Binary Component Systems Research Articles

Removal of arsenic and fluoride ions from aqueous solutions using electronic waste-derived adsorbent

Printed Circuit Boards are the fundamental component of almost every electronic device with usage intensifying at an average rate of 8.7 %. However, this leads to a generation of 45 million tons of electronic waste (E-waste) annually posing significant and concerning environmental risks. Recycling these waste printed circuit boards (PCBs) is vital, in terms of environmental pollution, prevention and resource recycling. Activating these non-metallic fractions of the printed circuit boards results in the development of unique textural properties and functionalities which resemble aluminosilicates; confirmed by FTIR, XRD, XPS, XRF, and TGA and could potentially be applied for the uptake of Fluoride and Arsenate. In this study, Activated Non-metallic fraction of the Printed Circuit Boards (A-NMP) was used to investigate various physio-chemical parameters, including contact time, pH, adsorbent dose, and initial concentration to optimize the reaction conditions for the uptake of F− and As(V) from aqueous solutions and, compared its adsorption capacity with other natural and synthetic aluminosilicate. The maximum adsorption capacity comes out to be 4.33 mg g−1 and 4.65 μg g−1 for F− and As(V) and best fit to Langmuir and Freundlich adsorption isotherms, respectively. Kinetic modelling reveals that the adsorption of F− follows pseudo-first-order kinetics whereas, As(V) follows pseudo-second-order kinetics. Moreover, Intra-particle diffusion revealed a chemisorption-controlled process for both the adsorbates. Furthermore, in a binary component system the F− and As(V) showed the maximum percentage removal of 92 % and 76 %, respectively at pH 5, and best fit to Langmuir adsorption isotherm.

A parameter estimation method for chromatographic separation process based on physics-informed neural network

Chromatographic separation processes are most often modeled in the form of partial differential equations (PDEs) to describe the complex adsorption equilibria and kinetics. However, identifying parameters in such a model requires substantial computational effort. In this work, a novel parameter estimation approach using a Physics-informed Neural Network (PINN) model is developed and tested for a binary component system. Numerical accuracy of our PINN model is confirmed by validating its simulations against those of the finite element method (FEM). Furthermore, model parameters in the kinetic model are estimated by the PINN model with sufficient accuracy from the observed data at the column outlet, where parameter fitting error can be reduced by up to 35.0 % from the conventional method. In a comparison with the conventional numerical method, our approach can reduce the computational time by up to 95 %. The robustness of the PINN model has also been demonstrated by estimating model parameters from noisy artificial experimental data.

Hydrophobic CHA-ZIFs with a junctional trap between cha and d6r cages for adsorption of 2,3-butanediol in aqueous solution

Hydrophobic CHA-ZIFs with a junctional trap between cha and d6r cages for adsorption of 2,3-butanediol in aqueous solution

Azadirachta indica leaf extract based green-synthesized ZnO nanoparticles coated on spent tea waste activated carbon for pharmaceuticals and personal care products removal

Pharmaceuticals and personal care products (PPCPs) are emerging contaminants in aqueous systems, posing threat to both human health and environment. In prior research, predominant focus has been on examining various adsorbents for removing PPCPs from single-pollutant systems. However, no study has delved into simultaneous adsorption of PPCPs multi-pollutant mixture. This study evaluates performance of Azadirachta indica leaf extract-based green-synthesized ZnO nanoparticles coated on spent tea waste activated carbon (ZTAC) for removing sulfadiazine (SZN) and acetaminophen (ACN). Adsorption investigations were conducted in single-component (ACN/SZN) and binary-component (ACN + SZN) systems. The synthesized ZTAC was characterized using SEM, XRD, FTIR, EDX, porosimetry and pHpzc analysis. The study examines impact of time (1–60 min), dose (0.2–4 g/L), pH (2–12) and PPCPs concentration (1–100 mg/L) on ACN and SZN removal. Various kinetic and isotherm models were employed to elucidate mechanisms involved in sorption of PPCPs. Furthermore, synergistic and antagonistic aspects of sorption process in multi-component system were investigated. ZTAC, characterized by its crystalline nature and surface area of 980.85 m2/g, exhibited maximum adsorption capacity of 47.39 mg/g for ACN and 34.01 mg/g for SZN under optimal conditions of 15 min, 3 g/L and pH 7. Langmuir isotherm and pseudo-second-order kinetic model best-fitted the experimental data indicating chemisorption mechanism. Removal of ACN and SZN on ZTAC demonstrated synergistic nature, signifying cooperative adsorption. Overall, valorization of ZTAC offers effective and efficient adsorbent for elimination of PPCPs from wastewater.

Removal of dyes using chemically modified elephant grass in single and binary-component system

The present study investigated the potential use of citric acid-treated Elephant grass (Pennisetum purpureum), as an adsorbent for the removal of various dyes (Congo red, Erichrome black T, methyl red, and thymol blue) from aqueous solutions. The effects of initial concentration, adsorbent dosage, and temperature on the adsorption capacity of the dyes were evaluated. The results showed that Pennisetum purpureum had a high adsorption capacity for all dyes, with maximum adsorption efficiencies ranging from 74% to 98.92%, depending on the dye type and experimental conditions. The highest adsorption efficiency was recorded at 10 mg/L initial concentration for most of the dyes. The optimum adsorbent dosage was found to be 0.3 g for all dyes, except for Erichrome black T, which showed maximum adsorption capacity at 0.2 g. The maximum adsorption capacity for all dyes was observed at a temperature of 60°C, except for methyl red and thymol blue, which showed maximum adsorption at temperatures lower than 60°C. Overall, the results indicate that citric acid-treated Pennisetum purpureum has great potential as an effective and sustainable adsorbent for the removal of various dyes from wastewater.

Sponge-like biodegradable polypyrrole-modified biopolymers for selective adsorption of basic red 46 and crystal violet dyes from single and binary component systems

Recently, several researchers have been trying to reduce the ecological effects of water pollution by considering the use of biodegradable materials that prevent the generation of secondary pollution in our environment and enable water reuse. Here, new biodegradable hydrogels based on alginate (Alg), gelatin (Gel) and polypyrrole (PPy) were successfully implemented to remove two known highly toxic cationic dyes from wastewater. The design process was performed in two steps: in-situ polymerization of polypyrrole within the Alg/Gel mixture, followed by hydrogel formation. Biocomposites showed promising efficacy for the removal of both basic red 46 (BR46) and crystal violet (CV) dyes from real and demineralized water samples. However, Alg-Gel-PPy hydrogel showed better selectivity for BR46 than for CV as compared to the pristine Alg-Gel hydrogel. Adsorption of both pollutants on biocomposite hydrogel beads followed the Langmuir isotherm and pseudo-second order kinetic models. Besides, the highest adsorption capacities (125 mg g−1 for BR46 and 88.5 mg g−1 for CV) were obtained for the Alg-Gel-PPy hydrogel, compared with those determined for PPy-free hydrogel (103.09 mg g−1 for BR46 and 86.96 mg g−1 for CV) and remained at a satisfactory level for five adsorption-desorption cycles. Finally, the obtained hydrogels showed excellent biodegradability by natural soil microorganisms, with 91 % decomposition.

Competitive adsorption of VOCs (benzene, xylene and ethylbenzene) with Fe3O4@SiO2-NH@BENZOPHENONE magnetic nanoadsorbents

Volatile organic compounds (VOCs), which are toxic, mutagenic and carcinogenic, are considered a critical factor for air pollution and cause serious harm to the eco-environment and human health. In this study, Fe3O4, Fe3O4@SiO2-NH2, Fe3O4@SiO2-NH@BENZOFENONE were synthesized as new magnetic nanoadsorbents (MNAs) and used for the first time in the removal of gas-phase benzene, xylene and ethylbenzene. The synthesised MNAs were characterized by SEM-EDS, TEM, FTIR, XRD, VSM, TGA and BET analyses. The characterization results showed that the MNAs have mesoporous structure, type IV physioresorption and type H3 hysteresis loop character. In order to clarify the comparative and competitive adsorption behaviour, the adsorption capacity of Fe3O4@SiO2-NH@BENZOFENONE MNA was found to be in the order of xylene > ethylbenzene > benzene in both single, binary and ternary component systems. The adsorption kinetics of benzene, xylene and ethylbenzene with Fe3O4@SiO2-NH@BENZOFENONE MNA were found to be governed by multistep mechanisms. Fe3O4@SiO2-NH@BENZOFENONE MNA showed reuse efficiencies of 83.07%, 84.35% and 82.99% after 5 cycles for benzene, xylene and ethylbenzene respectively. In the framework of the results, Fe3O4@SiO2-NH@BENZOPHENONE MNA, which has a high potential in terms of both adsorption capacity and reuse efficiency, is proposed as a promising adsorbent for the efficient removal of benzene, xylene and ethylbenzene.

Enhanced removal and stepwise recovery of inorganic and organic micropollutants from water using novel graphene oxide doped multifunctional β−cyclodextrin chitosan polymer

Herein, graphene oxide (GO) was successfully functionalized on the multifunctional β−cyclodextrin chitosan polymer through EDTA crosslinking (GO@CS−EDTA−β−CD) for the adsorption of toxic inorganic and organic micropollutants from water. This unique adsorbent possesses important adsorptive features from each component: chitosan works as a backbone of the polymer chain, β−CD cavities adsorb the organic micropollutants via the host-guest inclusion complexation, EDTA acts as a crosslinker and provides complexation sites for heavy metal ions and GO can interact with both organic and inorganic micropollutants. After complete characterization, the polymer were explored on the adsorption of inorganic micropollutants (i.e., Hg(II), Pb(II), Cu(II) and Ni(II)) and organic one (i.e., methylene blue, MB) under different experimental conditions. In monocomponent systems, the adsorption followed the pseudo-second order (PSO) kinetics for both heavy metals and MB dye. The adsorption isotherms of heavy metals and MB followed the Langmuir and Sips models, respectively. The maximum adsorption capacities were found to be 364.90 ± 15.20, 287.40 ± 10.0, 130.40 ± 6.50, 98.90 ± 3.10, 158.40 ± 5.10 mg g−1 for Hg(II), Pb(II), Cu(II), Ni(II) and MB, respectively. In binary component systems, dye adsorption was not affected by metal ions, while the adsorption efficiency for metal ions was increased by the MB presence: possibly due to synergism. Additionally, the prepared adsorbent showed good efficiency without any significant loss in adsorption capacity even after six continuous regeneration cycles, confirming its superior reusability and stability. In short, excellent removal efficiencies for the metal ions and MB at environmental levels in model textile effluent, synthetic acid mine water make the adsorbent promising in treating water contaminated by heavy metals and/or dyes.

Simultaneous Adsorptive/photocatalytic Removal of Organic Dyes and Hexavalent Chromium in Single and Binary Component Systems by Manganese Ferrite Nanoparticles

Background: As a major source of pollutant, the effluents of dye based industries are mostly associated with several toxic heavy metals. Limited efforts have been made on simultaneous removal of both dyes and heavy metals from these effluents through adsorption/photocatalysis processes. Spinel ferrites with narrow band gap and high stability are suitable for further exploitation in this regard. Objective: Synthesis and characterisation of manganese ferrite nanoparticle and to assess its efficiency towards removal of organic dyes and hexavalent chromium in single and binary component systems are the objectives of this study. Methods: Manganese ferrite nanoparticle (MF NPs), prepared by coprecipitation, was characterised systematically by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, UV-Visible diffuse reflectance and magnetic measurement. Adsorptive and photocatalytic performances of the material under visible light were evaluated using aqueous solutions of different dyes and Cr(VI). Results: Characterisation by various techniques revealed the formation of cubic MF nanoparticles with narrow band gap (1.78 eV) and moderate saturation magnetization (38.5 emu/g). In comparison, the anionic dyes and Cr(VI) were better adsorbed on MF, while photoactivity was more pronounced in the case of cationic dye. Conclusion: MF NPs displayed potential for photo-degradation/reduction of different dyes and Cr(VI) individually or simultaneously under visible light. The catalyst can be recovered magnetically from the reaction mixture for recycling and further use.

Functionalized ionic liquids based on DODGA with enhanced Eu(III)/U(VI) separation efficiency in highly acidic environment

Lanthanides/actinides separation is of importance in many modern industrial engineering fields, e.g. the circulation of the nuclear fuel and rare earth. N,N-dioctyl diglycol amic acid (briefly as DODGA) is known as an effective extractant for extraction of rare earth metal. In this work, two extractants, [N1888][DODGA] and [N4444][DODGA], were developed by using quaternary ammonium as cations and DODGA as anion. The resultant ionic liquids were used to separate europium from europium-uranium binary component system. The influence of several factors (nitric acid concentration, contact time, temperature, metal ions, extractant concentration, salting agent concentration and stripping) were analyzed. The coordination chemistry of Eu(III) with [N1888][DODGA] and [N4444][DODGA] were investigated by the mole-ratio method. The experimental results confirmed that the separation factors (SF) of Eu(III)/U(VI) were reached 55.44 and 60.35 for [N1888][DODGA] and [N4444][DODGA]. The stoichiometry of the complex of Eu(III) and [N1888][DODGA] or [N4444][DODGA] were determined as 1:3. Excellent extraction of the target metals and prominent separation factors using these ionic liquids showed that they were viable to separate lanthanides from actinides.

Synergistic effect in simultaneous removal of cationic and anionic heavy metals by nitrogen heteroatom doped hydrochar from aqueous solutions

Industrial wastewater typically contains both cationic and anionic heavy metals; therefore, their simultaneous removal must be considered to ensure environmental sustainability. Herein, nitrogen heteroatom (N) doped hydrochar derived from corncob was prepared via facile NH4Cl-aided hydrothermal carbonization and used for the simultaneous adsorption of divalent copper (Cu(II)) and hexavalent chromium (Cr(VI)) in aqueous solutions. During hydrothermal carbonization, NH4Cl played a vital role as the porogen and N dopant, which contributed to the efficient adsorption affinity toward coexisting Cu(II) and Cr(VI). The theoretical maximum adsorption capacities of the N-doped hydrochar were determined to be 1.223 mmol/g for Cu(II) and 1.995 mmol/g for Cr(VI), which were much better than those of the pristine hydrochar. Furthermore, in the binary-component system, the synergistic effect between Cu(II) and Cr(VI) significantly promoted the adsorption affinity of N-doped hydrochar, resulting in adsorption capacities for Cu(II) and Cr(VI) 9.48 and 1.92 times higher than those of the single-component system, respectively. A series of adsorption experiments and spectroscopic analyses demonstrated that multiple mechanisms, including electrostatic shielding, cation bridging, and redox reactions, mutually contributed to the synergistic effect in the adsorption of coexisting Cu(II) and Cr(VI). Overall, the N-doped hydrochar proved to be effective in simultaneously removing both cationic and anionic heavy metal pollutants.

Selective adsorption of Cr(III) over Cr(VI) by starch-graft-itaconic acid hydrogels

This work investigates the applicability of starch-graft-itaconic acid hydrogels in the adsorption of Cr(III) and Cr(VI) in single- and binary-component systems. Batch adsorption studies were conducted at room temperature for 24 h using 0.1 g of hydrogels to explore the effect of pH, volume, and the binary system of Cr(III) and Cr(VI) solutions with a starting concentration of 100 mg/L. At pH 8.0, the adsorption of Cr(III) and Cr(VI) was up to 14.13 mg/g± 0.42 mg/g and 1.11 mg/g± 0.36 mg/g, respectively, validating that it is indeed possible to selectively adsorb one valence over another. This is mostly owing to the starch-graft-itaconic acid hydrogel functional groups (e.g., carbonyl, carboxyl), that depending on the pH, can become positively charged, negatively charged, or neutrally charged, contributing to this selectivity. Furthermore, because the stable ionic forms of Cr(III) are similarly pH dependent, the major adsorption mechanisms for Cr(III) by starch-graft-itaconic acid hydrogels may be through electrostatic interactions, ion exchange, and surface complexation.

Performance of Dye Removal from Single and Binary Component Systems by Adsorption on Composite Hydrogel Beads Derived from Fruits Wastes Entrapped in Natural Polymeric Matrix.

The treatment of contaminated water is currently a major concern worldwide. This work was directed towards the preparation of a composite hydrogel by entrapping cherry stones powder on chitosan, which is known as one of the most abundant natural polymers. The synthesized material was characterized by scanning electron microscopy, by Fourier transform infrared spectroscopy, and by the point of zero charge determination. Its ability to remove two azo dyes models (Acid Red 66 and Reactive Black 5) existing in single form and in binary mixture was evaluated. Response Surface Methodology-Central Composite Design was used to optimize three parameters affecting the process while targeting the lowest final contaminant concentrations. The best results were obtained at pH 2, an adsorbent dose of 100 g/L, and a temperature of 30 °C, when more than 90% of the pollutants from the single component systems and more than 70% of those of the binary mixtures were removed from their aqueous solutions. The adsorption process was in accordance with Elovich and pseudo-second-order kinetic models, and closely followed the Freundlich and Temkin equilibrium isotherms. The obtained results led to the conclusion that the prepared hydrogel composite possesses the ability to successfully retain the target molecules and that it can be considered as a viable adsorbent material.

Adsorption of Oxytetracycline Hydrochloride and Chloramphenicol in Single and Binary Component Systems by Loofah Sponge-Based Biochar

Adsorption of Oxytetracycline Hydrochloride and Chloramphenicol in Single and Binary Component Systems by Loofah Sponge-Based Biochar

Organo-Vermiculites Modified by Aza-Containing Gemini Surfactants: Efficient Uptake of 2-Naphthol and Bromophenol Blue.

To explore the effect of spacer structure on the adsorption capability of organo-vermiculites (organo-Vts), a series of aza-containing gemini surfactants (5N, 7N and 8N) are applied to modify Na-vermiculite (Na-Vt). Large interlayer spacing, strong binding strength and high modifier availability are observed in organo-Vts, which endow them with superiority for the adsorption of 2-naphthol (2-NP) and bromophenol blue (BPB). The maximum adsorption capacities of 5N-Vt, 7N-Vt and 8N-Vt toward 2-NP/BPB are 142.08/364.49, 156.61/372.65 and 146.50/287.90 mg/g, respectively, with the adsorption processes well fit by the PSO model and Freundlich isotherm. The quicker adsorption equilibrium of 2-NP than BPB is due to the easier diffusion of smaller 2-NP molecules into the interlayer space of organo-Vts. Moreover, stable regeneration of 7N-Vt is verified, with feasibility in the binary-component system that is demonstrated. A combination of theoretical simulation and characterization is conducted to reveal the adsorption mechanism; the adsorption processes are mainly through partition processes, electrostatic interaction and functional interactions, in which the spacer structure affects the interlayer environment and adsorptive site distribution, whereas the adsorbate structure plays a role in the diffusion process and secondary intermolecular interactions. The results of this study demonstrate the versatile applicability of aza-based organo-Vts targeted at the removal of phenols and dyes as well as provide theoretical guidance for the structural optimization and mechanistic exploration of organo-Vt adsorbents.

Capturing of inorganic and organic pollutants simultaneously from complex wastewater using recyclable magnetically chitosan functionalized with EDTA adsorbent

Herein, we synthesized new and versatile magnetite-doped chitosan−ethylenediaminetetraacetic acid (Fe3O4@CS−EDTA) composite for simultaneous capturing of multiple heavy metal ions: Hg2+, Cd2+, and Ni2+, and methyl orange (MO) dye from complex wastewater through adsorption process. We believe that EDTA in the synthesized adsorbent works as a cross-linker as well as a chelating agent for the capturing of heavy metal ions, while the protonated amino groups of CS capture MO through electrostatic interaction. In the monocomponent system, the adsorption followed to Langmuir model and gave the maximum adsorption capacities of 232.70 ± 14.30, 121.40 ± 7.0, 56.50 ± 2.20, and 732.10 ± 72.40 mg g−1 for Hg2+, Cd2+, Ni2+, and MO, respectively. Kinetics data well fitted to the pseudo-second order (PSO) models, confirmed the chemisorption process. Interestingly, in the case of the binary component system containing both metals and MO, the adsorption capacity of the adsorbent for the dye was not affected by metal presence, while the adsorption of metal ions was enhanced with increasing MO concentration. The adsorption mechanism was confirmed by elemental mapping, XPS and FTIR. Moreover, no significant loss in the adsorption efficiency even after the six continuous adsorption-desorption cycles confirms the great stability and potential of the adsorbent in treating the complex wastewater.

Efficient recovery of aromatic compounds from the wastewater of styrene monomer and propylene oxide co-production plant via hypercrosslinked aryl-rich starch-β-cyclodextrin polymeric sorbent

• A hydrophilic HSPS-ACD(H) with high porosity was fabricated. • HSPS-ACD(H) is a new benchmark sorbent for uptake of AP and 1-PE. • Competitive or synergetic adsorption of co-existing aromatics was studied. • Efficient recovery of the target aromatics was demonstrated in fixed bed column. • DFT calculations provided insights into mechanism for selective adsorption. Adsorptive recovery of valuable components from industrial wastewater is highly desirable for avoiding resource wastage but remains a challenge. Herein, we develop an efficient continuous adsorption process for recovering aromatic compounds in wastewater from styrene monomer and propylene oxide co-production (SMPO) plant. Based on our insight into the potential of bio-based porous materials for adsorption application, starch-graft-polystyrene (SPS) and aryl-modified β-cyclodextrin (ACD) were prepared, and novel hypercrosslinked porous polymers combined SPS with ACD (HSPS-ACDs) were synthesized through external crosslinking approach. In a binary-component system, the best-performing one HSPS-ACD(H) with high ACD content and large specific surface area possessed superior capacities for the representative aromatic compounds, acetophenone (AP, 2.81 mmol·g −1 ) and 1-phenylethanol (1-PE, 1.35 mmol·g −1 ) compared with the previously reported materials. Further, the adsorption properties of aromatic compounds on HSPS-ACD(H) were investigated in batch mode. For practical application, continuous adsorption experiments were conducted in a HSPS-ACD(H)-packed fixed bed, where the target aromatic components in wastewater were effectively retained and further released by elution. Besides showing the reversible adsorption and efficient enrichment effect, the HSPS-ACD(H)-packed fixed bed also maintained great stability in multiple cycles. Moreover, quantum chemical calculations were performed to elucidate the potential mechanism of adsorption of AP and 1-PE onto HSPS-ACD(H).

Rational fabrication of cadmium-sulfide/graphitic-carbon-nitride/hematite photocatalyst with type II and Z-scheme tandem heterojunctions to promote photocatalytic carbon dioxide reduction

Artificial photosynthesis has become one of the most attractive strategies for lowering atmospheric carbon dioxide (CO2) level and achieving the carbon balance; whereas, the fast electron–hole recombination and sluggish charge transfer in photocatalysts are themain stumbling blocks to the applications. Constructing semiconductor nano-heterostructures provides a promising strategy to accelerate the separation and transfer of photoinduced charge carriers for promoting the multielectron CO2 reduction reaction. Herein, a CdS/g-C3N4/α-Fe2O3 three-component photocatalyst consisting of type II and Z-scheme tandem heterojunctions is skillfully fabricated via the solvothermal synthesis followed with photoinduced deposition. The CdS/g-C3N4/α-Fe2O3 tandem-heterojunction photocatalyst exhibits superior performance toward the conversion of CO2 to fuels (CO and CH4), compared with the single- and binary-component systems, owing to the favorable energy-level alignment, accelerated charge separation, facilitated water dissociation and sufficient reactive-hydrogen provision. The total consumed electron number of CdS/g-C3N4/α-Fe2O3 catalyst for CO2 reduction is about 10.5 times that of pure g-C3N4. The photocatalytic mechanism is elucidated according to detailed characterizations and in-situ spectroscopy analyses. This work sheds light on the rational construction of heterojunction photocatalysts to promote the conversion of CO2 to solar fuels, without using any sacrifice reagent or noble-metal cocatalysts.

The enrichment and detection of mercury ions in fluorescent hydrogels

<p indent="0mm">Mercury ions are easily converted into methylmercury, which is easy to accumulate in the body under the action of microorganisms and eventually cause damage to the human body. Therefore, the development of heterogeneous sensors for the enrichment and detection of mercury ion in wastewater is urgently required. In this paper, a fluorescent hydrogel integrating enrichment and detection is prepared by self-assembly combining hydrothermally synthesized nitrogen-sulfur-carbon dots with a hydrogel. The fluorescent hydrogel (AAH) is well characterized by scanning electron microscopy (SEM), Fourier Transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM), <italic>etc</italic>. The effects of solution pH, temperature, reaction time, and the Hg²⁺ enrichment ability in binary component system were investigated with static batch experiments on AAH. The porous structure and abundant chemical groups of AAH show excellent enrichment ability for mercury ions with the maximum adsorption capacity of <sc>606.06 mg/g.</sc> In addition, the detection of Hg²⁺ by AAH is estimated by fluorescence analyses, which proves the sensitive fluorescence response and high selectivity to mercury ions. The results imply that AAH has great potential in environmental applications of mercury ion enrichment and monitoring.

Multi-hydroxyl containing organo-vermiculites for enhanced adsorption of coexisting methyl blue and Pb(II) and their adsorption mechanisms

To address the competitive adsorption of complex wastewater components on organo-vermiculites (organo-Vts), multi-hydroxy containing gemini surfactants varying in alkyl chain length (G12, G14 and G16) are designed and applied for modifying Na-vermiculite (Na-Vt) targeted to the removal of co-existing MB and Pb(II). Organo-Vts exhibit enhanced hydrophobicity and enlarged interlayer spacing compared with Na-Vt, with the saturated modifier dosage reaching as low as 0.4 CEC of Na-Vt. Shorter alkyl chain induces suitable packing density and interlayer environment, endowing G12-Vt the highest adsorption capacity towards MB/Pb(II) compared with G14-Vt and G16-Vt (178.3/63.0 mg/g compared with 143.7/38.1 and 88.6/36.6 mg/g, respectively). Freundlich isotherm and PSO kinetic model are agreeable (the values of R2 are higher than 0.98) with the endothermic adsorption processes. Notably, a simultaneous effect in binary-component system is obtained, and the maximum adsorption capacities of G12-Vt towards MB/Pb(II) reaching 349.9 and 124.5 mg/g, which are 1.96 and 1.95 times higher than single-component system, respectively. Combination of theoretical fitting and molecular simulation co-reveals the adsorption mechanism: the simultaneous effect is due to the providing of additional active sites by the adsorbed MB, which is stronger than that between Pb(II) and the modifier. Existence of π-ion interaction enhances the retention of Pb(II) for a further step. This work broadens a new research perspective for complex wastewater treatment and provides a deep understanding of the stimulative adsorption mechanism between dyes and metal ions.