Highly siliceous MCM-48 from rice husk ash for CO2 adsorption

Mesoporous MCM-48 silica was synthesized using a cationic-neutral surfactant mixture as the structure-directing template and rice husk ash (RHA) as the silica source. The MCM-48 samples were characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), N₂ physisorption and SEM. X-ray diffraction pattern of the resulting MCM-48 revealed typical pattern of cubic Ia3d mesophase. BET results showed the MCM-48 to have a surface area of 1024 m²/g and FT-IR revealed a silanol functional group at about 3460 cm⁻¹. Breakthrough experiments in the presence of MCM-48 were also carried out to test the material's CO₂ adsorption capacity. The breakthrough time for CO₂ was found to decrease as the temperature increased from 298 K to 348 K. The steep slopes observed shows the CO₂ adsorption occurred very quickly, with only a minimal mass transfer effect and very fast kinetics. In addition, amine grafted MCM-48, APTS-MCM-48 (RHA), was prepared with the 3-aminopropyltriethoxysilane (APTS) to investigate the effect of amine functional group in CO₂ separation. An order of magnitude higher CO₂ adsorption capacity was obtained in the presence of APTS-MCM-48 (RHA) compared to that with MCM-48 (RHA). These results suggest that MCM-48 synthesized from rice husk ash could be usefully applied for CO₂ removal.     

Adsorption of 2,4-dichlorophenoxyacetic acid by an Andosol

To identify the important soil components involved in 2,4-dichlorophenoxyacetic acid (2,4-D) adsorption on Andosols, 2,4-D adsorption on a surface horizon of an Andosol was compared with that on hydrogen peroxide (H2O2)-treated (soil organic matter [SOM] was removed), acid-oxalate (OX)-treated (active metal hydroxides and SOM were removed), and dithionite-citrate-bicarbonate (DCB)-treated (free and active metal [hydr]oxides and SOM were removed) soil samples at equilibrium pHs ranging from 4 to 8. Although the untreated soil contained a large amount of organic C (71.9 g kg-1), removal of SOM had little effect on 2,4-D adsorption. Active surface hydroxyls, which were attached to the active and free metal (hydr)oxides and metal SOM complexes, were identified as the most important soil functional group for 2,4-D adsorption. The dominant mechanism of the 2,4-D adsorption was a ligand exchange reaction in which the carboxylic group of 2,4-D displaced the active surface hydroxyl associated with metals and formed a strong coordination bond between the 2,4-D molecule and soil solid phase. The ligand exchange reaction reasonably accounted for the selective adsorption of 2,4-D over Cl-, competitive adsorption of phosphate over 2,4-D, reduction in plant-growth-inhibitory activity of soil-adsorbed 2,4-D, and the high 2,4-D adsorption ability of Andosols. Although a humic acid purified from the soil did not adsorb 2,4-D, the presence of the humic acid increased 2,4-D adsorption on Al and Fe, probably by inhibiting the hydrolysis and polymerization of Al and Fe resulting in the preservation of available adsorption sites on these metals. The adsorption behavior of 2,4-D on soils could be a good index for predicting the adsorption behavior of other organic acids in soils.     

Some properties of a granular activated carbon-sequencing batch reactor (GAC-SBR) system for treatment of textile wastewater containing direct dyes

Resting (living) bio-sludge from a domestic wastewater treatment plant was used as an adsorbent of both direct dyes and organic matter in a sequencing batch reactor (SBR) system. The dye adsorption capacity of the bio-sludge was not increased by acclimatization with direct dyes. The adsorption of Direct Red 23 and Direct Blue 201 onto the bio-sludge was almost the same. The resting bio-sludge showed higher adsorption capacity than the autoclaved bio-sludge. The resting bio-sludge that was acclimatized with synthetic textile wastewater (STWW) without direct dyes showed the highest Direct Blue 201, COD, and BOD(5) removal capacities of 16.1+/-0.4, 453+/-7, and 293+/-9 mg/g of bio-sludge, respectively. After reuse, the dye adsorption ability of deteriorated bio-sludge was recovered by washing with 0.1% sodium dodecyl sulfate (SDS) solution. The direct dyes in the STWW were also easily removed by a GAC-SBR system. The dye removal efficiencies were higher than 80%, even when the system was operated under a high organic loading of 0.36kgBOD(5)/m(3)-d. The GAC-SBR system, however, showed a low direct dye removal efficiency of only 57+/-2.1% with raw textile wastewater (TWW) even though the system was operated with an organic loading of only 0.083kgBOD(5)/m(3)-d. The dyes, COD, BOD(5), and total kjeldalh nitrogen removal efficiencies increased up to 76.0+/-2.8%, 86.2+/-0.5%, 84.2+/-0.7%, and 68.2+/-2.1%, respectively, when 0.89 g/L glucose (organic loading of 0.17kgBOD(5)/m(3)-d) was supplemented into the TWW.     

吸附-双催化氧化降解苯胺、硝基苯废水

苯胺、硝基苯废水利用吸附树脂吸附后,再利用过氧化氢作氧化剂,在亚铁离子和紫外光的双催化下氧化降解。通过对亚铁离子浓度、过氧化氢浓度等因素对光降解影响的考察,结果表明,在实验条件下,本氧化体系对苯胺、硝基苯废水有明显的降解效果,苯胺、硝基苯废水经该体系处理12h后,去除率最高分别达到99.7%和95.3%。     

The influence of lipids on the energetics of uptake of polycyclic aromatic hydrocarbons by natural organic matter

Although most of the organic carbon in soils and sediments may be composed of humic substances, their interaction with other compounds, especially their sorption interactions, may be significantly affected by the presence of small amounts of the other components of natural organic matter (NOM). In this investigation, the influence of the lipid fraction of NOM on the sorption thermodynamics of fluorene, phenanthrene, and pyrene to several geosorbent samples was examined before and after extraction of lipids. Batch experiments were performed at the same concentration for all polycyclic aromatic hydrocarbons (PAHs) (0.025 x their solubility in water) at different temperatures (10, 20, 30, and 40 degrees C), and the thermodynamic parameters were calculated. Removal of the lipids increases the sorption capacity of the samples as well as the exothermicity of the process. The free energy change was negative for all the samples and no significant differences were noticed on lipid removal. The entropy changes were small and positive for the whole geosorbent samples, but even smaller or more negative when the lipids were removed. This indicates that the interaction of PAHs with soils and sediments in the absence of extractable lipids is stronger and the mechanisms involved may be different, changing from a partitioning-like mechanism to specific adsorption. Because of the competition between lipids and PAHs for the same sorption sites, the lipids can be viewed as an "implicit sorbate."     

叉鞭金藻净化废水中微量铅的研究

以叉鞭金藻作为生物吸附剂，去除废水中微量Pb^2 。结果表明，培养4d左右的叉鞭金藻对Pb^2 的去除能力最强；随着藻细胞密度的增大，藻体对Pb^2 的去除率也增大；当pH为5～7时，藻细胞对Pb^2 有较好的吸附作用。研究还表明，叉鞭金藻对Pb^2 的生物吸附经历了快速的吸附和缓慢的吸收两个步骤；离子强度Pb^2 的吸附有一定的抑制作用；在一定的浓度范围内，叉鞭金藻对Pb^2 的生物吸附符合Freundlich等温吸附模型。     

Kinetic and equilibrium characterization of uranium(VI) adsorption onto carboxylate-functionalized poly(hydroxyethylmethacrylate)-grafted lignocellulosics

This study investigated the feasibility of using a new adsorbent prepared from coconut coir pith, CP (a coir industry-based lignocellulosic residue), for the removal of uranium [U(VI)] from aqueous solutions. The adsorbent (PGCP-COOH) having a carboxylate functional group at the chain end was synthesized by grafting poly(hydroxyethylmethacrylate) onto CP using potassium peroxydisulphate-sodium thiosulphite as a redox initiator and in the presence of N,N'-methylenebisacrylamide as a crosslinking agent. IR spectroscopy results confirm the graft copolymer formation and carboxylate functionalization. XRD studies confirm the decrease of crystallinity in PGCP-COOH compared to CP, and it favors the protrusion of the functional group into the aqueous medium. The thermal stability of the samples was studied using thermogravimetry (TG). Surface charge density of the samples as a function of pH was determined using potentiometric titration. The ability of PGCP-COOH to remove U(VI) from aqueous solutions was assessed using a batch adsorption technique. The maximum adsorption capacity was observed at the pH range 4.0-6.0. Maximum removal of 99.2% was observed for an initial concentration of 25mg/L at pH 6.0 and an adsorbent dose of 2g/L. Equilibrium was achieved in approximately 3h. The experimental kinetic data were analyzed using a first-order kinetic model. The temperature dependence indicates an endothermic process. U(VI) adsorption was found to decrease with an increase in ionic strength due to the formation of outer-sphere surface complexes on PGCP-COOH. Equilibrium data were best modeled by the Langmuir isotherm. The thermodynamic parameters such as DeltaG(0), DeltaH(0) and DeltaS(0) were derived to predict the nature of adsorption. Adsorption experiments were also conducted using a commercial cation exchanger, Ceralite IRC-50, with carboxylate functionality for comparison. Utility of the adsorbent was tested by removing U(VI) from simulated nuclear industry wastewater. Adsorbed U(VI) ions were desorbed effectively (about 96.2+/-3.3%) by 0.1M HCl. The adsorbent was suitable for repeated use (more than four cycles) without any noticeable loss of capacity.     

Utilization of powdered waste sludge (PWS) for removal of textile dyestuffs from wastewater by adsorption

Acid pre-treated powdered waste sludge (PWS) was used for removal of textile dyestuffs from aqueous medium by adsorption as an alternative to the use of powdered activated carbon (PAC). The rate and extent of dysetuff removals were determined for four different dyestuffs at different PWS concentrations varying between 1 and 6 gl(-1). Biosorbed dyestuff concentrations at equilibrium decreased with increasing PWS concentration for all dyestuffs tested. PWS was more effective for adsorption of Remazol red RR and Chrisofonia direct yellow 12 as compared to the other dyestuffs tested. More than 80% percent dyestuff removal was obtained for all dyestuffs at PWS concentrations above 4 gl(-1) after 6h of incubation. Similar to percent dyestuff removal, the rate of adsorption was maximum at a PWS concentration of 4 gl(-1). Kinetics of adsorption of dyestuffs was investigated by using the first- and second-order kinetic models and the kinetic constants were determined. Second-order kinetics was found to fit the experimental data better than the first-order model for all dyestuffs tested. Adsorption isotherms were established for all dyestuffs used and the isotherm constants were determined by using the experimental data. Langmuir and the generalized adsorption isotherms were found to be more suitable than the Freundlich isotherm for correlation of equilibrium adsorption data. Acid pre-treated PWS was proven to be an effective adsorbent for dyestuff removal as compared to the other adsorbents reported in literature studies.     

石油化工企业含苯胺消防污水处理技术研究

针对石油化工企业含苯胺的消防污水,利用基于过氧化氢和氯化铁为氧化剂的深度氧化技术,通过氧化、絮凝、过滤和吸附对消防污水进行处理。实验确定氧化剂的投加量为理论投加量,氧化时间1.0h,消防污水pH值为6.86时,絮凝剂最佳使用浓度约为2%,消防污水中苯胺和COD去除率达到99.5%以上,达到了消防污水处理效果。     

Trapping phosphorus in runoff with a phosphorus removal structure

Reduction of phosphorus (P) inputs to surface waters may decrease eutrophication. Some researchers have proposed filtering dissolved P in runoff with P-sorptive byproducts in structures placed in hydrologically active areas with high soil P concentrations. The objectives of this study were to construct and monitor a P removal structure in a suburban watershed and test the ability of empirically developed flow-through equations to predict structure performance. Steel slag was used as the P sorption material in the P removal structure. Water samples were collected before and after the structure using automatic samples and analyzed for total dissolved P. During the first 5 mo of structure operation, 25% of all dissolved P was removed from rainfall and irrigation events. Phosphorus was removed more efficiently during low flow rate irrigation events with a high retention time than during high flow rate rainfall events with a low retention time. The six largest flow events occurred during storm flow and accounted for 75% of the P entering the structure and 54% of the P removed by the structure. Flow-through equations developed for predicting structure performance produced reasonable estimates of structure "lifetime" (16.8 mo). However, the equations overpredicted cumulative P removal. This was likely due to differences in pH, total Ca and Fe, and alkalinity between the slag used in the structure and the slag used for model development. This suggests the need for an overall model that can predict structure performance based on individual material properties.     

Attenuation of divalent toxic metal ions using natural sericitic pyrophyllite

The present study investigated the effectiveness of an inexpensive and ecofriendly alumino silicate clay mineral, sericitic pyrophyllite, as an adsorbent for the possible application in the removal of some divalent toxic metal cations such as Pb(2+), Cu(2+)and Zn(2+) from aqueous systems. Batch scale equilibrium adsorption studies were carried out for a wide range of initial concentration from 24.1 to 2410mumolL(-1) for lead, 78.65 to 7865mumolL(-1) for copper and 76.45 to 7645mumolL(-1) for zinc solutions. The removal of Pb(2+) was almost complete at low concentration (maximum lead removal capacity, LRC, 32mg of lead/g of pyrophyllite) with 10gL(-1) of adsorbent in a 30min equilibration time. The effects of temperature on adsorption of heavy metal ions were studied. The applicability of the Langmuir, Freundlich and Dubinin-Radushkevich adsorption models in each case of lead, copper and zinc adsorption was examined separately at different temperatures. The adsorption process was found to be endothermic and the Freundlich adsorption model was found to represent the data at different temperatures more suitably.     

Removal of selenate from water by zerovalent iron

Zerovalent iron (ZVI) has been widely used in the removal of environmental contaminants from water. In this study, ZVI was used to remove selenate [Se(VI)] at a level of 1000 microg L(-1) in the presence of varying concentrations of Cl-, SO(2-)4, NO(-)3, HCO(-)3, and PO(3-)4. Results showed that Se(VI) was rapidly removed during the corrosion of ZVI to iron oxyhydroxides (Fe(OH)). During the 16 h of the experiments, 100 and 56% of the added Se(VI) was removed in 10 mM Cl- and SO(2-)4 solutions under a closed contained system, respectively. Under an open condition, 100 and 93% of the added Se(VI) were removed in the Cl- and SO(2-)4 solutions, respectively. Analysis of Se species in ZVI-Fe(OH) revealed that selenite [Se(IV)] and nonextractable Se increased during the first 2 to 4 h of reaction, with a decrease of Se(VI) in the Cl- experiment and no detection of Se(VI) in the SO(2-)4 experiment. Two mechanisms can be attributed to the rapid removal of Se(VI) from the solutions. One is the reduction of Se(VI) to Se(IV), followed by rapid adsorption of Se(IV) to Fe(OH). The other is the adsorption of Se(VI) directly to Fe(OH), followed by its reduction to Se(IV). The results also show that there was little effect on Se(VI) removal in the presence of Cl- (5, 50, and 100 mM), NO(-)3 (1, 5, and 10 mM), SO(2-)4 (5 mM), HCO(-)3 (1 and 5 mM), or PO(3-)4 (1 mM) and only a slight effect in the presence of SO(2-)4 (50 and 100 mM), HCO(-)3 (10 mM), and PO(3-)4 (5 mM) during a 2-d experiment, whereas 10 mM PO(3-)4 significantly inhibited Se(VI) removal. This work suggests that ZVI may be an effective agent to remove Se from Se-contaminated agricultural drainage water.     

Adsorption of cadmium on biosolids-amended soils

Debate exists over the biosolid phase (organic or inorganic) responsible for the reduction in phytoavailable Cd in soils amended with biosolids as compared with soils amended with inorganic salts. To test the importance of these two phases, adsorption isotherms were developed for soil samples (nine biosolids-amended soils and their five companion controls) and two biosolids samples from five experimental sites with documented histories of biosolids application. Subsamples were treated with 0.7 M NaClO to remove organic carbon. Cadmium nitrate was added to both moist soil samples and their soil inorganic fractions (SIF) in a 0.01 M Ca(NO3)2 solution at three pH levels (6.5, 5.5, and 4.5), and equilibrated at 22 +/- 1 degrees C for at least 48 h. Isotherms of Cd adsorption for biosolids-amended soil were intermediate to the control soil and biosolids. Decreasing pH did not remove the difference between these isotherms, although adsorption of Cd decreased with decreasing pH level. Organic matter removal reduced Cd adsorption on all soils but had little influence on the observed difference between biosolids-amended and control soils. Thus, increased adsorption associated with biosolids application was not limited to the organic matter addition from biosolids; rather, the biosolids application also altered the adsorptive properties of the SIF. The greater affinity of the inorganic fraction of biosolids-amended soils to adsorb Cd suggests that the increased retention of Cd on biosolids-amended soils is independent of the added organic matter and of a persistent nature.     

Application of 'waste' wood-shaving bottom ash for adsorption of azo reactive dye

The utilization of wood-shaving bottom ash (WBA) for the removal of Red Reactive 141 (RR141), an azo reactive dye, was investigated. WBA/H(2)O and WBA/H(2)SO(4) were made by treating WBA with water and 0.1M H(2)SO(4), respectively, to increase adsorption capacity. Adsorption of RR141 from reactive dye solution (RDS) and reactive dye wastewater (RDW) by WBA/H(2)O and WBA/H(2)SO(4) involved the BET surface area and pore size diameter. Properties of adsorbents, effect of contact time, initial pH of solution, dissolved metals and elution studies indicated that the decolorisation mechanism involved both chemical adsorption and precipitation with calcium ions. In addition, the WBA/H(2)SO(4) surface might contain sulphate-cation complexes that were specific to enhancing dye adsorption from RDW. The adsorption isotherm had a best fit by the Freundlich model. Freundlich parameters showed that WBA/H(2)O used more heterogeneous surface than WBA/H(2)SO(4) and activated carbon for RDW adsorption. A thermodynamic study indicated that RDW adsorption was an endothermic process. The maximum dye adsorption capacities of WBA/H(2)O, WBA/H(2)SO(4) and activated carbon obtained from a Langmuir model at 30 degrees C were 24.3, 29.9, and 41.5mgl(-1), respectively. In addition, WBA/H(2)O and WBA/H(2)SO(4) could reduce colour and high chemical oxygen demand (COD) of real textile wastewater. According to the difficulty in the elution study, it was an environmentally safe disposal of this waste. Therefore, WBA, a waste from combustion of wood shavings, was suitable to be used as an effective adsorbent for azo reactive dye removal.     

Removal of heavy metals in rinsing wastewater from plating factory by adsorption with economical viable materials

The removal of heavy metals from plating factory wastewater with economical materials was investigated by the column method. Montmorillonite, kaolin, tobermorite, magnetite, silica gel and alumina were used as the economical adsorbents to wastewater containing Cd(II), Cr(VI), Cu(II) and Pb(II). This removal method of heavy metals proved highly effective as removal efficiency tended to increase with increasing pH and decrease with increasing metal concentration. The removal percentages by adsorption onto montmorillonite, tobermorite, magnetite, and silica gel showed high values for all metals. From the results for the heat of adsorption, the adsorption process in the present study might be chemisorption. The proposed method was successfully applied to the removal of Cd(II), Cr(VI) and Cu(II) in rinsing wastewater from plating factory in Nagoya City, Aichi Prefecture, Japan. Since the economical adsorbents used can be obtained commercially because they are easily synthesized, the wastewater treatment system developed is rapid, simple and cheap for the removal of heavy metals.     

WATER RECLAMATION BY PHYSICOCHEMICAL TREATMENT OF WASTEWATER1

ABSTRACT. Treatment of a high strength acidic industrial chemical waste, which had a COD of about 3000 mg/1 and a pH of 3, was attempted by activated carbon adsorption to evaluate the feasibility of yielding effluents of reusable qualities. The experimental methods which were employed in this investigation included batch and column studies. The former was used to evaluate the rate and equilibrium of carbon adsorption while the latter was used to determine treatment efficiencies and performance characteristics. Parallel operations of fixed-bed and expanded-bed adsorbers were contrasted in the column study. Results of this investication indicate that activated carbon was very efficient in removing the COD of the chemical waste. Initial pH adjustments for the wastewater to 7.0 or 11.4 did not increase the COD removal efficiency. Turbidity and nitrogen (total Kjeldahl- and ammonia-N) were removed to some extents by the carbon bed adsorbers while phosphorus (total-and ortho-P) was totally unaffected by the carbon treatment.     

Phenol removal from aqueous environments by natural & chemically modified kaolin clay

Natural, acid and base modified kaolin clays were studied for the sake of phenol and 4-chlorophenol removal from aqueous environments and their application to real ground and industrial wastewater samples. Scanning electron microscope (SEM), infrared spectroscopy (IR), X-ray diffraction (XRD), Thermo Gravimetric Analysis (TGA), Differential Thermal Analysis (DTA), and Surface area analysis were employed for characterization of the adsorbents microstructure. Operating factors such as adsorbent dose, solution pH, initial phenol concentration, and contact time were studied. The experimental data displayed that the increase of the adsorbent dose, contact time, and pH value from 2 to 7 increases the efficiency of the removal process. Optimal conditions for phenolic removal were; contact time of 300 min, primary phenol solution of 25 mg/L, pH 7 and 2.5 g/L as an appropriate adsorbent dose using crude (natural), acid modified and base modified kaolin clays. The higher phenolic removal efficiencies were obtained at 5 mg/L as 90, 97, 96.2%, respectively, for the adsorbents in the previously mentioned order. The adsorption capacity in the removal of phenol and 4-chlorophenol were 7.481 and 4.195, 8.2942 and 3.211, and 8.05185 and 18.565 mg/g, respectively, for the adsorbents in the same mentioned order. The adsorption equilibrium data were fitted and analyzed with four isotherm models, namely, Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich isotherm equations. The adsorption process of phenol on studied adsorbents was exothermic, spontaneous and thermodynamically favorable proved by the negative values of their thermodynamic parameters ΔH° and ΔG°. The correlation coefficient (R²) for all concentrations was higher than 0.94, which indicates that in the studied system, the data suitably fit the first-order kinetics. The % desorption capacity was amounted to 96%, 91.11%, and 87.06% of adsorbed phenol, respectively, for the adsorbents in the previous order using 0.1N NaOH and 10% V/V ethanol solutions as eluents at 25°C, indicating the reusability of the adsorbents. Kaolin and its modified forms can be introduced as eco-friendly and low-cost adsorbents in water remediation implementation.     

Removal of Fe(II) from the wastewater of a galvanized pipe manufacturing industry by adsorption onto bentonite clay

Bentonite clay has been used for the adsorption of Fe(II) from aqueous solutions over a concentration range of 80-200 mg/l, shaking time of 1-60 min, adsorbent dosage from 0.02 to 2 g and pH of 3. The process of uptake follows both the Langmuir and Freundlich isotherm models and also the first-order kinetics. The maximum removal (>98%) was observed at pH of 3 with initial concentration of 100 mg/l and 0.5 g of bentonite. The efficiency of Fe(II) removal was also tested using wastewater from a galvanized pipe manufacturing industry. More than 90% of Fe(II) can be effectively removed from the wastewater by using 2.0 g of the bentonite. The effect of cations (i.e. zinc, manganese, lead, cadmium, nickel, cobalt, chromium and copper) on the removal of Fe(II) was studied in the concentration range of 10-500 mg/l. All the added cations reduced the adsorption of Fe(II) at high concentrations except Zn. Column studies have also been carried out using a certain concentration of wastewater. More than 99% recovery has been achieved by using 5 g of the bentonite with 3M nitric acid solution.     

Quaternized agricultural by-products as anion exchange resins

The objectives of this study were the chemical modification of readily available, low-cost agricultural by-products to anion exchange resins and the selection of the best modified by-product for further use in anion removal. Resins were prepared through the quaternization of a series of 12 agricultural by-products with N-(3-chloro-2-hydroxypropyl) trimethylammonium chloride (CHMAC). Phosphate ion adsorption assays were conducted at pH 7 in order to compare adsorption properties among the by-products. Quaternized corn stover showed the highest phosphorus adsorption at 0.66 mmole/g. Since corn stover exhibited the best uptake of phosphate ion, it was compared to a commercially available, cellulose-based anion exchange resin. Additionally, adsorption capacities of quaternized corn stover for arsenate, chromate, and selenate were evaluated and adsorption efficiencies were determined in simulated wastewater samples. Our results indicate that modified corn stover demonstrates good adsorption uptake for arsenate and selenate and especially for chromate.     

Efficiency of removal of cadmium from aqueous solutions by plant leaves and the effects of interaction of combinations of leaves on their removal efficiency

Removal of cadmium from aqueous solutions using 20 species of plant leaves and combinations of these leaves have been studied. Several factors affecting the removal efficiency have been studied. The most efficient types of plant leaves for the removal of cadmium are those of styrax, plum, pomegranate and walnut. The interaction effect of the combined leaf samples on the efficiency of removal of cadmium has been found to be additive in combinations involving styrax plant leaves but seems to be antagonistic in all other combinations. The optimum experimental conditions for removal of cadmium have been found to be at pH 4.1, using high concentrations of naturally dried plant leaves, using ground leaves and to remove cadmium from agitated aqueous solutions. The percentage of metal removed at an initial cadmium concentration of 10mg/l by the most efficient types of leaves have been found to be 85% for styrax leaves, 85% for plum leaves, 80% for pomegranate leaves, 78% for walnut leaves and 77% for meddler leaves. The presence of foreign ions or complexing agents has been found to reduce the efficiency of removal of cadmium by plant leaves. About 80-85% of the cadmium in charged plant leaves has been released under the influence of changing the pH of the solution, addition of competing ions and the addition of EDTA. The results of removal of cadmium by plant leaves have been found to follow the Freundlich adsorption isotherm, first-order reaction with respect to cadmium and to have intra-pore diffusion as the rate-limiting step.