Increase In Metal Ion Concentration Research Articles

Biosorption of zinc(II) on rapeseed waste: Equilibrium studies and thermogravimetric investigations

The removal of heavy metals from aqueous effluents so as to avoid their toxic, bioaccumulation and biomagnification effects to humans and environment is usually realized by means of physical, chemical treatment, and biological processes. The aim of this study is to evaluate the potential of rapeseed waste from biodiesel production as a biosorbent for Zn(II) ions.The ability of the rapeseed waste for Zn(II) biosorption exhibited a maximum at pH 4.5–5. The removal efficiency of Zn(II) from solution with an initial concentration of 72mgL−1 varied from 39% to 89% for an increase of the rapeseed waste dose from 2 to 30gL−1. The amount of Zn(II) retained on the tested rapeseed increased with increasing metal ion concentration, but the Zn(II) sorption percentage decreased. The equilibrium data are fitted to the Langmuir isotherm better than to the Freundlich isotherm. The kinetics of Zn(II) biosorption process follows a pseudo-second order model. The thermal stability of the rapeseed before and after Zn(II) biosorption was studied by thermogravimetric analysis. It was found that the zinc loaded rapeseed exhibits a better initial thermal stability than the original rapeseed, presumably due to the cross linking generated by the intermolecular complexation of Zn(II) ions. In both cases, the thermal decomposition takes place according to some reassembling kinetic models, in two phases with order n reactions. The results of this study strongly suggest the possibility to use rapeseed as an effective biosorbent for Zn(II) ions removal from aqueous effluents (municipal/industrial wastewaters).

Valorization of olive stone and sugar cane bagasse by-products as biosorbents for the removal of cadmium from aqueous solution

Olive stone and sugar cane bagasse by-products were used as effective and green biosorbents for the removal of cadmium from aqueous solutions. The efficiency of the biosorbents was characterized by, FTIR, BET, SEM and zeta potential analysis. The effect of pH, initial concentration of Cd2+, contact time and temperature on the adsorption was studied. Both olive stone and bagasse exhibit the highest Cd2+ uptake capacity at a temperature of 298K and initial pH value of 7. For both biosorbents, the equilibrium uptake increased with increasing metal ion concentration with a maximum removal capacity of 96%. Pseudo-second-order adsorption kinetic model satisfactorily simulates the adsorption behavior of Cd2+. The result shows the high potential of using olive stone and sugar cane bagasse by-products as green and inexpensive biosorbents for the removal of cadmium and for the wastewater treatment.

Functionalized nanostructured silica by tetradentate-amine chelating ligand as efficient heavy metals adsorbent : Applications to industrial effluent treatment

Organofunctionalized nanostructured silica SBA-15 with tri(2-aminoethyl)amine tetradentate-amine ligand was synthesized and applied as adsorbent for the removal of Cu2+, Pb2+, and Cd2+ from both synthetic wastewater and real paper mill and electroplating industrial effluents. The prepared materials were characterized by XRD, N2 adsorption-desorption, TGA, and FT-IR analysis. The Tren-SBA-15 was found to be a fast adsorbent for heavy metal ions from single solution with affinity for Cu2+, Pb2+, than for Cd2+ due to the complicated impacts of metal ion electronegativity. The kinetic rate constant decreased with increasing metal ion concentration due to increasing of ion repulsion force. The equilibrium batch experimental data is well described by the Langmuir isotherm. The maximum adsorption capacity was 1.85 mmol g−1 for Cu2+, 1.34 mmol g−1 for Pb2+, and 1.08 mmol g−1 for Cd2+ at the optimized adsorption conditions (pH=4, T=323 K, t=2 h, C0=3 mmol L−1, and adsorbent dose=1 g L−1). All Gibbs energy was negative as expected for spontaneous interactions, and the positive entropic values from 103.7 to 138.7 J mol−1 K−1 also reinforced this favorable adsorption process in heterogeneous system. Experiment with real wastewaters showed that approximately a half fraction of the total amount of studied metal ions was removed within the first cycle of adsorption. Hence, desorption experiments were performed by 0.3M HCl eluent, and Tren-SBA-15 successfully reused for four adsorption/desorption cycles to complete removal of metal ions from real effluents. The regenerated Tren-SBA-15 displayed almost similar adsorption capacity of Cu2+, Pb2+, and Cd2+ even after four recycles. The results suggest that Tren-SBA-15 is a good candidate as an adsorbent in the removal of Cu2+, Pb2+, and Cd2+ from aqueous solutions.

Role of Divalent Metals in Polymer Degradation

The role of divalent metals in the degradation of the physico-mechanical properties of radiation-vulcanized natural rubber latex (RVNRL) films was investigated. RVNRL films were prepared by the addition of metals (Cu, Mg, etc.) of different concentrations (0–30ppm) to natural rubber latex and irradiated with various radiation doses (0–20kGy). The radiation doses were optimized (12kGy), and the adverse effect of metal ions was studied against a reference film prepared with no metal ions. Tensile strength, tear strength, and cross-linking density of the irradiated rubber films decreased with increasing metal ion concentrations and decreasing radiation doses. The mechanical properties of the films were reduced by 10–15% for 30ppm metal ions and at the optimum dose. In contrast, elongation at break, permanent set, and swelling ratio of the films increased at the same conditions. The relative effect of metal ions can be explained by the classical electron concept, reported in this article.

Adsorptive capacity of polyacrylonitrile modified with triethylenetetramine for removal of copper and cadmium ions from aqueous solutions

A simple method was developed for modification of polyacrylonitrile with triethylenetetramine (PAN‐TETA) as absorbent of copper and cadmium ions. PAN‐TETA and its metal complexes were characterized by FT‐IR and SEM. FT‐IR studies confirmed the presence of metal ions in the metal‐PAN‐TETA complexes. The obtained aminated polyacrylonitrile was evaluated for chelating of Cu(II) and Cd(II) ions. Batch adsorption studies were carried out on the effect of experimental parameters including pH, amount of adsorbent, contact time, initial concentration of metal ions, and temperature. Adsorption efficiency increased with increasing metal ions concentration, initial pH, and temperature. The adsorption kinetics followed pseudo‐second‐order kinetic model with correlation coefficients of 0.999. Experimental data were analyzed by model equations such as Langmuir and Freundlich isotherms. It was found that Langmuir isotherm model was better fitted with the adsorption data. The maximum sorption capacity of 109.26 and 99.67 mg g−1 for copper and cadmium ions were achieved in pH = 6, respectively. The negative value of ΔGº indicated the spontaneous nature of the adsorption. The competitive tests verified that PAN‐TETA had good adsorption selectivity for Cu (II) with the coexistence of copper and cadmium ions. © 2013 American Institute of Chemical Engineers Environ Prog, 33: 1139–1147, 2014

High capacity removal of silver(I) and lead(II) ions by modified polyacrylonitrile from aqueous solutions

Different polymeric materials carrying synthetic adsorbents have been reported in literature for heavy metal removal. We have developed a simple method for functionalizing of polyacrylonitrile (PAN) with two volume percent (50 and 100) of triethylenetetramine (PAN–TETA 50 and 100). For the first time, PAN–TETA was used as an absorbent of silver and lead ions from aqueous solutions. PAN–TETA and their metal complexes have been studied by FT-IR and scanning electron microscope. The analysis method confirmed the presence of metal in PAN–TETA complexes. The prepared functionalized PAN were applied to remove heavy metal ions, such as Pb(II) and Ag(I) from aqueous solutions. The optimization of experimental conditions and parameters including initial pH, contact time, adsorbent dose, initial metal and ions concentration, and temperature for the removal of heavy metals were investigated. The adsorption increased with increasing metal ions concentration, initial pH, and temperature. Pseudo-first-order, pseudo-second-order, and intraparticle diffusion models were considered to evaluate the rate parameters. The adsorption followed pseudo-second-order kinetic model with correlation coefficients greater than 0.997. Attempts were made to fit the isothermal data using Langmuir, Freundlich, and Temkin equations. The maximum sorption capacity of 108.14 mg g−1 and 99.01 mg g−1 for silver and lead ions were achieved at pH = 6, respectively. The values of thermodynamic parameters of ΔG°, ΔH,° and ΔS° indicated that the adsorption process was spontaneous and endothermic. The selectivity of two PAN–TETA for the adsorption of Ag(I) and Pb(II) were studied. The competitive adsorption tests verified that these functionalized polymers have good adsorption selectivity for Ag(I) with the coexistence of two ions. Desorption of the metal ions from PAN–TETA was studied in 0.5M HCl and very high desorption rates, greater than 91%, were achieved in all cases. Based on adsorption/desorption data, PAN–TETA is a promising adsorbent for heavy metals removal from the aqueous medium.

On the use of imidazolium and ammonium-based ionic liquids as green solvents for the selective recovery of Zn(II), Cd(II), Cu(II) and Fe(III) from hydrochloride aqueous solutions

This work analysed the extraction of Zn(II), Cd(II), Cu(II) and Fe(III) from hydrochloride aqueous solutions using imidazolium and ammonium-based ionic liquids as sole extraction agents. The selective separation of the different species is desired for potential valorization of aqueous effluents in which these ions are involved, for example, in zinc refineries. The influence of parameters affecting the extraction of the target metal ions, such as the ionic liquid composition, metal ion concentrations and hydrochloric acid concentration in the aqueous phase was analysed. It was found that the ionic liquid methyltrioctylammonium chloride [MTOA+][Cl−] allowed almost the complete removal of Zn(II), Cd(II) and Fe(III) from the aqueous solutions while the use of 1-methyl-3-octylimidazolium tetrafluoroborate [omim+][BF4-] allowed the selective separation of Zn(II) and Cd(II) over Fe(III) and Cu(II). An increase in metal ion concentration decreases the extraction percentage of the assayed metal ions. The initial HCl concentration has also an important effect on the efficiency of the extraction process, founding that an increase in HCl concentration involves a significant increase in the extraction percentages for Zn(II), Cd(II) and Fe(III). This work demonstrates the exciting potential of ionic liquids for use as green extraction agents in liquid/liquid extraction of heavy metal ions.

Effect of surface modification of microfiltration membrane on capture of toxic heavy metal ions

A novel complexing membrane containing 8-hydroxyquinoline groups was used for the removal of heavy metal ions (Cd2+ and Ni2+) from aqueous solution. The functionalized membranes were characterized by FTIR–ATR, SEM and EDAX for the presence of functional groups, the physical structure of the membranes and the analysis of the particles deposited on the membrane, respectively. The influence of 8-hydroxyquinoline concentration, feed concentration, pH and temperature of the solution on capture capability was studied. The modified membrane showed a higher affinity to Cd2+ cations than to Ni2+. The metal ion rejection was increased with an increase in concentration of 8-hydroxyquinoline from 0.5 to 2.0 wt%. However at a ligand concentration higher than 2.0 wt%, no significant change was observed in the metal rejection. The experimental results revealed that the metal rejection was decreased with an increase in metal ion concentration in the feed. Moreover the rejection depended on feed pH and is higher for elevated pH. By changing the temperature in the range of 23–28 °C, no considerable effect on metal rejection was observed. However, a higher temperature resulted in a decline in metal rejection. For filtration of a mixture of the two metal ions, the retention was similar to that of the single cations, i.e. Cd>Ni but with smaller absolute rejections.

Preparation of a Modified PTFE Fibrous Photo-Fenton Catalyst and Its Optimization towards the Degradation of Organic Dye

Polytetrafluoroethylene (PTFE) fiber was grafted with acrylic acid to impart the carboxyl groups onto the fiber surface, which were used to coordinate with both transition metal ions Fe(III) and Cu(II) and a rare metal ion Ce(III) to prepare the metal grafted PTFE fiber complexes as the novel heterogeneous Fenton catalysts for the degradation of the azo dye in water under visible irradiation. Some factors affecting the preparation process, such as nature and concentration of metal ions in the coordination solution, grafting degree of PTFE and reaction temperature were optimized with respect to the content and strength of metal fixation on the fiber and dye degradation efficiency. The results indicated that increasing metal ion concentrations in solution and grafting degree of PTFE fiber as well as higher coordination temperature led to a significant increase in metal content, especially Fe(III) and Cu(II) content of the complexes. Fe(III) ions fixed on the fiber showed the better catalytic performance than Cu(II) and Ce(III) ions fixed when three different complexes with similar metal content being employed, respectively. Moreover, Increasing Fe content or incorporation of Cu(II) ions could significantly improve the catalytic activity of the complexes.

Efficacy of physically pretreated Mangifera indica biomass for Cu2+ and Zn2+ sequestration

To develop a strategy for the eradication of Cu2+ and Zn2+ from contaminated waters, the waste biomass of Mangifera indica was pretreated physically (autoclaved, boiled and heated) for assessing the uptake capacity of native and pretreated biomass for Cu2+ and Zn2+ biosorption on batch scale, concentrating on pH, pretreatment, biosorbent dose, metal concentration, contact time and temperature as operational parameters. To measure the goodness-of-fit error functions as sum of square error (SSE), chi-square (χ2) and residual root mean square error (RMSE) were used. Best results were obtained at pH 5 (80.65 mg/g) and 6 (94.25 mg/g) for Cu2+ and Zn2+, respectively, with autoclaved leaves. Sorption capacity of biomasses was found to be decreased with increase in biosorbent dose and temperature while it increased with increase in metal ion concentration and with time. Freundlich isotherm was found favorable to describe sorption mechanism, whereas pseudo-second-order kinetic model was best employed to describe sorption rate.

Flocculating activities of polysaccharides released from the marine mat-forming cyanobacteria Microcoleus and Lyngbya

AB Aquatic Biology Contact the journal Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections AB 11:243-248 (2011) - DOI: https://doi.org/10.3354/ab00309 Flocculating activities of polysaccharides released from the marine mat-forming cyanobacteria Microcoleus and Lyngbya Li Chen1,2, Tianli Li1, Liang Guan1, Yawei Zhou1, Pengfu Li1,* 1State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, Nanjing 210093, PR China 2Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, PR China *Email: pengfuli@nju.edu.cn ABSTRACT: Mat-forming cyanobacteria of the genera Microcoleus and Lyngbya were isolated from the Tainan Saltworks, China. The released polysaccharides (RPSs) from the 2 cyanobacterial isolates flocculated kaolin clay from suspensions, and this flocculating activity decreased with increasing pH from 3 to 10.5. The flocculating activities increased with increasing metal ion concentrations and reached plateaus when the concentrations of monovalent cations (Na+ or K+) and divalent cations (Mg2+ or Ca2+) increased to 0.4 and 0.2 mol l–1, respectively. Compared with the previously reported data about the flocculating activities of exopolysaccharide from the freshwater cyanobacterium Phormidium J-1, the presence of higher concentrations of metal ions was required for the flocculating activities of the RPSs from the 2 marine cyanobacteria studied here. The production of extracellular bioflocculants by the benthic cyanobacteria could be of considerable importance in the flocculation and sedimentation of clay particles in brines, which in turn would allow light to penetrate to the sediment–water interface. KEY WORDS: Flocculating activity · Released polysaccharide · Marine cyanobacteria · Microcoleus sp. · Lyngbya sp. Full text in pdf format PreviousNextCite this article as: Chen L, Li T, Guan L, Zhou Y, Li P (2011) Flocculating activities of polysaccharides released from the marine mat-forming cyanobacteria Microcoleus and Lyngbya. Aquat Biol 11:243-248. https://doi.org/10.3354/ab00309 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AB Vol. 11, No. 3. Online publication date: January 25, 2011 Print ISSN: 1864-7782; Online ISSN: 1864-7790 Copyright © 2011 Inter-Research.

Sorption of homologues of radionuclides by synthetic ion exchanger

Present work describes sorption of homologues of radionuclides ( UO 2 2 + , Th 4+, Eu 3+, Sm 2+, Ru 3+ and Fe 3+) on synthesized ion exchangers (analogues of nepheline, marialite and natrolite). The study was investigated by batch technique and three different series of experiments were carried out on different ion exchangers at various parameters such as effect of time (3–24 h), pH (1–9), sorbent concentration (2–10 g/L), metal ion concentration (0.05–0.001 M), temperature (30–50 °C) and effect of competing ions (Na +, K +, Mg 2+ and Ca 2+). Time of equilibration was found to be 7 h which indicates fast kinetics between the sorbent and sorbate. Sorption was observed to be pH dependent. Sorption was enhanced by increasing the sorbent dose and reduced by increasing metal ion concentration. Thermodynamic study indicates the spontaneous, entropy favorable and endothermic nature of sorption process. Sorption was found to be affected in the presence of competing cations and was observed that it reduced with increase in the concentration of competing cations in the suspension which may be probably due to the competition between these ions and desired metal ion for the sorption. Desorption study showed that organic leachants have greater desorption capacity than water.

Pre-treatment of desalination feed seawater by Jordanian Tripoli, Pozzolana, and Feldspar: Batch experiments

In this research, composites of layered double hydroxide (LDH) with three Jordanian natural raw materials; Tripoli (T), Pozzolana (P) and Feldspar (F) were prepared by co-precipitation and have been used for feed seawater pre-treatment. The data reveals that percent adsorption decreased with increase in initial concentration, but the actual amount of adsorbed ions per unit mass of LDH/T-P-F increased with increase in metal ion concentrations. The values of ?Go were negative and within 21 to 26 KJ/mol, while the values of ?Ho and ?So were positive and within the range of 0.1 to 25 KJ/mol. The values of ?H?, ?S?, and ?G? indicate the favorability of physisorption and show that the LDH/T-P-F composites have a considerable potential as adsorbents for the removal of ions from seawater.

Effect of humic acid on sorption of trace metal ions by sodium aluminosilicate

Sorption of trace metal ions (Pb 2+, Zn 2+ and Hg 2+) on synthesized sodium aluminosilicate (Na–AS), an important clay mineral, was carried out in the presence and absence of humic acid (Aldrich) at different pH (3 to 10). The material was synthesized by solution route method and it was characterized by using different techniques such as X-ray diffraction, FT-IR, zeta potential measurement, BET surface area analysis and site density measurement. A series of experiments were made to find out the effect of ionic strength, calcium ions, sorbent dose, metal ions concentration and temperature on the sorption of divalent metal ions by Na–AS. The sorption was found to be dependent on pH as well as humic acid. At lower pH (< pH 6) sorption was observed to be enhanced in the presence of humic acid. Ionic strength played an important role in the sorption of metal ions. Sorption was observed to be decreased with increase in metal ion concentration (10 −5 M to 10 −2 M) and data was fitted well in Freundlich isotherm. Thermodynamic study showed endothermic, entropy favorable and spontaneous sorption behavior of metal ions by sodium aluminosilicate.

Removal of heavy metal ions from aqueous solutions by a local dairy sludge as a biosorbant

In this work, the removal of lead and cadmium from an aqueous solution by a local dairy sludge was investigated in a batch system. Biosorption of these heavy metals was studied as a function of solution initial pH, equilibrium time, temperature, biosorbent dose, biosorbent particle diameter and initial metal ion concentration. Maximum sorption was observed at a pH value of 5 and a temperature of 40 °C. Equilibrium uptake increased with increasing metal ion concentration for both metals with a maximum sorption capacity of a 148.6 mg/g for Pb (II) and 66.7 mg/g for Cd(II). The Langmuir model was found to better describe the sorption of lead ions with a correlation factor of 0.99 while Freundlich and Temkin models were better for Cd(II) sorption. The temperature increase from 20 to 40 °C enhanced the uptake of Pb(II) by 20% and Cd(II) by 5%. The sorption kinetics were compatible with the pseudo-second order model for the systems investigated. SEM micrographs were determined before and after sorption. Nitric and hydrochloric acids were used for the metals desorption. Pb(II) was better desorbed by nitric acid whereas Cd(II) was eluted slightly better by chlorhydric acid.

Transport of metal ions across an electrically switchable cation exchange membrane based on polypyrrole doped with a sulfonated calix[6]arene

The conducting polymer polypyrrole, PPy, was used as the active component of a cation exchange membrane for transferring a range of metal ions between two solutions by electrical modulation of the polymer between its conducting and non-conducting states. The cation exchange membranes consisted of platinum sputter-coated polyvinylidene difluoride (PVDF) which had been coated with polypyrrole doped with sulfonated calix[6]arene (PPy(C6S)). It was shown that applying a constant potential in the range −0.4 to +0.6 V did not result in any metal ion flux across the PVDF/Pt-PPy(C6S) membrane. However, a gradual but steady increase in metal ion concentration was detected in the receiving cell when −0.8 V was applied to the membrane. To investigate the effect of film thickness on the permeability of metal ions, transport experiments were performed with composite membranes containing 2.0, 3.3, and 5.6 μm thick PPy(C6S) films. The permeability of the metals across the membrane increased as the PPy(C6S) film thickness decreased and was found to decrease in the following order: Ca 2+ > K + > Mn 2+ ≫ Co 2+, when the receiving cell contained deionised water. The PVDF/Pt-PPy(C6S) composite membrane showed significant permeability towards metal ions such as Ca 2+, K + and Mn 2+, with the flux for Ca 2+ higher than that seen for this metal ion with any previously studied PPy films containing other complexing dopants.

Sorption of toxic metals on sodium aluminosilicate (NAS)

The present study describes sorption of toxic metal ions viz: Hg 2+, Pb 2+, Cd 2+, Zn 2+ and As 3+ onto synthesized sodium aluminosilicate. A series of experiments were carried out in different conditions. Time of equilibration was observed for 5 h through kinetic study. Sorption was found to be pH dependent. In the case of Hg 2+, sorption was observed to be decreased by increasing the pH whereas it gradually increased with pH with respect to other metal ions. Sorption was observed to be decreased with the increase in metal ion concentration (10 − 2 M to 10 − 5 M) and the data was fitted well in Freundlich's isotherm. A thermodynamic study showed spontaneity of the sorption. Positive values of enthalpy and entropy indicate endothermic and increase in order of randomness at the solid–solution interface during sorption. A desorption study showed that distilled water has no capability of leaching metal ions in contrast with organic ones. The MINTEQA-2 software has been used for the aqueous speciation of the metal ions. Speciation data showed the presence of different species at different pH.

Effects of Varying the Preparation Conditions on the Dielectric Constant of Mixed Metal Oxide Films Derived from Layered Double Hydroxide Precursor Films

Magnesium/aluminum layered double hydroxide (LDH) films have been prepared in situ by means of urea hydrolysis using aluminum metal as both the substrate and sole source of aluminum. Scanning electron microscopy (SEM) images showed that the LDH crystallites are almost perpendicular to the substrate and interlaced with each other forming a network of vacant pockets. The film showed outstanding mechanical strength and high adhesion with the substrate. After being calcined at 500 °C, MgAl mixed metal oxide (MMO) films were obtained which retained the morphology of the precursor films. The values of dielectric constant (k) of the MgAl-MMO films were measured and showed low values in the range 2.0−4.7 arising from the low density of the interlaced structure. The effect of varying the preparation conditions of the LDH precursor films on the microstructure and k-value of the corresponding MMO films was investigated by varying the metal ion concentration, crystallization time, and crystallization temperature. The MMO films became more compact with increasing metal ion concentration and crystallization time, which resulted in increased k-values.

The use of free and immobilized Cunninghamella elegans for removing cobalt ions from aqueous waste solutions

This paper discusses the possible application to use free and immobilized Cunninghamella elegans for the removal of cobalt from aqueous waste solutions. Results indicated that the maximum uptake occurred at; pH 4.0–5.5 ± 0.2, temperature range between 15 and 50°C and stirring rate 250 rpm. The uptake increased with the increase of metal ion concentration up to 40 ppm. Also, it was found that the best biomass weights used for biosorption were 0.25 and 0.5 g for both free and immobilized biomass. The reuse of control alginate beads, alive and dead immobilized Cunninghamella elegans beads was investigated for five cycles. Results showed that the percent uptake decreased slightly after the first cycle. While, in the case of alginate beads there was increase in the second cycle then returned to the same level of uptake. The uptake of cobalt in the presence of Cr(VI) and Cd(II) at different mixture concentrations 40, 50 and 60 ppm was investigated. The results showed that the uptake amount of Co(II) in the presence of other metal ions was lower than Co(II) alone except for Ca-alginate beads. SEM studies for control alginate beads, alive and dead immobilized Cunninghamella elegans beads were conducted to investigate the beads before and after the accumulation of cobalt ions.

The Effects of Mn2+, Ni2+, Cu2+, Co2+ and Zn2+ Ions on Pesticide Adsorption and Mobility in a Tropical Soil

The adsorption behaviour of DDT in a tropical silt-clay soil from Kenya showed that addition of increasing metal ion concentrations from 10 to 100 microg/g of soil, reduced the % DDT adsorption in the soil by factors ranging from 6.1% to 15.4% depending on the type of metal ion. The inhibition of adsorption by metal ions was most observed in the lower ranges of metal ion concentrations in soil, i.e. up to 100 microg/g, beyond which additional increase in metal ion concentration did not result in any further increase in % adsorption. In the standard adsorption test procedure with different soil samples saturated with 100 microg/g of metal ions, the rate of adsorption of the pesticide varied with the type of metal ion and the equilibrium maximum adsorption of DDT was lowered with addition of metal ions, with the % adsorption of 78.4% (control) being reduced to lower values in the range of 67%-77.4%, depending on the type of metal ion. The data for control and samples fitted well into the Freundlich adsorption model and showed that addition of metal ions lowered the K(f) values compared with control. The results suggested that in the natural soil-water environments where there was no disturbance, aggregation of humic substances-pesticide molecule complexes altered the observed lowering of adsorption caused by inhibition by metal ions, and enhanced binding to solid soil phase occurred instead. In the leaching experiments, DDT was found to leach more extensively in soils with lower %OC content and the extent of leaching in soil columns saturated with metal ions at 100 microg/g was found to be inhibited compared with control and depended on the type of metal ion.