Higher Adsorption Capacity For Cu Research Articles

Properties of Biochar Prepared by Solar Pyrolysis and Its Adsorption of Cu<sup>2+</sup> in Water

This study investigates the potential of biochar produced via a solar pyrolysis system and its effectiveness in removing copper (Cu<sup>2+</sup>) ions from water, presenting a sustainable and energy-efficient method for biochar production and biomass recycling. Two common agricultural and livestock wastes, corn straw and cow dung, were used as raw materials to produce biochar. These materials underwent solar pyrolysis under limited oxygen conditions to produce biochar, which was then compared to biochar produced via traditional pyrolysis. The comparison involved elemental analyses, infrared spectroscopy, scanning electron microscopy, and specific surface area and pore size analysis to highlight differences in their physical and chemical properties. Adsorption experiments were conducted to evaluate the adsorptive capacity of biochar for copper ions (Cu<sup>2+</sup>) from water, determining the optimal pH conditions and underlying adsorption mechanisms. The findings reveal that biochar produced through solar pyrolysis exhibits similar properties and Cu<sup>2+</sup> adsorption capacities to those prepared by traditional methods. Specifically, cow dung biochar demonstrated a higher adsorption capacity for Cu<sup>2+</sup> compared to corn straw biochar. The Cu<sup>2+</sup> adsorption by corn straw biochar followed the Langmuir isothermal adsorption model and pseudo-second-order kinetic equation, whereas cow dung biochar conformed to the Freundlich isothermal adsorption model and pseudo-second-order kinetic equation. By demonstrating the comparable efficacy of solar pyrolysis biochar in heavy metal adsorption, this study highlights its potential for sustainable environmental remediation and biomass utilization.

Synergistic and antagonistic adsorption mechanisms of copper(II) and cefazolin onto bio-based chitosan/humic composite: A combined experimental and theoretical study

In this study, a bio-based chitosan adsorbent modified by humic was synthesized. The adsorbent exhibited amphoteric adsorption properties and had a higher adsorption capacity for Cu(II) and cefazolin (CEF) than its precursors. The impacts of pH on the speciation and adsorption of Cu(II) and CEF were analyzed. The synergistic and antagonistic adsorption in Cu(II)/CEF co-existing system were systematically investigated. The adsorption amount of CEF significantly increased by 84 %, owing to the bridge effect of Cu(II). While the uptake of Cu(II) decreased by 29 % at CEF concentration of 0.3 mmol/L, due to the formation of organic ligand complex between Cu(II) and CEF with low affinity to the adsorbent. The adsorption mechanisms of Cu(II) and CEF were analyzed by XPS and Density functional theory (DFT). Through DFT calculations, the interaction configurations of Cu(II) and CEF on adsorbent as well as Cu(II)-CEF complexes were configurated. The possible Cu(II)-CEF complexes configuration were optimized, and the complex configuration (Cu-N2/O1/O2) was the most stable combination structure with the lowest binding energy (−2066.61 kJ/mol). Interaction region indicator (IRI) model further elucidated the chemical and weak interactions between CEF and Cu(II) in coexisting system. In addition, the influence of common inorganic electrolytes on the adsorption of Cu(II) and CEF was assessed. The adsorbent could be stably recycled for five cycles with little loss, indicating the potential application in the treatment of combined pollution. This study proposed more insights into the interactions of heavy metal ions and antibiotics in the coexistence system onto the adsorbents containing amine and carboxyl groups.

Adsorption of Cu(II) and Ni(II) from Aqueous Solutions Using Synthesized Alkali-Activated Foamed Zeolite Adsorbent: Isotherm, Kinetic, and Regeneration Study.

Water pollution, particularly from heavy metals, poses a significant threat to global health, necessitating efficient and environmentally friendly removal methods. This study introduces novel zeolite-based adsorbents, specifically alkali-activated foamed zeolite (AAFZ), for the effective adsorption of Cu(II) and Ni(II) ions from aqueous solutions. The adsorbents' capabilities were comprehensively characterized through kinetic and isotherm analyses. Alkaline activation induced changes in chemical composition and crystalline structure, as observed via XRF and XRD analyses. AAFZ exhibited a significantly larger pore volume (1.29 times), higher Si/Al ratio (1.15 times), and lower crystallinity compared to ZZ50, thus demonstrating substantially higher adsorption capacity for Cu(II) and Ni(II) compared to ZZ50. The maximum monolayer adsorption capacities of ZZ50 and AAFZ for Cu(II) were determined to be 69.28 mg/g and 99.54 mg/g, respectively. In the case of Ni(II), the maximum monolayer adsorption capacities for ZZ50 and AAFZ were observed at 48.53 mg/g and 88.99 mg/g, respectively. For both adsorbents, the optimum pH for adsorption of Cu(II) and Ni(II) was found to be 5 and 6, respectively. Equilibrium was reached around 120 min, and the pseudo-second-order kinetics accurately depicted the chemisorption process. The Langmuir isotherm model effectively described monolayer adsorption for both adsorbents. Furthermore, the regeneration experiment demonstrated that AAFZ could be regenerated for a minimum of two cycles using hydrochloric acid (HCl). These findings highlight the potential of the developed adsorbents as promising tools for effective and practical adsorption applications.

Triggering antibacterial activity of a common plant by biosorption of selected heavy metals.

The presented study proposes an efficient utilization of a common Thymus serpyllum L. (wild thyme) plant as a highly potent biosorbent of Cu(II) and Pb(II) ions and the efficient interaction of the copper-laden plant with two opportunistic bacteria. Apart from biochars that are commonly used for adsorption, here we report the direct use of native plant, which is potentially interesting also for soil remediation. The highest adsorption capacity for Cu(II) and Pb(II) ions (qe = 12.66 and 53.13 mgg-1, respectively) was achieved after 10 and 30 min of adsorption, respectively. Moreover, the Cu-laden plant was shown to be an efficient antibacterial agent against the bacteria Escherichia coli and Staphylococcus aureus, the results being slightly better in the former case. Such an activity is enabled only via the interaction of the adsorbed ions effectively distributed within the biological matrix of the plant with bacterial cells. Thus, the sustainable resource can be used both for the treatment of wastewater and, after an effective embedment of metal ions, for the fight against microbes.

Ball Mill, Humic Acid, and Rock Phosphate-Modified Conocarpus Biochar for Efficient Removal of Heavy Metals from Contaminated Water

An increasing trend of anthropogenic activities such as urbanization and industrialization has resulted in induction and accumulation of various kinds of heavy metals in the environment, which ultimately has disturbed the biogeochemical balance. Therefore, the present study was conducted to probe the efficiency of conocarpus (Conocarpus erectus L.) waste-derived biochar and its modified derivatives for the removal of lead (Pb), cadmium (Cd), copper (Cu), and zinc (Zn) from aqueous solutions. Biochar was produced at 600 °C and modified with humic acid (1:10 w/v ratio) and rock phosphate (0.5:1 w/w ratio). Additionally, produced biochar, as well as humic acid and rock phosphate-modified biochars, were subjected to ball milling separately. Equilibrium and kinetics batch experiments were conducted to investigate heavy metals adsorption on synthesized adsorbents. Adsorption isotherms and kinetics models were employed to explore the adsorption efficiency of produced materials for metals adsorption. Among all the applied adsorbents, ball-milled biochars showed comparatively higher adsorption compared to un-milled biochars. Humic acid and rock phosphate-modified milled biochar showed the highest adsorption capacity for Pb (18.85 mg g−1), while rock phosphate-modified milled biochar showed the highest adsorption capacity for Cu and Zn (24.02 mg g−1 and 187.14 mg g−1), and humic acid modified biochar adsorbed maximum Cd (30.89 mg g−1). Adsorption isotherm study confirmed Freundlich as the best-suited model (R2= 0.99), while kinetics adsorption was well described by the pseudo-second-order (R2 = 0.99). Hence, it was concluded that ball-milled biochar modified with humic acid and rock phosphate could potentially remove heavy metals from contaminated water.

Efficient and Rapid Removal of Pb(II) and Cu(II) Heavy Metals from Aqueous Solutions by MgO Nanorods

In this study, the adsorption capability of MgO nanorods for the quick and effective elimination of Cu(II) and Pb(II) heavy metals from wastewater was examined. The MgO nanorods were produced via simple coprecipitation process. Various characterization techniques were used to investigate the morphological and chemical properties of the as-prepared nanomaterial. Moreover, the influences of initial heavy-metal ion concentration, pH, and contact time were investigated to evaluate the removal efficiency of the nanomaterials. The adsorption process followed pseudo-second order and Langmuir adsorption isotherm models, according to kinetics and isotherm investigations, respectively. MgO nanoparticles exhibited a high adsorption capacity for Cu(II) (234.34 mg/g) and Pb(II) (221.26 mg/g). The existence of interfering ions in the aqueous solution leads to a decrease in the adsorption capacity. Surface complexation was determined as the key contributor to the adsorption of Cu(II) and Pb(II) heavy-metal ions onto MgO nanorods. Notably, regeneration experiments demonstrate the potential applicability of MgO nanorods for the elimination of Pb(II) and Cu(II) from aqueous solution.

Ecofriendly nanoparticles derived from water industry byproducts for effective removal of Cu (II) from wastewater: Adsorption isotherms and kinetics

• Water treatment residuals nanosorbent (nWTR) were characterized and used for copper removal. • The efficient of nWTR was 3.7 times higher than bulk WTR in adsorption copper ions. • nWTR maintained its high adsorption potential (98.7 %)at pH 6. • The adsorption process of copper from wastewater can be repeated for.4 times using the same sorbent(nWTR). Water Treatment Residual nanoparticles (nWTR) has been identified as an adsorbent for the efficient elimination of copper (II) from wastewater. Adsorption parameters pH, dosage, contact time, initial concentration, and temperature were assessed to detect the optimum adsorption conditions for purification contaminated wastewater. The equilibrium between liquid and solid phase occurred rapidly after (120 min) . nWTR was found to have high adsorption capacity for Cu (II). From Langmuir isotherm, the adsorption capacity for Cu (II) was 71.9 mg g −1 , which is about 3.7 times higher than that of bulk particles of WTR. The kinetics data for Cu (II) adsorption followed the pseudo-first-order kinetics. The thermodynamic parameters investigated the spontaneous and endothermic nature of the Cu (II) adsorption activity. High removal percentage (91%) was obtained after five cycles of reusing nWTR indicating the capability of using the sorbent more than four times.

Kinetics and Size Effects on Adsorption of Cu(II), Cr(III), and Pb(II) Onto Polyethylene, Polypropylene, and Polyethylene Terephthalate Microplastic Particles

Due to its small size, large specific surface area and hydrophobicity, microplastics, and the adsorbed contaminants may together cause potential negative effects on ecosystems and human beings. In this study, kinetics and size effects on adsorption of Cu(II), Cr(III), and Pb(II) onto PE, PP and PET microplastic particles were explored. Results indicated that the PE and PET microplastics have the higher adsorption capacity for Cu(II), Cr(III), and Pb(II) than that for PP microplastic. The adsorption capacity was affected by microplastic types and metal species. Among the three metals, Pb(II) had the largest adsorption amount on microplastic particles, especially on PET particles. Moreover, the adsorption capacities of microplastics increase with the decrease of particle size. The metal adsorption capacity of <0.9 mm microplastics is greater than that of 0.9–2 mm and 2–5 mm microplastics. The size effect on metal adsorption was largest for PE microplastic. More attention should be paid in case of the coexistence of heavy metals and tiny PE and PET microplastics in the environment.

A highly efficient adsorbent constructed by the in situ assembly of Zeolitic imidazole framework-67 on 3D aramid nanofiber aerogel scaffold

• ZIF-67 was in situ assembled onto ANF aerogel to get 3D monolith adsorbent. • ANF/ZIF-67 aerogel showed stable and competitive structural features. • ANF/ZIF-67 aerogel demonstrated high adsorption capacity for Cu 2+ and Cr 6+ . • ANF/ZIF-67 aerogel displayed excellent adsorption capacity for CV and MO. • The adsorption capacity maintained up to 80% after five times of usage. The fabrication of a high-efficiency adsorbent, as a promising candidate for removing metal ions and organic dyes from aqueous solution, is a research hotspot but remains challenging. Aramid nanofibers (ANFs) are emerging building blocks that have realized multifunctional applications in various fields because of their intrinsic mechanical and chemical stability. In this research, three-dimensional (3D) ANF aerogel was assembled and applied in for in situ assembly of zeolitic imidazole framework-67 (ZIF-67). The aim, was to fully exploit the structural advantages of this composite’s ultra-low bulk density, large specific surface area, and high porosity, as well as provide more available adsorption sites by ZIF-67 polyhedrons, to facilitate pollutant adsorption from waste water. The prepared 3D ANF/ZIF-67 composite aerogel possessed favorable adsorption performance for heavy metal ions (250.95 and 183.29 mg/g for Cu 2+ and Cr 6+ , respectively) and organic dyes (199.36 and 65.98 mg/g for CV and MO, respectively), greatly exceeding that of the corresponding 3D ANF aerogel. Desorption experiments further demonstrated that up to 80% adsorption performance for heavy metal ions and organic dyes could be maintained after five times of usage. Hence, this research can provide new insights into the preparation of highly efficient adsorbents for water treatment.

Preparation and graft modification of hierarchically porous ferriferrous oxide for heavy metal ions adsorption

Hierarchically porous ferriferrous oxide (Fe3O4) was facilely synthesized via a sol-gel process accompanied by phase separation, and further graft modified by dopamine (DA) and polyamido-amine (PAMAM) to prepare macroporous Fe3O4@DA@PAMAM for heavy metal ions adsorption. Appropriate phase separation inducer (poly(acrylamide), PAA) and solvent allows the formation of iron oxide xerogels with interconnected macropores and cocontinuous skeletons. Two-step heat treatment at 200 °C for 30 min in air and then at 500 °C for 2 h in N2 atmosphere leads to the precipitation of crystalline phase, Fe3O4, with high magnetic properties, without any deterioration of the macrostructure. The macroporous Fe3O4@DA@PAMAM show a core-shell structure and high adsorption capacity for Cu(II), Pb(II), and Cd(II) ions, which are promisingly used for removal of heavy metal ions.

Removal of Cu(II) from Aqueous Solutions Using Amine-Doped Polyacrylonitrile Fibers

Polyacrylonitrile (PAN) fibers were prepared via electrospinning and were modified with diethylenetriamine (DETA) to fabricate surface-modified PAN fibers. The surface-modified PAN fibers were used to evaluate their adsorption capacity for the removal of Cu(II) from aqueous solutions. Batch adsorption experiments were performed to examine the effects of the modification process, initial concentration, initial pH, and adsorbent dose on the adsorption of Cu(II). Kinetic analysis revealed that the experimental data fitted the pseudo-second-order kinetic model better than the pseudo-first-order model. Adsorption equilibrium studies were conducted using the Freundlich and Langmuir isotherm models, and the findings indicated that the PAN fibers modified with 85% DETA presented the highest adsorption capacity for Cu(II) of all analyzed samples. Moreover, the results revealed that the Freundlich model was more appropriate than the Langmuir one for describing the adsorption of Cu(II) onto the modified fibers at various initial Cu(II) concentrations. The maximum adsorption capacity was determined to be 87.77 mg/g at pH 4, and the percent removal of Cu(II) increased as the amount of adsorbent increased. Furthermore, the surface-modified PAN fibers could be easily regenerated using NaOH solution. Therefore, surface-modified PAN fibers could be used as adsorbents for the removal of Cu(II) from aqueous solutions.

Effective removal of copper ions from aqueous solution by iminodiacetic acid-functionalized Paeonia ostii seed coats

A novel and efficient adsorbent, iminodiacetic acid-functionalized Paeonia ostii seed coats (IDA-PSC), was prepared for the removal of copper ions from aqueous solution. Structural and morphological characterizations were performed using BET, SEM, FT-IR and XPS analyses. The influence of solution pH and ionic strength, adsorption kinetics, isotherms and desorption studies were investigated. The results revealed that the IDA-PSC adsorbent presented high adsorption capacity for Cu(II) even at pH values as low as 2, or in the presence of Na+ and Ca2+. Langmuir isotherm and Pseudo-second-order models described the experimental data well. Maximum monolayer adsorption capability was 36.6 mg g−1 at 25 °C. Thermodynamic studies confirmed the spontaneous and endothermic nature of adsorption process. FT-IR and XPS analysis indicated that the N/O-containing functional groups on the surface of IDA-PSC played important roles in the adsorption process of Cu(II). Besides, intraparticle diffusion, electrostatic attraction and ion-exchange could greatly contribute to the Cu(II) adsorption. Lastly, reusability study suggested that the efficiency did not change much even after six consecutive cycles, which further confirmed that the IDA-PSC could be a promising adsorbent for the efficient removal of copper ions from aqueous solution.

Influence of heavy metal sorption pathway on the structure of biogenic birnessite: Insight from the band structure and photostability

Birnessite, primarily formed by biooxidation, is a common semiconducting Mn oxide in nature and a major controller of heavy metals cycling processes. In turn, the heavy metal sorption pathway alters its structural chemistry and thus the electronic structure. We synthesize three kinds of birnessite, namely biogenic (bio-birnessite), Cu coprecipitated (co-birnessite) and Cu adsorbed birnessite (ad-birnessite), to investigate the influence of Cu(II) occupancy on the structure, semiconducting property and photostability of birnessite. XRD show co-birnessite holds the same hexagonal symmetry as bio-birnessite, whereas ad-birnessite transforms to triclinic symmetry as reflected by the splitting reflections at 2.44 and 1.42 Å. The adsorption process is accompanied by a more intense releasing of Mn(II) (156.88 μM/L) from a bio-birnessite analog δ-MnO2 in light than in dark (19.55 μM/L), suggesting the photoreductive releasing of Mn(II) promotes structure transformation. Conformably, both the Mn average oxidation state (AOS) (3.32) and mole ratio of Cu/Mn (0.08) in ad-birnessite is lower than those in co-birnessite (AOS: 3.47, Cu/Mn ratio: 0.17). EXAFS demonstrate different Cu complexing features in ad- and co-birnessite that the ratio of Cu incorporated (INC) into vacancies is 1.16 and 0.45 for ad- and co-birnessite, respectively. UV–vis diffuse reflection spectra (DRS) and photoelectron spectrometer (PS) exhibit the band gap (Eg) and valence band (VB) of bio-birnessite are 2.05 and −5.58 eV, while there is 0.1 and 0.05 eV decrease of Eg, and 0.08 and 0.16 eV lowering of VB in co- and ad-birnessite, respectively. The reduced Eg guarantee them to generate photoelectron-hole pairs under mild indoor visible light, and the lower energy level of VB in ad-birnessite makes its VB holes more reactive to accept electrons from electron donors. Further density functional theory (DFT) calculations focus on interpreting the fine structures brought by different Cu sorption pathways on the electronic structure of birnessite. A Mn vacancy in a 2 × 2 × 1 hexagonal birnessite cell significantly reduces Eg from 1.60 to 0.28 eV by hybridizing Mn 3d and O 2p states in VB. The doped Cu reduces Eg mainly through incorporating Cu 3d orbital in VB. The INC Cu in hexagonal birnessite contributes more to reduce Eg (1.60–0.34 eV) than TCS Cu (1.60–1.20 eV), while in triclinic birnessite cell, TCS Cu causes more obvious reduction of Eg (1.68–0.28 eV) than INC Cu (1.68–1.55 eV). Thus, we conclude the vacancy imposes more effect on the electronic structure of hexagonal co-birnessite than doped Cu in TCS or INC sites; and the band structure of co-birnessite is more sensitive to INC Cu, in contrast to TCS Cu affecting more in ad-birnessite. Overall, the crystal structure differs according to Cu fixation pathway, which imposes a comprehensive effect on band structure and photostability contributed by vacancies, Cu occupancy sites and structural symmetry. Cu coprecipitating with birnessite is suggested as a preferred method in practical clean-up of metals such as Cu, due to the higher adsorption capacity for Cu, better stability of TCS Cu and better photostability influenced by Cu.

Fabrication of Fe3O4@polydopamine@polyamidoamine core–shell nanocomposites and their application for Cu(ii) adsorption

Fe3O4@PDA@PAMAM nanocomposites were fabricated with a polydopamine assisted method, possessing excellent magnetic properties and high adsorption capacity for Cu(ii).

Synthesis and characterization of magnetic amidoximated chitosan-g poly(polyacrylonitrile)/laponite RD nanocomposites with enhanced adsorption capacity for Cu$^{2+}$

Magnetic amidoximated nanocomposites based on a combination of chitosan and magnetic laponite RD were prepared and examined for the removal of Cu$^{2+}$ from aqueous solutions. Magnetic laponite RD was prepared by an in situ method. In order to prepare magnetic amidoximated nanocomposites, acrylonitrile was grafted to chitosan in the presence of magnetic laponite RD. Then the nitrile pendants on magnetic chitosan-g-polyacrylonitrile/laponite RD (mChtioPANLap) were converted to amidoxime groups. We developed a polyamidoximated magnetic nanocomposite based on a mixture of chitosan/laponite RD, possessing a high adsorption capacity for Cu$^{2+}$. By introducing magnetic laponite RD the adsorption capacity of nanocomposites for Cu$^{2+}$ was significantly improved. The effects of contact time, initial concentration of Cu$^{2+}$, initial pH of Cu$^{2+}$ solutions, and temperature on adsorption process were investigated. Studying adsorption kinetics showed that the experimental data are described better by the pseudo-second-order kinetic model. The adsorption of Cu$^{2+}$ on nanocomposites followed the Langmuir isotherm model well. Additionally, the fitting of isotherm data by the Dubinin-Radushkevich model showed that the adsorption process occurred by physisorption mechanism. The thermodynamic data indicated that the adsorption process was spontaneous and endothermic.

Preparation and evaluation of adipic acid dihydrazide cross-linked carboxymethyl chitosan microspheres for copper ion adsorption

Abstract Adipic acid dihydrazide (ADH) was used to cross-link carboxymethyl chitosan (CMCS) microspheres for Cu 2+ removal from aqueous solution. SEM, FTIR, XPS and BET techniques were performed to characterize the ADH cross-linked CMCS (ADH-CMCS) microspheres. The effects on adsorption capacities of pH value, adsorption time, and initial Cu 2+ concentration were investigated. The adsorption experiments demonstrated ADH-CMCS microspheres had high adsorption capacity for Cu 2+ removal. Furthermore, in order to investigate the effect of ADH in ADH-CMCS microspheres on Cu 2+ adsorption, cross-linking experiments and XPS tests were carried out to reveal the adsorption mechanism. The results suggested that ADH in ADH-CMCS microspheres had a compensation action on its consumption of binding sites for Cu 2+ adsorption. The XPS etching results showed cross-linking reaction occurred mainly on the surfaces of the microspheres. The kinetics of Cu 2+ adsorption on ADH-CMCS microspheres complied with the pseudo-second-order model, indicating a chemical reaction process. The adsorption data analysis using three different adsorption isotherm models indicated that ADH-CMCS microspheres were of heterogeneity surfaces. Moreover, the ADH-CMCS microspheres still exhibited good adsorption performances after the fifth adsorption-desorption cycle.

The application of prepared porous carbon materials: Effect of different components on the heavy metal adsorption.

In this study, five typical municipal solid waste (MSW) components (tyres, cardboard, polyvinyl chloride (PVC), acrylic textile, toilet paper) were used as raw materials to prepare four kinds of MSW-based carbon materials (paperboard-based carbon materials (AC1); the tyres and paperboard-based carbon materials (AC2); the tyres, paperboard and PVC-based carbon materials (AC3); the tyres, paperboard, toilet paper, PVC and acrylic textile-based carbon materials (AC4)) by the KOH activation method. The characteristic results illustrate that the prepared carbon adsorbents exhibited a large pore volume, high surface area and sufficient oxygen functional groups. Furthermore, the application of AC1, AC2, AC3, AC4 on different heavy metal (Cu(2+), Zn(2+), Pb(2+), Cr(3+)) removals was explored to investigate their adsorption properties. The effects of reaction time, pH, temperature and adsorbent dosage on the adsorption capability of heavy metals were investigated. Comparisons of heavy metal adsorption on carbon of different components were carried out. Among the four samples, AC1 exhibits the highest adsorption capacity for Cu(2+); the highest adsorption capacities of Pb(2+) and Zn(2+) are obtained for AC2; that of Cr(3+) are obtained for AC4. In addition, the carbon materials exhibit better adsorption capability of Cu(2+) and Pb(2+) than the other two kind of metal ions (Zn(2+) and Cr(3+)).

Melamine-based microporous polymer for highly efficient removal of copper(II) from aqueous solution

In this study, we investigated the ability of a melamine-based microporous polymer network as an adsorbent for removal of copper(II) species from aqueous solutions. A designed Schiff based network (SNW) with high specific surface area was synthesized using melamine and terephthalaldehyde monomers at 180 °C for 3 days followed by a freeze-drying process. The porous structure of the material was confirmed by SEM analysis and CO2 adsorption/desorption studies at 77.3 K. The adsorption character of the SNW polymer for various metal salts, namely Pb(II), Fe(II), Hg(II), Zn(II), Ni(II) and Cd(II), was investigated and a specific sorption behaviour against Cu(II) salts was observed. The role of pH and contact time was examined and the highest adsorption capacity for Cu(II) was found as 92% with pH 3.5 at the end of 300 min. As evidenced by XRD and Fourier transform infrared spectral analysis, the sorption mechanism is attributed to the coordination system formed between amino groups in the porous structure and Cu(II) ions. Reusability of the system was also demonstrated by applying four cycles without any significant loss of activity. © 2016 Society of Chemical Industry

Adsorption of copper(II) ions by a chitosan–oxalate complex biosorbent

Oxalic acid, an effective metal-chelating ligand, is abundant in natural resources. In this study, a chitosan–oxalate complex biosorbent (COCB) was prepared by an iontropic cross-linking method. The COCB beads were characterized by Fourier transform infrared (FT-IR) spectra, X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The XRD analysis shows that Cu(II) ions can form complexes with chitosan and oxalate. Adsorption of Cu(II) ions onto COCB beads was pH-dependent. The isothermal adsorption data fitted well to Langmuir equation with the maximum adsorption capacities of 227.27mg/g for porous COCB beads and 175.44mg/g for non-porous COCB beads at pH 5.0. The adsorption kinetics described by the pseudo-second-order diffusion models, suggesting that the rate-limiting step in adsorption was chemical sorption. Thermodynamic parameters (ΔG°<0 and ΔH°>0) indicated a spontaneous and endothermic adsorption process. The COCB bioadsorbent exhibited fast adsorption rate and high adsorption capacity for Cu(II) uptake.

Constituting fully integrated visual analysis system for Cu(II) on TiO₂/cellulose paper.

As a cheap and abundant porous material, cellulose filter paper was used to immobilize nano-TiO2 and denoted as TiO2/cellulose paper (TCP). With high adsorption capacity for Cu(II) (more than 1.65 mg), TCP was used as an adsorbent, photocatalyst, and colorimetric sensor at the same time. Under the optimum adsorption conditions, i.e., pH 6.5 and 25 °C, the adsorption ratio of Cu(II) was higher than 96.1%. Humic substances from the matrix could be enriched onto TCP but the interference of their colors on colorimetric detection could be eliminated by the photodegradation. In the presence of hydroxylamine, neocuproine, as a selective indicator, was added onto TCP, and a visual color change from white to orange was generated. The concentration of Cu(II) was quantified by the color intensity images using image processing software. This fully integrated visual analysis system was successfully applied for the detection of Cu(II) in 10.0 L of drinking water and seawater with a preconcentration factor of 10(4). The log-linear calibration curve for Cu(II) was in the range of 0.5-50.0 μg L(-1) with a determination coefficient (R(2)) of 0.985 and its detection limit was 0.073 μg L(-1).