Modified superparamagnetic nanocomposite microparticles for highly selective Hg(II) or Cu(II) separation and recovery from aqueous solutions

Removal of Pb2+, CrT, and Hg2+ Ions from Aqueous Solutions Using Amino-Functionalized Magnetic Nanoparticles

In this paper, a circular economy approach with the adsorption and desorption of heavy metal (HM) ions—i.e., lead (Pb2+), chromium (CrT), and mercury (Hg2+)—from aqueous solutions was studied. Specific and selective binding of HM ions was performed on stabilized and amino-functionalized iron oxide magnetic nanoparticles (γ-Fe2O3@NH2 NPs) from an aqueous solution at pH 4 and 7. For this purpose, γ-Fe2O3@NH2 NPs were characterized by thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR), specific surface area (BET), transmission electron microscopy (TEM), EDXS, and zeta potential measurements (ζ). The effects of different adsorbent amounts (mads = 20/45/90 mg) and the type of anions (NO3−, Cl−, SO42−) on adsorption efficiency were also tested. The desorption was performed with 0.1 M HNO3. The results showed improvement of adsorption efficiency for CrT, Pb2+, and Hg2+ ions at pH 7 by 45 mg of g-Fe2O3@NH2 NPs, and the sequence was as follows: CrT > Hg2+ > Pb2+, with adsorption capacities of 90.4 mg/g, 85.6 mg/g, and 83.6 mg/g, respectively. The desorption results showed the possibility for the reuse of γ-Fe2O3@NH2 NPs with HNO3, as the desorption efficiency was 100% for Hg2+ ions, 96.7% for CrT, and 91.3% for Pb2+.

Multifunctional Magnetic Oxide Nanoparticle (MNP) Core-Shell: Review of Synthesis, Structural Studies and Application for Wastewater Treatment

The demand for water is predicted to increase significantly over the coming decades; thus, there is a need to develop an inclusive wastewater decontaminator for the effective management and conservation of water. Magnetic oxide nanocomposites have great potentials as global and novel remediators for wastewater treatment, with robust environmental and economic gains. Environment-responsive nanocomposites would offer wide flexibility to harvest and utilize massive untapped natural energy sources to drive a green economy in tandem with the United Nations Sustainable Development Goals. Recent attempts to engineer smart magnetic oxide nanocomposites for wastewater treatment has been reported by several researchers. However, the magnetic properties of superparamagnetic nanocomposite materials and their adsorption properties nexus as fundamental to the design of recyclable nanomaterials are desirable for industrial application. The potentials of facile magnetic recovery, ease of functionalization, reusability, solar responsiveness, biocompatibility and ergonomic design promote the application of magnetic oxide nanocomposites in wastewater treatment. The review makes a holistic attempt to explore magnetic oxide nanocomposites for wastewater treatment; futuristic smart magnetic oxides as an elixir to global water scarcity is expounded. Desirable adsorption parameters and properties of magnetic oxides nanocomposites are explored while considering their fate in biological and environmental media.

Removal of Hg2+ by carboxyl-terminated hyperbranched poly(amidoamine) dendrimers grafted superparamagnetic nanoparticles as an efficient adsorbent

In this research, carboxyl-terminated hyperbranched poly(amidoamine) dendrimers grafted superparamagnetic nanoparticles (CT-HPMNPs) with core-shell structure were synthesized by the chemical co-precipitation method, the core of superparamagnetic iron oxide nanoparticles and a shell of polyamidoamines (PAMAM) and carboxyl groups, as a novel adsorbent for removing Hg²⁺ from aqueous systems. The surface of the particles was modified by 3-(aminopropyl) triethoxysilane, and finally, PAMAM and carboxyl dendrimers were grown on the surface up to 5.5 generation. The synthesized polymer was characterized physically and morphologically using different techniques. Also, they were evaluated in terms of adsorption capacity to remove inorganic pollutants of Hg²⁺, selectivity, and reusability. The adsorption mechanism Hg²⁺ onto CT-HPMNPs was investigated by single-step and two-step isotherms that the adsorption capacity of Hg²⁺ obtained 72.3 and 32.88 mg g^-1 respectively at pH 5, adsorbent dosage 2 g L^-1, Hg²⁺ initial concentrations 20 mg L^-1, contact time 60 min, and temperature of 298 K by CT-HPMNPs. Also, the kinetics of Hg²⁺ followed the pseudo-second-order model and adsorption isotherms of Hg²⁺ onto CT-HPMNPs were fitted well by Freundlich (as a single-step) and two-step adsorption models with a correlation coefficient of 0.9997 and 0.9999 respectively. The results showed a significant potential of Hg²⁺ ions removing from industrial wastewater and spiked water by CT-HPMNPs.

Removal of mercury(II) from contaminated water by gold-functionalised Fe3O4 magnetic nanoparticles

Fe₃O₄ nanoparticles were prepared by co-precipitation of Fe²⁺ and Fe³⁺ and then modified with Au to produce an effective adsorbent (Fe₃O₄/Au) for aqueous Hg(II) in contaminated water. Rietveld refinement on the XRD pattern confirmed that the Fe₃O₄/Au was synthesised. Mössbauer spectra exhibited broad and asymmetric resonance lines with two sextets which can be assigned to tetrahedral Fe³⁺; and octahedral Fe³⁺/Fe²⁺. The quantitative analysis of magnetite confirms that the sample shows around 3 wt.% Au and 97 wt.% partially oxidised Fe₃O₄. High surface area: 121 m² g^-1, average pore sizes: 6.3 nm and pore volume: 1.64 cm³ g^-1. The kinetics data were better fitted with a pseudo-second-order and Dubinin-Radushkevich isotherm suggests the Hg(II) adsorption onto Fe₃O₄/Au nanoparticles was mainly by chemical adsorption forming complex with the Au metal immobilised on Fe₃O₄ surfaces. Adsorption capacity of 79.59 mg g^-1. Ionic strength and co-existing ions had a slight influence on the adsorption capacity.

Monolayers of an organosilane on magnetite nanoparticles for the fast removal of Cr(VI) from water

Monolayers of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane have been established on magnetite nanoparticles to develop a novel magnetic adsorbent for fast decontamination of hexavalent chromium (Cr(VI)) from water. Results indicated that monolayer adsorption of the silane from water took place at low concentrations (<300 mg/L) and around 100% surface coverage was obtained at temperatures ≥90°C. The hydrolysed silane was anchored to the magnetite surface through condensation reactions between its silanol groups and the surface hydroxyl groups of magnetite. The functional amine groups were protonated by acid treatment for adsorbing Cr(VI). The monolayer of the silane on magnetite (MSM) with approximately 100% surface coverage showed extremely rapid adsorption kinetics for Cr(VI), such that the process was complete within 1 min. This enables the treatment of large amounts of sewage per unit time. The adsorption capacity for Cr(VI) was 8.0 mg/g, as estimated from the Langmuir isotherm model. The saturation magnetization of the MSM reached 64.16 emu/g, allowing easy magnetic recovery from water. In the presence of up to 50-fold molar excesses of chloride and nitrate anions, little effect on Cr(VI) removal was seen, but moderate and large impacts were observed with sulphate and hydroxyl anions, respectively. Desorption of adsorbed Cr(VI) and regeneration of the MSM were successfully achieved by NaOH and HCl treatments to deprotonate and protonate the amine groups, respectively. By selecting a silane with suitable functional groups, the surface properties may be tailored for a particular pollutant.

Simple synthesis and characterization of l-Cystine functionalized δ-FeOOH for highly efficient Hg(II) removal from contamined water and mining waste

l-Cystine functionalized δ-FeOOH nanoparticles (Cys-δ-FeOOH) were prepared by a cheap and straightforward method for using as an adsorbent of Hg(II) in aqueous solution. X-ray diffraction (XRD), attenuated total reflectance infrared spectroscopy (ATR-IR), and Raman spectroscopy confirmed that Cys-δ-FeOOH was successfully synthesized. Cys-δ-FeOOH with 14 nm crystal size, 34 m² g^-1 surface area, and 9 nm pore size were produced. The functionalization of the δ-FeOOH surface with cysteine decreases the point of zero charge of the iron oxyhydroxide from 8.4 in δ-FeOOH to 5.7 in Cys-δ-FeOOH, which is beneficial for the adsorption of Hg(II) near neutral pH. The maximum Hg(II) adsorption capacity of the δ-FeOOH and Cys-δ-FeOOH at pH 7 were found to be 35 mg g^-1 and 217 mg g^-1, respectively. The kinetics data were best fitted by a pseudo-second-order model, suggesting chemical adsorption on the surface and pores of Cys-δ-FeOOH nanoparticles. Finally, δ-FeOOH and Cys-δ-FeOOH filters were constructed for purifying mercury-contaminated water. The filters were highly efficient to treat mercury-contaminated water from a Brazilian river, reducing the concentration of mercury in water to values below the allowed limits by the current legislation.

Supraparticles: Functionality from Uniform Structural Motifs

Under the right process conditions, nanoparticles can cluster together to form defined, dispersed structures, which can be termed supraparticles. Controlling the size, shape, and morphology of such entities is a central step in various fields of science and technology, ranging from colloid chemistry and soft matter physics to powder technology and pharmaceutical and food sciences. These diverse scientific communities have been investigating formation processes and structure/property relations of such supraparticles under completely different boundary conditions. On the fundamental side, the field is driven by the desire to gain maximum control of the assembly structures using very defined and tailored colloidal building blocks, whereas more applied disciplines focus on optimizing the functional properties from rather ill-defined starting materials. With this review article, we aim to provide a connecting perspective by outlining fundamental principles that govern the formation and functionality of supraparticles. We discuss the formation of supraparticles as a result of colloidal properties interplaying with external process parameters. We then outline how the structure of the supraparticles gives rise to diverse functional properties. They can be a result of the structure itself (emergent properties), of the colocalization of different, functional building blocks, or of coupling between individual particles in close proximity. Taken together, we aim to establish structure-property and process-structure relationships that provide unifying guidelines for the rational design of functional supraparticles with optimized properties. Finally, we aspire to connect the different disciplines by providing a categorized overview of the existing, diverging nomenclature of seemingly similar supraparticle structures.

Introduction of Molecular Building Blocks to Improve the Stability of Metal-Organic Frameworks for Efficient Mercury Removal

With expanding human needs, many heavy metals were mined, smelted, processed, and manufactured for commercialization, which caused serious environmental pollutions. Currently, many adsorption materials are applied in the field of adsorption of heavy metals. Among them, the principle of many mercury adsorbents is based on the interaction between mercury and sulfur. Here, a S-containing metal-organic framework NENU-400 was synthesized for effective mercury extraction. Unfortunately, the skeleton of NENU-400 collapsed easily when exposed to the mercury liquid solution. To improve the stability, a synthetic strategy installing molecular building blocks (MBBs) into the channels was used. Modified by the MBBs, a more stable nanoporous framework was synthesized, which not only exhibits a high capacity of saturation mercury uptake but also shows high selectivity and efficient recyclability.

Hydrophilic and positively charged polyethylenimine-functionalized mesoporous magnetic clusters for highly efficient removal of Pb(II) and Cr(VI) from wastewater

We develop mesoporous magnetic clusters (MMCs) functionalized with hydrophilic branched polyethylenimine (b-PEI), later called b-MG, and MMCs functionalized with positively charged b-PEI (p-MG). These materials efficiently remove Pb(II) and Cr(VI) from wastewater. Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis, and nitrogen adsorption-desorption analysis results clearly indicate that hydrophilic b-PEI and positively charged b-PEI are successfully attached to the MMC surfaces. Wide-angle X-ray diffraction, high-resolution transmission electron microscopy, and field-emission scanning electron microscopy analyses confirm that the crystal structures and morphologies of the MMCs are maintained well even when wet chemical modification processes are used to introduce hydrophilic b-PEI and positively charged b-PEI to the MMC surfaces. Langmuir and Sips isotherm models are applied to describe Pb(II) adsorption behavior of the b-MG and Cr(VI) adsorption behavior of the p-MG. The isotherm models indicate that the maximum adsorption capacities of b-MG and p-MG, respectively, are 216.3 and 334.1 mg g^-1, respectively. These are higher than have previously been found for other adsorbents. In reusability tests, using magnetic separation and controlling the pH, the Pb(II) recovery efficiency of the b-MG is 95.6% and the Cr(VI) recovery efficiency of the p-MG is 68.0% even after the third cycle.

Synthesis of Ce(III)-doped Fe3O4 magnetic particles for efficient removal of antimony from aqueous solution

Aqueous antimony (Sb) pollution from human activity is of great concern in drinking water due to its adverse health effect. Magnetic Fe₃O₄ particles, with high separation ability from solution, have been considered as a low-cost Sb adsorbent for contaminants. However, the limited adsorption capacity has restricted its practical application. In this study, a solvothermal approach was developed for doping Ce(III) into Fe₃O₄, thereby increasing the adsorption efficacy for both Sb(III) and Sb(V). In contrast to un-doped Fe₃O₄, the adsorption capacity towards Sb(III) and Sb(V) in Ce-doped materials increased from 111.4 to 224.2mg/g and from 37.2 to 188.1mg/g at neutral pH, respectively. Based on the combined results of XPS, XRD, and FTIR, it confirmed that Ce atom successfully doped into the Fe₃O₄ structure, resulting in the decreased particle size, increased the surface area, and isoelectric point. Furthermore, the vibrating sample magnetometer (VSM) results showed that the Ce doping process had some side effects on the primitive magnetic property, but remaining the high separation potential during water treatment. According to the high removal efficiency and magnetic property, the Ce-doped Fe₃O₄ of great simplicity should be a promising adsorbent for aqueous Sb removal.

Pilot-scale removal and recovery of dissolved phosphate from secondary wastewater effluents with reusable ZnFeZr adsorbent @ Fe3O4/SiO2 particles with magnetic harvesting

Advanced nanocomposite magnetic particles functionalized with ZnFeZr-adsorbent are developed, characterized and tested for the removal and recovery of phosphate directly from spiked secondary wastewater effluent (∼10 mg/L PO₄-P). The phosphate loaded particles can be extracted from the liquid phase via magnetic separation, regenerated in a NaOH solution where phosphate desorption takes place, and reused in numerous cycles. Laboratory experiments demonstrate their reusability and stability in 60 consecutive adsorption/desorption runs where under optimal conditions > 90% total P-recovery efficiency is reached. In addition, pilot tests are performed to verify the proof-of-concept by upscaling the technology and maintain high efficiency of phosphate removal and recovery after treating 1.5 m³ wastewater in 20 cycles. Effluent concentrations <0.05 mg/L PO₄-P can be achieved in the treated wastewater. The reclaimed desorption solution is concentrated with phosphate ions through its repetitive application, attaining up to 38-times enrichment (∼380 mg/L PO₄-P) compared to the initial concentration in wastewater. The P-rich eluate is used as a source for subsequent precipitation of a solid fertilizer product such as struvite.

Adsorption of Cu(ii) ions in aqueous solution by aminated lignin from enzymatic hydrolysis residues

Aminated lignin (AL) has been prepared by a Mannich reaction for the removal of Cu(ii) ions from aqueous solution.

Superparamagnetic Composites Based on Ionic Resin Beads/CaCO3 /Magnetite

The preparation of superparamagnetic composites obtained by CaCO₃ mineralization from supersaturate aqueous solutions is presented. The preparation was conducted in the presence of oleic acid stabilized magnetite nanoparticles as a water-based magnetic fluid and insoluble templates as gel-like cross-linked polymeric beads. The presence of the magnetic particles in the composites provides a facile way for external manipulation using a permanent magnet, thus allowing the separation and extraction of magnetically modified materials. Two ion exchangers based on divinylbenzene/ethyl acrylate/acrylonitrile cross-linked copolymer-a cation ion exchanger (CIE) and an amphoteric ion exchanger (AIE)-were used, as well as different addition orders of magnetite and CaCO₃ crystals growth precursors. The morphology of the composites was investigated by SEM, the polymorphs content by X-ray diffraction, and the thermal stability by thermogravimetric analysis. Polymer, CaCO₃ , and magnetite in the composite particles were shown to be present by energy dispersive X-ray (EDX), XPS, and TEM. The sorption capacity for Cu^II ions was tested, as compared to samples prepared without magnetite.

Superparamagnetic Luminescent MOF@Fe₃O₄/SiO₂ Composite Particles for Signal Augmentation by Magnetic Harvesting as Potential Water Detectors

Herein, we present the generation of a novel complex particle system consisting of superparamagnetic Fe3O4/SiO2 composite microparticle cores, coated with luminescent metal-organic frameworks (MOFs) of the constitution (∞)(2)[Ln2Cl6(bipy)3]·2bipy (bipy = 4,4′-bipyridine) that was achieved by intriguing reaction conditions including mechanochemistry. The novel composites combine the properties of both constituents: superparamagnetism and luminescence. The magnetic properties can be exploited to magnetically collect the particles from dispersions in fluids and, by gathering them at one spot, to augment the luminescence originating from the MOF modification on the particles. The luminescence can be influenced by chemical compounds, e.g., by quenching observed for low concentrations of water. Thus, the new composite systems present an innovative concept of property combination that can be potentially used for the detection of water traces in organic solvents as a magnetically augmentable, luminescent water detector.

Superparamagnetic nalidixic acid grafted magnetite (Fe3O4/NA) for rapid and efficient mercury removal from water

A new nanomaterial, nalidixic acid grafted magnetite (Fe₃O₄/NA), was synthesized via a chemical reaction with nano sized magnetite particles.

Novel polyazamacrocyclic receptor decorated core–shell superparamagnetic microspheres for selective binding and magnetic enrichment of palladium: synthesis, adsorptive behavior and coordination mechanism

Novel core–shell superparamagnetic microspheres decorated with polyazamacrocyclic receptors for selective enrichment of palladium.

Hierarchical core–shell structured Fe3O4@NiSiO3 magnetic microspheres: preparation, characterization, and adsorption of methylene blue from aqueous solution

Core–shell structured Fe₃O₄@NiSiO₃ magnetic microspheres are synthesised and possess high porosity and magnetic properties, which allow the microspheres to exhibit efficient adsorption of methylene blue and convenient separation from wastewater.

Chemical Insight into the Adsorption of Chromium(III) on Iron Oxide/Mesoporous Silica Nanocomposites

Magnetic iron oxide/mesoporous silica nanocomposites consisting of iron oxide nanoparticles embedded within mesoporous silica (MCM-41) and modified with aminopropyl functional groups were prepared for application to Cr(III) adsorption followed by magnetic recovery of the nanocomposite materials from aqueous solution. The composite materials were extensively characterized using physicochemical techniques, such as powder X-ray diffraction, thermogravimetric and elemental analysis, nitrogen adsorption, and zeta potential measurements. For aqueous Cr(III) at pH 5.4, the iron oxide/mesoporous silica nanocomposite exhibited a superior equilibrium adsorption capacity of 0.71 mmol/g, relative to 0.17 mmol/g for unmodified mesoporous silica. The aminopropyl-functionalized iron oxide/mesoporous silica nanocomposites displayed an equilibrium adsorption capacity of 2.08 mmol/g, the highest adsorption capacity for Cr(III) of all the materials evaluated in this study. Energy-dispersive spectroscopy (EDS) with transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) experiments provided insight into the chemical nature of the adsorbed chromium species.

Removal of Hg(II) by poly(1-vinylimidazole)-grafted Fe3O4@SiO2 magnetic nanoparticles

Fe3O4@SiO2 magnetic nanoparticles modified by grafting poly(1-vinylimidazole) oligomer (FSPV) was fabricated as a novel adsorbent to remove Hg(II) from water. Fourier transform infra-red spectroscopy confirmed the successful grafting of oligomer, and thermogravimetric analysis showed FSPV had a high grafting yield with organic content of 22.8%. Transmission electron microscopy image displayed that FSPV particles were polymer-coated spheres with size of 10-20 nm. With saturation magnetization of 44.7 emu/g, FSPV particles could be easily separated from water with a simple magnetic process in 5 min. The Hg(II) adsorption capacity of FSPV was found to be 346 mg/g at pH 7 and 25 °C in 10 mM NaCl. Moreover, the removal of Hg(II) by FSPV was not obviously affected by solution pH (from 4 to 10) or humic acid (up to 8 mg/L as TOC). The presence of seven common ions including Na(+), K(+), Ca(2+), Mg(2+), Cl(-), NO3(-), and SO4(2-) (up to 100 mM ionic strength) slightly increased the adsorption of Hg(II) by FSPV. X-ray photoelectron spectroscopy analysis revealed that the N atom of the imidazole ring was responsible for the bonding with Hg(II), whereas the bonding of Hg with N did not result in cleavage of Hg-Cl bond in HgCl2 and HgClOH. The regeneration of Hg(II)-loaded FSPV could be achieved with 0.5 M HCl rapidly in 10 min, and the removal of Hg(II) maintained above 94% in five consecutive adsorption-desorption cycles. Therefore, FSPV could serve as a promising adsorbent for Hg(II) removal from water.

Reversible magnetic mercury extraction from water

Magnetic carbon-coated cobalt nanoparticles functionalized with polyethyleneimine proved to be highly effective and selective for the detoxification of mercury ions from aqueous solutions.

Mechanochemical surface functionalisation of superparamagnetic microparticles with in situ formed crystalline metal-complexes: a fast novel core–shell particle formation method

An innovative mechanochemical method is reported for the in situ formation of crystalline metal-complexes on the surface of superparamagnetic nanocomposite microparticles.

Hydrothermal synthesis of hierarchical core–shell manganese oxide nanocomposites as efficient dye adsorbents for wastewater treatment

Hierarchical core–shell manganese oxide nanocomposites (Fe₃O₄@MnO₂ and Fe₂O₃@MnO₂) are synthesized via a hydrothermal process and showed good adsorption capability for wide applications.

Hierarchically structured manganese oxide-coated magnetic nanocomposites for the efficient removal of heavy metal ions from aqueous systems

In this study, hierarchical MnO2-coated magnetic nanocomposite (Fe3O4/MnO2) was synthesized by a mild hydrothermal process, and its application for removing heavy metal ions from contaminated water systems was examined. Structural characterization showed that the Fe3O4 nanoparticle core was coated with amorphous MnO2 shell with flowerlike morphology. The as-prepared nanocomposite had a large surface area and high magnetic saturation value, which ensured its good sorption ability and convenience of separation. Fe3O4/MnO2 exhibited a greatly improved removal capacity toward four different heavy metals (Cd(II), Cu(II), Pb(II), and Zn(II)) compared to unmodified Fe3O4 nanoparticles. The adsorption property of Fe3O4/MnO2 was studied with Cd(II) in more detail. The sorption equilibrium data were well fitted to the Langmuir model, and the maximum adsorption capacity toward Cd(II) was 53.2 mg g(-1). Fe3O4/MnO2 retained over 80% of its adsorption capacity under various solution conditions that are typically encountered in natural waters. This nanocomposite was easily recovered and reused through consecutive adsorption-desorption experiments with the assistance of an external magnetic field. Overall, the findings propose that Fe3O4/MnO2 could be used as an effective recyclable adsorbent for heavy metal ions.

Phosphate recovery from wastewater using engineered superparamagnetic particles modified with layered double hydroxide ion exchangers

An innovative nanocomposite material is proposed for phosphate recovery from wastewater using magnetic assistance. Superparamagnetic microparticles modified with layered double hydroxide (LDH) ion exchangers of various compositions act as phosphate adsorbers. Magnetic separation and chemical regeneration of the particles allows their reuse, leading to the successful recovery of phosphate. Based upon the preliminary screening of different LDH ion exchanger modifications for phosphate selectivity and uptake capacity, MgFe-Zr LDH coated magnetic particles were chosen for further characterization and application. The adsorption kinetics of phosphate from municipal wastewater was studied in dependence with particle concentration, contact time and pH. Adsorption isotherms were then determined for the selected particle system. Recovery of phosphate and regeneration of the particles was examined via testing a variety of desorption solutions. Reusability of the particles was demonstrated for 15 adsorption/desorption cycles. Adsorption in the range of 75-97% was achieved in each cycle after 1 h contact time. Phosphate recovery and enrichment was possible through repetitive application of the desorption solution. Finally, a pilot scale experiment was carried out by treating 125 L of wastewater with the particles in five subsequent 25 L batches. Solid-liquid separation on this scale was carried out with a high-gradient magnetic filter (HGMF).

Biosorption of multifold toxic heavy metal ions from aqueous water onto food residue eggshell membrane functionalized with ammonium thioglycolate

A new biosorbent material from eggshell membrane was synthesized through thiol functionalization, which is based on the reduction of disulfide bonds in eggshell membrane by ammonium thioglycolate. The thiol-functionalized eggshell membrane was characterized, and its application as an adsorbent for removal of Cr(VI), Hg(II), Cu(II), Pb(II), Cd(II), and Ag(I) from aqueous water has been investigated. The experimental results revealed that the adsorption abilities of the thiol-functionalized eggshell membrane toward Cr(VI), Hg(II), Cu(II), Pb(II), Cd(II), and Ag(I) improved 1.6-, 5.5-, 7.7-, 12.4-, 12.7-, and 21.1-fold, respectively, compared with that of the eggshell membrane control. The adsorption mechanism and adsorption performance, including the adsorption capacity and the kinetics of the thiol-functionalized eggshell membrane for the target heavy metals, were investigated. The effects of solution pH, coexisting substances, and natural water matrices were studied. The thiol-functionalized eggshell membrane can be used as column packing to fabricate a column for real wastewater purification.