PAFC modified clinoptilolite &gt; clinoptilolite.