Removal of metal ions using lignite in aqueous solution—Low cost biosorbents

Turkish lignite can be used as a new adsorption material for removing some toxic metals from aqueous solution. The adsorption of lignite (brown young coals) to remove copper (Cu²⁺), lead (Pb²⁺), and nickel (Ni²⁺) from aqueous solutions was studied as a function of pH, contact time, metal concentration and temperature. Adsorption equilibrium was achieved between 40 and 70 min for all studied cations except Pb²⁺, which is between 10 and 30 min. The adsorption capacities are 17.8 mg/g for Cu²⁺, 56.7 mg/g for Pb²⁺, 13.0 mg/g for Ni²⁺ for BC₁ (Ilg?n lignite) and 18.9 mg/g for Cu²⁺, 68.5 mg/g for Pb²⁺, 12.0 mg/g for Ni²⁺ for BC₂ (Beysehir lignite) and 7.2 mg/g for Cu²⁺, 62.3 mg/g for Pb²⁺, 5.4 mg/g for Ni²⁺ for AC (activated carbon). More than 67% of studied cations were removed by BC₁ and 60% BC₂, respectively from aqueous solution in single step. Whereas about 30% of studied cations except Pb²⁺, which is 90%, were removed by activated carbon. Effective removal of metal ions was demonstrated at pH values of 3.8–5.5. The adsorption isotherms were measured at 20 °C, using adsorptive solutions at the optimum pH value to determine the adsorption capacity. The Langmuir adsorption isotherm was used to describe observed sorption phenomena. The rise in temperature caused a slight decrease in the value of the equilibrium constant (K_c) for the sorption of metal ions. The mechanism for cations removal by the lignite includes ion exchange, complexation and sorption. The process is very efficient especially in the case of low concentrations of pollutants in aqueous solution, where common methods are either economically unfavorable or technically complicated.     

Simultaneous adsorption of phenol and Cu2+ from aqueous solution by activated carbon/chitosan composite

A multifunction adsorbent was synthesized by incorporating AC into CTS, and the ratio of AC to CTS was 1/1. The resultant was called activated carbon (AC)/chitosan (CTS) composite. The simultaneous adsorption of phenol and Cu²⁺ from aqueous solution onto AC/CTS composite was investigated by a batch procedure. The adsorption processes for both Cu²⁺ and phenol obeyed the pseudo second-order kinetic model. Phenol was prone to be adsorbed more quickly as compared with Cu²⁺ when they coexisted in solution. The adsorption behavior of both phenol and Cu²⁺ followed the Langmuir isotherm. The maximum adsorption capacities of phenol and Cu²⁺ were 34.19 mg/g and 74.35 mg/g at 293 K, respectively. No obvious competitive adsorption existed between phenol and Cu²⁺.     

Preparation of graphene oxide/carboxymethyl chitosan/polyvinyl alcohol composite nanofiber membranes by electrospinning for heavy metal adsorption

In this paper, a graphene-oxide/carboxymethyl-chitosan/polyvinyl-alcohol (GO/CMC/PVA) composite nanofiber membrane was prepared by electrospinning and cross-linking with glutaraldehyde (GA) to improve the water resistance. The composite nanofiber membrane can be used in the field of heavy metal adsorption. The membrane was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. The effects of GO concentration, adsorption time, and initial concentration of heavy-metal ion (Ni²⁺, Cu²⁺, Ag⁺, and Pb²⁺) solution on the adsorption performance of the fiber membranes were investigated. The results showed that the addition of GO can reduce the diameter of nanofibers. GO, CMC, and PVA exhibited good compatibility, and the intermolecular hydrogen bonding improved. The addition of GO also improved the crystalline properties of the composite fiber membrane. In the optimal cross-linking condition, GA was saturated by steam cross-linking for 6 h. The introduction of GO improved the adsorption capacity of the membrane for heavy metals in water. The utmost adsorption capacities for Ni²⁺, Cu²⁺, Ag⁺, and Pb²⁺ were 262.1, 237.9, 319.3, and 413.6 mg/g when using the cross-linked composite fiber membranes, respectively. The results of adsorption kinetics and thermodynamics showed that the adsorption process accorded with the pseudo-second-order kinetic model and Langmuir–Freundlich isotherm model.     

Biomass grafted with polyamic acid for enhancement of cadmium(II) and lead(II) biosorption

In this study, a simple method was used to prepare modified biomass to improve its adsorption capacity for Cd²⁺ and Pb²⁺. The modified biomass of baker’s yeast was obtained by grafting polyamic acid, which was prepared via the reaction of pyromellitic dianhydride (PMDA) and lysine, onto the surface of glutaraldehyde-pretreated biomass at 50 °C for 3 h. The presence of polyamic acid on the biomass surface was verified by Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS), the morphologies of the biomass before and after modification were observed by microscope. Due to the high density of the carboxyl and amide groups on the biomass surface, the uptake for Cd²⁺ and Pb²⁺ showed a significant increase. According to Langmuir adsorption isotherm, the maximum uptake for Cd²⁺ and Pb²⁺ were 95.2 and 204.5 mg g⁻¹, which were 15- and 11-fold for that obtained on the uncontaminated biomass. The kinetics for Cd²⁺ and Pb²⁺ adsorption followed the pseudo-second-order model. The results of FTIR and XPS revealed that carboxyl, amide, and hydroxyl groups on the biomass surface were involved in the adsorption of Cd²⁺ and Pb²⁺.     

The heavy metal adsorption characteristics on metakaolin-based geopolymer

Since porous materials often function as adsorbents, this study chose to investigate the adsorption of heavy metals by geopolymers. The geopolymer was made by condensing a mixture of metakaolin and alkali solution at a fixed ratio at room temperature and then pre-crashed to a fixed-radius size. This paper examined the adsorption efficiency of the geopolymer for different heavy metals (i.e., Pb²⁺, Cu²⁺, Cr³⁺, and Cd²⁺) in aqueous solutions under discrete experimental parameters. The experimental results verified that the geopolymer could adsorb heavy metals. Of the metals tested, optimal adsorption with the implementation of the geopolymer occurred with Pb²⁺. The data fit both the pseudo-second-order and the Langmuir equations. This discovery may facilitate the development of optimized procedures for wastewater treatment, thus providing an alternative solution to environmental damages caused by heavy metal pollutants.     

Adsorption properties of Pb2+ on thermal-activated serpentine

ABSTRACT

Adsorption properties of nature and thermal-activated serpentines to Pb²⁺ in aqueous solution were investigated. The results showed that Freundlich isotherm and pseudo-second-order kinetics model were suitable to describe the adsorption process of Pb²⁺ on serpentines. The thermodynamic parameters indicated that the adsorption process was endothermic and spontaneous. The serpentine activated at 700°C exhibited maximum adsorption capacity to Pb²⁺. Based on the XRD and XPS characterization, it could be found that the structure of serpentine did not change significantly during the adsorption process, and Pb²⁺ was adsorbed on the serpentine surface as the precipitation of Pb(OH)Cl and Pb(OH)₂.     

Synthesis of magnetic Fe3O4@SiO2-(-NH2/-COOH) nanoparticles and their application for the removal of heavy metals from wastewater

In this work, Fe₃O₄@SiO₂-(-NH₂/-COOH) nanoparticles were synthesized for the removal of Cd²⁺, Pb²⁺ and Zn²⁺ ions from wastewater. The results of characterization showed that Fe₃O₄@SiO₂-(-NH₂/-COOH) was superparamagnetic with a core–shell structure. The surface of Fe3O4 was successfully coated with silica and modified with amino groups and carboxyl groups through the use of a silane coupling agent, polyacrylamide and polyacrylic acid. The dispersion of the particles was improved, and the surface area of the Fe3O4@SiO2-(-NH2/-COOH) nanoparticles was 67.8 m²/g. The capacity of Fe₃O₄@SiO₂-(-NH₂/-COOH) to adsorb the three heavy metals was in the order Pb²⁺ > Cd²⁺ > Zn²⁺, and the optimal adsorption conditions were an adsorption dose of 0.8 g/L, a temperature of 30°C and concentrations of Pb²⁺, Cd²⁺ and Zn²⁺ below 120, 80 and 20 mg/L, respectively. The maximum adsorption capacities for Pb²⁺, Cd²⁺ and Zn²⁺ were 166.67, 84.03 and 80.43 mg/g. The adsorption kinetics followed a pseudo-second-order model and Langmuir isotherm model adequately depicted the isotherm adsorption process. Thermodynamic analysis showed that the adsorption of the three metal ions was an endothermic process and that increasing the temperature was conducive to this adsorption.     

Preparation and adsorption mechanism of polyvinyl alcohol/graphene oxide-sodium alginate nanocomposite hydrogel with high Pb(II) adsorption capacity

A series of polyvinyl alcohol (PVA)/graphene oxide (GO)-sodium alginate (SA) nanocomposite hydrogel beads were prepared through in situ crosslinking for Pb²⁺ removal. It was found that PVA and SA molecules were intercalated into GO layers through hydrogen bonding interactions, leading to the destruction of orderly structure of GO, while GO uniformly distributed in PVA matrix. With increasing PVA solution concentration, the hydrogel beads became more regular, a large number of polygonal pores with thin walls and open pores formed, the average pore size decreased, and the dense network structure formed. Meanwhile, the permeability of the composite hydrogel decreased, leading to the decline of Pb²⁺ adsorption capacity of the composite hydrogel. With increasing GO content, the ballability of the hydrogel beads was weakened, the pore size increased, and relatively loose network structure formed, resulting in an increase in permeability and Pb²⁺ adsorption capacity of the hydrogel, reaching up to 279.43 mg g⁻¹. Moreover, the composite hydrogel presented relatively good reusability for Pb²⁺ removal. The adsorption mechanism was explored and showed that the adsorption system of the composite hydrogel belonged to the second-order kinetic model and fitted Langmuir adsorption isotherm model for Pb²⁺ removal, which might be mono-layer chemical adsorption. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47318.     

Peanut Shell Activated Carbon： Characterization,Surface Modification and Adsorption of Pb^2＋ from Aqueous Solution

Metal ion contamination of drinking water and waste water, especially with heavy metal ion such as lead, is a serious and ongoing problem. In this work, activated carbon prepared from peanut shell （PAC） was used for the removal of Pb^2＋ from aqueous solution. The impacts of the Pb25 adsorption capacities of the acid-modified carbons oxidized with HNO3 were also investigated. The surface functional groups of PAC were confirmed by Fourier transform infrared （FTIR） spectroscopy, X-ray photoelectron spectroscopy （XPS）, Boehm titration. The textural properties （surface area, total pore volume） were evaluated from the nitrogen adsorption isotherm at 77 K. The experimental results presented indicated that the adsorption data fitted better with the Langmuir adsorption model. A comparative study with a commercial granular activated carbon （GAC） showed that PAC was 10.3 times more efficient compared to GAC based on Langmuir maximum adsorption capacity. Further analysis results by the Langmuir equation showed that HNO3 [20% （by mass）] modified PAC has larger adsorption capacity of Pb^2＋ from aqueous solution （as much as 35.5 mg·g^-1）. The adsorption capacity enhancement ascribed to pore widening, increased cation-exchange capacity by oxygen groups, and the promoted hydrophilicity of the carbon surface.     

Removal of Lead(II) from Aqueous Solutions using Pre-boiled and Formaldehyde-Treated Onion Skins as a New Adsorbent

The adsorption characteristics of Pb²⁺ on pre-boiled treated onion skins (PTOS) and formaldehyde-treated onion skins (FTOS) were evaluated. The effects of Pb²⁺ initial concentration, agitation rate, solution pH, and temperature on Pb²⁺ adsorption were investigated in batch systems. Pb²⁺ adsorption was found to increase with increase in initial concentration. The point of zero net charge (PZC) was 6.53. The optimum pH for the maximum removal of Pb²⁺ was 6.0. The adsorption equilibrium data was best represented by the Langmuir isotherm model for FTOS and the Freundlich isotherm model for PTOS. The maximum amounts of Pb²⁺ adsorbed (qm), as evaluated by the Langmuir isotherm, was 200 mgg^?1 for FTOS. The efficiencies of PTOS and FTOS for Pb²⁺ removal were 84,8.0% and 93.5% at 0.15 g/200 mL^?1 adsorbent dose, respectively. (C ₀ = 50 mg L^?1). Study concluded that onion skins, a waste material, have good potential as an adsorbent to remove toxic metals like Pb²⁺ from water. Boehm titration analysis was conducted to determine the surface groups. It was found that the adsorption kinetics of Pb²⁺ obeyed pseudo-first-order kinetic model as based on Δq (%) values. FTIR and SEM images before and after adsorption was recorded to explore changes in adsorbent-surface morphology. Activation energy (Ea) was obtained as 25.596 kJ/mol.     

Synthesis and adsorption performance of fly ash/steel slag-based geopolymer for removal of Cu (II) and methylene blue

In order to realize the value-added resource utilization of solid waste, geopolymer particle adsorbents were prepared at low temperatures using silica-aluminum-rich fly ash and steel slag powders as raw materials. In order to investigate the mechanism of their adsorption of dyes and heavy metal ions from wastewater, the effects of steel slag/fly ash ratio, adsorbent dosage, initial concentration of methylene blue (MB) and Cu²⁺ solution, adsorption time and temperature on the adsorption performance of the fly ash/steel slag-based geopolymer adsorbents were investigated, systematically. Results presented that the adsorption capacities of MB and Cu²⁺ were 33.30 and 24.15 mg/g, and the removal efficiencies were 99.90% and 96.59% with the dosages of 3 and 4 g/L geopolymer adsorbents (steel slag/fly ash ratio of 20 wt.%), respectively. The adsorption processes of MB and Cu²⁺ on the adsorbents were in accordance with the proposed pseudo-second-order and Langmuir isotherm models, which mainly included physical and chemical adsorption mechanisms. The adsorption was a spontaneous endothermic process. The fly ash/steel slag-based geopolymer had good removal ability for dyes and heavy metal ions, and it could maintain good adsorption performance after three cycles of regeneration. It had potential application in wastewater treatment.     

Novel design of microsphere adsorbent for efficient heavy metals adsorption

The fabrication of high-efficiency and low-cost adsorbent for the wastewater treatment is a challenging task. In this study, a hollow sphere adsorbent was synthesized from solid waste coal gangue through a facile spray drying method and subsequent calcination. The structure of the synthesized coal gangue microsphere (CM) have been characterized by multimethods including X-ray diffraction, scanning electron microscope, Fourier transform infrared, and others. The factors influencing the adsorption for Cu²⁺ and Pb²⁺ by CM were also investigated systemically; pH between 6 and 8 was found to be optimal for Cu²⁺ and Pb²⁺ adsorption. The isotherm and kinetic analysis reveal that the adsorption process could be well represented by Langmuir and pseudo–second-order model with a higher R² and low χ² value. According to Langmuir model, the maximum adsorption capacity was calculated to be 6.570 and 18.904 mg/g for Cu²⁺ and Pb²⁺ at 25°C, respectively. The adsorption mechanism was proposed to contain not only the surface reaction process, but also the diffusion process. Consequently, the economic and environmental benefits make CM a promising adsorbent in wastewater treatment.     

Adsorption of Pb2+ and Cd2+ onto a Novel Activated Carbon‐Chitosan Complex

A novel activated carbon‐chitosan complex adsorbent (ACCA) was prepared via the crosslinking of glutaraldehyde and activated carbon‐(NH₂‐protected) chitosan complex under microwave irradiation. The surface morphology of this adsorbent was characterized. The adsorption of ACCA for Pb²⁺ and Cd²⁺ was investigated. The results demonstrate that ACCA has higher adsorption capacity than chitosan. The adsorption follows pseudo first‐order kinetics. The isotherm adsorption equilibria are better described by Freundlich and Dubinin‐Radushkevich isotherms than by the Langmuir isotherm. The adsorbent can be recycled. These results have important implications for the design of low‐cost and effective adsorbents in the removal of heavy metal ions from wastewaters.     

Morphological,transport, and adsorption properties of ethylene vinyl acetate/polyurethane/bentonite clay composites

The effect of polyurethane (PU) foam on the morphological and transport properties of ethylene vinyl acetate (EVA) with 9% vinyl acetate and the potential application of 3%bentonite/28.5% PU/68.5% EVA composites fabricated via the melt‐blending method in heavy‐metal extraction from water systems were investigated. EVA did not swell in water, whereas the PU/EVA blend attained a maximum percentage of deionized water uptake of 2.158 mol %. A 3% bentonite/28.5% PU/68.5% EVA composite blend successfully removed 90% of Pb²⁺ from an aqueous solution with an initial concentration of 30 mg/L, whereas 3% bentonite/97% EVA could only extract 7.323% of Pb²⁺ ions. Pb²⁺ adsorption was found to obey the Langmuir adsorption isotherm and pseudo‐second‐order kinetic model. Thermodynamic studies demonstrated that the adsorption was favorable at room temperature and the uptake of Pb²⁺ was mostly by physical adsorption, as also indicated by the value n = 2.449 (where n is an empirical parameter indicating transport mode) from the Freundlich adsorption isotherm. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

One-step hydrothermal synthesis of a green NiCo-LDHs-rGO composite for the treatment of lead ion in aqueous solutions

Herein, we have synthesized a microspherical nickel-cobalt-layered double hydroxides-reduced graphene oxide composite (NiCo-LDHs-rGO) through a one-step hydrothermal method and then used it as an adsorbent for the removal of Pb²⁺ from aqueous solutions. Fourier transform infrared spectrophotometry (FT-IR), field emission scanning electron microscopy (FESEM), mapping elemental analysis, electron dispersive x-ray spectroscopy (EDX), x-ray diffraction analysis (XRD), and the Brunauer–Emmett–Teller (BET) method were used for the characterization of the adsorbent. Factors affecting the adsorption of Pb²⁺ ion such as solution pH, adsorbent dosage, contact time, competing ion, and regeneration were investigated in batch mode by the NiCo-LDHs-rGO. Under optimized conditions based on the Taguchi method (pH = 5.0, adsorbent dosage = 20 mg, and contact time = 30 min), the highest removal percentage was found to be 99.7% for 100 mg L⁻¹ of Pb²⁺. According to the results, NiCo-LDHs-rGO exhibited a high preference for Pb²⁺ over Cu²⁺, Zn²⁺, and Cd²⁺. This adsorbent was regenerated for several cycles (using 0.01 M HCl) with no significant deterioration in performance. Analyses of the adsorption isotherm models revealed that the adsorption of Pb²⁺ follows Freundlich isotherm with a maximum adsorption capacity of 200 mg g⁻¹. Also, the kinetic data confirmed that pseudo second order kinetic equation is the best model for predicting the kinetics. Furthermore, the Simulink modelling illustrated that the adsorption kinetics of Pb²⁺ onto NiCo-LDHs-rGO is done with high accuracy in a continuous stirred-tank reactor. Finally, dual interactions of the effective parameters can be modelled by polynomial equations in MATLAB, and according to the Taguchi model, pH is clearly the most important feature among all effective parameters.     

Highly ordered macroporous γ-alumina prepared by a modified sol-gel method with a PMMA microsphere template for enhanced Pb2+, Ni2+ and Cd2+ removal

The adsorption performance of three-dimensionally ordered macroporous (3DOM) γ-alumina was investigated for enhanced Pb²⁺, Ni²⁺ and Cd²⁺ removal. The synthesis was based on a modified sol-gel method using a colloidal crystal template (CCT) method based on PMMA microspheres. The structure was characterized by means of FTIR spectroscopy and XRD analysis. The three-dimensional structure was examined by scanning electron microscopy, which enabled image analysis that showed significantly low shrinkage (8.77%) after calcination at 800 °C. The influential parameters, including contact time and adsorbent dosage, were investigated in a batch adsorption study. The adsorption equilibrium and kinetic data were found to be in agreement with the Freundlich isotherm for Pb²⁺ removal and the Dubinin-Radushkevich isotherm for Ni²⁺ and Cd²⁺ removal. The time-dependent adsorption was best described by a pseudo-second-order kinetic model and the Weber-Morris model. High adsorption capacities: 95.39, 23.32 and 25.39 mg/g were obtained for Pb²⁺, Cd²⁺ and Ni²⁺ removal at 45 °C, respectively. The existence of interconnected macroporous and mesoporous structures of highly ordered γ-alumina enabled a higher adsorption capacity in comparison with literature data for others alumina-based adsorbents.     

Development of fly ash and iron ore tailing based porous geopolymer for removal of Cu(II) from wastewater

This work aims to verify the feasibility of utilizing iron ore tailing (IOT) in porous geopolymer and intends to broaden the application of porous geopolymer in heavy metal removal aspect. Porous geopolymer was prepared using fly ash as resource material, which was partially replaced by IOT at level of 30%, by weight, with H₂O₂ as foaming agent and removal efficiency, adsorption affecting factors, adsorption isotherms and thermodynamics of Cu²⁺ by the developed porous geopolymer were investigated.The experimental results uncover that the porous amorphous geopolymer was successful synthesized with total porosity of 74.6%. The transformation of fly ash and IOT into foaming geopolymer leads to the formation of porous structure encouraging Cu²⁺ sorption. Batch sorption tests were carried out and geopolymer dosage, Cu²⁺ initial concentration, pH, contact time and temperature were the main concern. Both Langmuir and Freundlich models could explain the adsorption of Cu²⁺ on the porous geopolymer due to the high fitting coefficients. The uptake capacity reaches the highest value of 113.41 mg/g at 40 °C with pH value of 6.0. The thermodynamic parameters ΔHº, ΔSº and ΔGº suggests the spontaneous nature of Cu²⁺ adsorption on porous geopolymer and the endothermic behavior of sorption process.     

Preparation of nano‐structured pig bone hydroxyapatite for high‐efficiency adsorption of Pb2+ from aqueous solution

The nano‐structured hydroxyapatite was prepared from pig bone materials by mineralization. The obtained nano‐structured bone was much better compared to the bone without nanostructure for removing Pb²⁺. The process was investigated under different conditions including contact time, initial Pb²⁺ concentration, and pH. The pseudo‐second‐order kinetic model and Langmuir isotherm model were suitable for describing adsorption process. Moreover, the maximum adsorption capacities of nano‐structured bone and bone without nanostructure were 312.5 and 96.1 mg/g, respectively. Overall, the advantages of excellent adsorption capacity and simple mineralization together with low cost make nano‐structured bone an attractive material for removal of Pb²⁺ from aqueous solution.     

In situ crosslinking of poly(vinyl alcohol)/graphene oxide Nano-composite hydrogel: intercalation structure and adsorption mechanism for advanced Pb(II) removal

Based on the industrialized graphene oxide (GO) product, poly(vinyl alcohol) (PVA)/GO nano-composite hydrogels were prepared through in situ crosslinking by incorporation of N-[(trimethoxysilyl)propyl] ethylenediamine-triacetic acid sodium (CSA) as a compatibilizer. Introduction of CSA led to more efficient grafting of PVA molecules onto GO surface with increasing average layer thickness through covalent and hydrogen bonding interaction, while GO was exfoliated and uniformly distributed in PVA matrix. Addition of appropriate content of GO can improve the storage modulus and the effective crosslinking density (υ_e) of the composite hydrogel, and the network structure with GO as crosslinking point formed, resulting in the remarkable increase of the hydraulic impact resistance, mechanical strength and toughness of the hydrogel. Pb²⁺ adsorption capacity of the hydrogel increased with GO content, while the adsorption belonged to the second-order kinetic model and fitted Langmuir adsorption isotherm model, indicating the homogeneous nature of monolayer chemical adsorption of Pb²⁺. A relatively good reusability of the composite hydrogel beads for Pb²⁺ removal can be achieved.     

Comparative Study of Zn2+, Cd2+, and Pb2+ Removal From Water Solution Using Natural Clinoptilolitic Zeolite and Commercial Granulated Activated Carbon. Equilibrium of Adsorption

Abstract

The aim of this work is to study the effectiveness of regional, low-cost natural clinoptilolitic zeolite tuff in heavy metal ions removal from aqueous solution, through comparative study with commercial granulated activated carbon. The equilibrium of adsorption of Cd²⁺, Pb²⁺, and Zn²⁺ on both adsorbents have been determined at 25, 35, and 45°C in batch mode. The granulated activated carbon has shown around three times higher adsorption capacity for Cd²⁺ and Zn²⁺ than natural zeolite, and almost the same adsorption capacity for Pb²⁺ as the natural zeolite. The metal ion selectivity series Pb²⁺ > Cd²⁺ > Zn²⁺, on a mass basis, has been obtained on both adsorbents. The Langmuir and Freundlich model have been used to describe the adsorption equilibrium. The thermodynamic parameters were calculated from the adsorption isotherm data obtained at different temperatures. The study of the influence of the acidity of the metal ion aqueous solution has shown an increase of metal ion uptake with increase of the pH. The sorption mechanism of Cd²⁺, Pb²⁺, and Zn²⁺ on natural zeolite changes from ion-exchange to ion-exchange and adsorption of metal-hydroxide with increase of the pH from 2 to 6 (and 7 for Zn²⁺). The preliminary cost calculation, based on adsorbents maximum adsorption capacity and their price, have revealed the potential of natural zeolite as an economic alternative to the granulated activated carbon in the treatment of heavy metal polluted wastewater.