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Surface functionalized biomass for adsorption and recovery of gold from electronic scrap and refinery wastewater
Abstract and Figures
In this study, polyethylenimine (PEI) modified Lagerstroemia speciosa leaves powder (PEI-LS) as low-cost and eco-friendly biosorbent was efficiently applied for gold recovery from acidic solution. Our experimental data show that PEI-LS is effective in complete recovery of gold at pH 1, compared to the raw L. speciosa leaves powder (raw LS) biomass. The adsorption kinetic results show gold adsorption reaches equilibrium in 6 h and follows a pseudo-second order kinetic. The adsorption isotherm data were best explained by Freundlich model and the monolayer adsorption capacity of PEI-LS for gold are in the range 286–313 mg/g. Thermodynamic parameters suggest that gold adsorption on PEI-LS was spontaneous and endothermic in nature. The developed PEI-LS was reusable up to 4 cycles with ~98 % gold recovery. Further, the calculated separation factor values suggest the PEI-LS shows high selectivity for low concentration of gold over the other co-existing metal ions in binary mixtures. Various instrumental characterization of raw LS and PEI-LS confirms the successful grafting of PEI on biomass surface. Surface analytical techniques like X-ray photoelectron spectroscopic (XPS) analysis confirms the adsorption-reduction mechanism of gold ions on PEI-LS leading to the formation of zero-valent gold on the biosorbent surface. The XPS was also used to characterize the PEI-LS surface functional groups (N1s) responsible for gold adsorption-reduction mechanism. The PEI-LS was successfully applied for quantitative gold recovery (≥95 %) from an acidic solution of electronic scrap, gold refining sludge, and wastewater.
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... One of the most important advantages of using biological waste for gold recovery is that they are easily available in large quantities at low cost. Environmental compatibility, degradability, and renewability are other advantages of them [8][9][10][11][12][13][14][15][16][17][18]. ...
... Te value of (1/n) less than 1 implies a desirable adsorption of Au (III) onto GA. Te dimensionless parameter (R L ) indicates the nature of adsorption with R L � 0 indicating the irreversible adsorption process, R L > 1 showing an undesirable adsorption process, 0 < R L < 1 demonstrating a desirable adsorption process, and RL � 1 representing a linear process [17,55,64,71,80,81]. Te obtained value for R L (0.421-0.814) was less than one, indicating that the adsorption process was desirable. ...
A low-cost new green adsorbent (GA) was synthesized by tannin-rich pomegranate peel powder and formaldehyde for the fast and selective recovery of Au (III). It was characterized by Fourier transform infrared spectroscopy (FT-IR), Brunauer–Emmett–Teller (BET), elemental analysis (CHN), field emission scanning electron microscopy (FE-SEM), and energy-dispersive X-ray spectroscopy (EDS) (FE-SEM-EDS-mapping). The optimal values of influential factors were defined using a central composite design based on the response surface methodology (CCD-RSM). Adsorption properties were investigated by the kinetic, isotherm, thermodynamic, and interference of coexisting metal ions at optimum conditions. The experimental adsorption percentage with three repetitions under the optimized conditions such as pH = 2, adsorbent mass = 23 mg, Au (III) concentration = 32 m g L − 1 , and contact time = 30 min was 97% and the highest adsorption capacity of the GA was 315.450 m g g − 1 . The adsorption isotherm and kinetic were clarified by the Freundlich (R2 = 0.952) and pseudo-second-order (R2 = 0.998) models. The thermodynamic study (∆S° > 0, ∆H° > 0, and ∆G° < 0) revealed that Au (III) adsorption via GA was a facile, endothermic, and spontaneous process. The adsorption mechanism could be an electrostatic interaction and reductive adsorption. A small amount of GA (23 mg) adsorbed gold selectively and rapidly (30 min) from coexisting metals present in the waste printed circuit board (PCB) such as Ag, Al, Si, Zn, Pb, Ba, Ni, Ca, Mo, Co, Cr, Mn, Cu, Mg, Fe, and W. These results confirm the use of low-cost and high-efficiency GA to fast and selectively recover gold from waste PCBs.
... Many of the studies are focusing on replacing common adsorbents with biomaterials, because these are lower cost and in addition to being friendly to the environment, they can be modified more easily; [7,8,9,6]. some biomaterials have even come to have better adsorbent capacities than the usual materials [10,11,12,6]. In retention processes, more attention has been focused on metal ion recovery and reuse methods. ...
... Temperature did not show a significant effect on the synthesis if it does not exceed 87 C to avoid the start of the degradation of the organic compounds present in the natural extract. Optimal conditions allowed to obtain a synthesis yield of 98.99% to iron nanoparticle, results that are similar to those expressed by Galeas et al., 2017 who reported yields of 94% and exceed the results expressed by Robles et al., 2019 whose synthesis yields reached a maximum of 35.03% [10,37,38]. ...
Artisanal mining is the main source of mercury emissions in South America, which generates a serious environmental impact due to this toxic metal, recent research is directed to minimize the impact, therefore this study focuses on the green synthesis of nanoparticles for the absorption of mercury in water. For the synthesis of iron nanoparticles, an extract of Eucalyptus grandis was used with iron chloride salts using water as solvent. The synthesized nanoparticles showed a specific surface area of 131.90 m²/g, determined by Brunauer-Emmett-Teller isotherm (BET). Nanoparticles were characterized by Fourier transformed infrared spectroscopy (FTIR) and transmission electron microscopy (MET). The behavior of nanoparticles synthesized during Hg (II) retention was evaluated measuring pH, temperature, nanoparticle dosing, presence of other ions and comparing with other adsorbents. All analyses measured by atomic absorption spectroscopy by the cold vapor technique (CVAAS), presenting a retention percentage for Hg (II) between 75.05 and 79.59% with pH between 4 and 7. The adsorption isothermal was adjusted to the Freundlich model and the percentage of retention of Hg by the synthesized nanoparticle was 79.26%. This work shows a method for obtaining an environmentally friendly mercury adsorbent from iron and E. grandis with a mercury retention capacity comparable to commercial adsorbents.
... 1 t Cellulose occurs spontaneously, and ΔH ϴ and ΔS ϴ represent enthalpy and entropy changes, respectively. The above thermodynamic parameters can be obtained after analyzing the adsorption isotherm (Choudhary et al. 2018). ...
Developing high value-added utilization of waste cotton provides a promising approach for the sustainable development. Herein, the carboxylated cellulose aerogels (CCAs) featuring in micro/nanostructure and directional channel are fabricated from cotton fabrics via the ingenious combination of selective oxidation, high-speed cutting, and freeze-drying. The as-prepared 2.0-CCA demonstrates not only excellent adsorption capacity for cationic dyes in water but also recyclability due to the abundant carboxyl groups (3.20 mmol/g) and the robust porous structure. And it shows a static maximum adsorption capacity (qm) of 751 mg/g and a dynamic breakthrough amount more than 700 mg/g for methylene blue (MB), more efficient than most reported cellulose-based adsorbents. In addition, the 2.0-CCA shows a high equilibrium adsorption capacity (qe) about 680 mg/g for MB at pH = 6 and keeps qe above 600 mg/g even in a broad pH range of 3‒10, indicating a high tolerance to the solution pH value. At an ion concentration lower than 0.25 mol/L, the additional cations such as Na⁺ and K⁺ or anions such as Cl‒, SO42‒, and NO3‒ show a little effect on the qe (higher than 500 mg/g) of 2.0-CCA for MB. The treated dye wastewater can be recycled for fabric dyeing, and there is no significant color difference (∆E) between fabrics dyed with dye liquors prepared with fresh or recycled water. The theoretical study confirms the importance of the electrostatic attraction between carboxyl groups of 2.0-CCA and dye molecules for the efficient adsorption.
... Polyethyleneimine (PEI), a cost-effective polymer with various primary, secondary, and tertiary amine groups, has shown promise in metal ion separation. The addition of PEI to adsorbents increases the binding sites on their surface and addresses the challenge of difficult recovery from water [25][26][27][28][29]. PEI cross-linked with 2,4,6-trichloro-1,3,5-triazine (TCT) enhances metal chloride anion adsorption due to increased N atoms and rigid rings [30,31]. ...
The recovery of Au(III) from solution using adsorbents in the form of granules or powders is challenging due to issues such as instability during the recovery process or mass loss caused by small particle size. This study introduces a PEI-TCT/PVDF composite membrane designed to intercept and capture Au(III) in wastewater. Experimental results demonstrated that the PEI-TCT/PVDF membrane exhibits a broad pH range (1–8) and a high retention efficiency for Au(III) of 97.8%, with a maximum adsorption capacity of 294.5 mg/g. The mechanism of Au(III) adsorption on the PEI-TCT/PVDF membrane was mainly through electrostatic adsorption, which caused AuCl4− to aggregate on the surface of the membrane and gradually reduced to Au0 and Au+. Furthermore, the membrane can be entirely regenerated within 20 min and maintains its performance in subsequent adsorption cycles. This study highlights the potential of PEI-TCT/PVDF membranes for the recovery of precious Au(III).
... range from 0.1 to 1.5 M, with HCl fixed at 1 M, as shown in Table 3. 24 With the best result obtained in the previous step, the effect of the stripping contact time was evaluated using times ranging from 3 to other chemical elements such as palladium, silver, and iron may also be present in PCB pins. 29 In the present study, these elements were not detected by the EDS analysis, probably due to their low concentrations in the samples tested. ...
Advances in technological development mean that the recovery of rare and strategic metals from secondary sources has become essential, due to the high demand for these metals in the production of electronic equipment. Contributing to this goal, the main purpose of this work was to develop Nylon 6 nanofibers modified with the Cyanex 272 organic extractant, for use in the selective recovery of gold present in printed circuit boards from armored vehicles. The nanofibers were produced by the centrifugation technique, employing the Forcespinning® system. The best extraction conditions for the separation and concentration of gold were 10% Cyanex 272, fixed pH of 1.5, contact time of 15 min, and solid:liquid ratio (S/L) of 1/700. Gold extraction efficiencies above 77% were achieved in this step. In the stripping step, efficiencies exceeding 85% were obtained using 1 M HCl, 1 M thiourea, S/L of 1/50, and contact time of 3 min. The nanofibers were evaluated in terms of their adsorption capacity, stability, and capacity for reuse in successive cycles. The results showed that the Nylon 6/Cyanex 272 nanofibers could be used in several extraction and stripping cycles. These nanofibers provided high selectivity in the recovery of gold when applied using real leachate solutions, in the presence of other metals (lead, tin, zinc, and copper). The use of nanofibers modified with Cyanex 272 was shown to be an effective option for gold recovery, with lower environmental impacts, compared to conventional liquid–liquid extraction methods that require the use of organic solvents.
... Diverse sources of cellulose, Lagerstroemia speciosa leaves [36] , coffee grounds [37] , and cotton [38] , with the help of GA, cellulose can be thoroughly mixed with PEI and cross-linked [ 39 , 40 ]. It can also be prepared by dissolving in NaOH/urea/water system, prepared as hydrogel beads, and then reacted with PEI [41] . ...
The removal and enrichment of pollutants in industrial wastewater using efficient adsorption processes have been a hot scientific topic in the field of environmental chemistry and green chemistry. Compared with the progress in the design, synthesis, and performance of polyethyleneimine-modified adsorbent materials at home and abroad, there are few reviews on how to modify polyethyleneimine (PEI) in adsorbent materials through functional group reactions. Therefore, this review attempts to provide a systematic review of how PEI can prepare adsorbent materials by functional group reaction and the adsorption mechanism of inorganic metal ions, phosphates, and dyes in wastewater by PEI. On this basis, future research directions of adsorbent materials are prepared by PEI prospects.
... The results indicated that nitrogen-containing functional groups were involved in the binding of gold. 47 The structure of the COP adsorbent was further investigated by XRD, as shown in Fig. 8b, and the diffraction peaks at 38.3, 44.7, 64.9, and 77.8 can be observed, corresponding to gold (111), (200), (220), and (311) of the lattice plane. 48 It shows that N-TPCOP can reduce Au 3+ to gold monocrystals. ...
With the widespread use of gold as a precious metal, the recovery of gold has become an urgent problem to be solved. Therefore, the design and preparation of a sorbent with better adsorbability and higher selectivity for Au(iii) is of great significance for recovering gold resources and protecting the environment. In order to obtain an efficient and stable gold ion sorbent, N1,N1′-(1,4-phenylene)bis(N1-(4-aminophenyl)benzene-1,4-diamine) and 2,4,6-tricarboxylisophene were cross-linked by a solvent thermal reaction to synthesize a double-functional covalent organic polymer (N-TPCOP). The N-TPCOP has a very high gold uptake capacity of 3400.38 mg g⁻¹, because it reduces Au(iii) to elemental gold by sequestration and redox reactions between functional atoms (N and O) and Au(iii). In summary, we have verified the adsorption potential of a novel covalent organic polymer for Au(iii), which provides a strong reference for the recycling of precious metal gold in secondary resources and the protection of environmental resources.
... Gold, a rare and precious metal, has been extensively used for various applications such as an anti-aging agent in cosmetics [1], a highly efficient catalyst in organometallic chemistry [2][3][4][5], a highly electrical conductor in the electronic industry [6], a nanoparticle substrate [7][8][9], and a bioactive ingredient in pharmaceuticals [10,11]. Recently, gold ions were used as a therapeutic agent that shows excellent biocompatibility in medication for treatment in a wide variety of diseases including rheumatic arthritis, asthma, cancer, AIDS, bronchial asthma, malaria and brain lesions [12][13][14][15][16][17]. ...
Novel dihydroquinoline derivatives (DHP and DHP-OH) were synthesized in one pot via a tandem trimerization-cyclization of methylpropiolate. DHP and DHP-OH possess strong blue fluorescence with high quantum efficiencies over 0.70 in aqueous media. DHP-OH displays a remarkable fluorescence quenching selectively to the presence of Au3+ through the oxidation of dihydropyridine to pyridinium ion as confirmed by NMR and HRMS. DHP-OH was used to demonstrate the quantitative analysis of Au3+ in water samples with the limit of detection of 33 ppb and excellent recovery (>95%). This fluorescent probe was also applied for the determination of Au3+ residue in the gold nanoparticle solution and a paper-based sensing strip for the on-site detection of Au3+.
... Therefore, an economical, efficient and environment-friendly method for the selective dissolution of copper is a key technology for precious metal recovery. The existing separation techniques are mainly based on the optimization of the selective leaching process and the separation of precious metals in the leachate, such as multi-step leaching with H 2 SO 4 /H 2 O 2 -thiourea/triferric ion (Birloaga and Vegliò, 2016), solvent extraction by diisoamyl sulfide (Zhang and Zhang, 2014), adsorption with polyethylenimine (PEI) modified Lagerstroemia speciosa leaves powder (Choudhary et al., 2018), separation of metals and nonmetals with slurry electrolysis (Yang et al., 2018), and the like. Due to the heterogeneity and complexity of the components, PCB recycling is still subject to many restrictions. ...
The present study reports a sequential, non-acid process for effective recovery of copper and precious metals from mobile phone printed circuit boards. In this process, gold and silver were first enriched during the synthesis process of cuprous chloride and then leached by thiosulfate method. Results indicated that the distribution of gold and silver in the liquid and solid phases during the synthesis of cuprous chloride process was affected by the [Cu]/[Cu²⁺] ratio. Enrichment of gold and silver in the residue after the cuprous chloride synthesis could be achieved by the adjusting the [Cu]/[Cu²⁺] ratio. The silver and gold leaching rates of the residue after cuprous chloride synthesis (93.8 % silver and 99 % gold) were much higher than those of the raw PCB sample (27.0 % silver and 14.2 % gold) under the same conditions. This process has the advantages of high leaching efficiency, high leaching rate and avoiding the use of HNO3 or aqua regia commonly used for copper, gold and silver recovery. Thus, this study offers a promising and environmentally friendly method for recovering valuable metals from e-waste.
... A study using raw biomass as biosorbent demonstrated very high Au recovery. The refining of Au in a local gold processing factory in India was also used to obtain sludge and jewelry polishing wastewater [341]. AuNPs are produced in many academic and industrial laboratories using chemical techniques, which allow them to be produced with various morphologies and sizes. ...
Agriculture and industrial wastes (AIWs) have attracted much attention because of their huge environmental, economic, and social impacts. AIWs have been considered a crucial link of a closed-loop for the fabrication of nanomaterials and composites wherein they replace traditional resources with sustainable waste in waste management. In this context, the proper disposal of AIWs is required. This review aims to investigate the technical feasibility of using innovative AIW resources and various strategies for the fabrication of nanomaterials for improving energy applications. First, the utilization of AIWs is classified comprehensively. Second, key technologies to produce nanomaterials are summarized. In addition, this review discusses the potential applications of the fabricated nanomaterials in energy storage and energy conversion.
In consideration of the increasing demand for gold and the scarcity of mineral resources, this approach represents a promising avenue for the recovery of gold from secondary resources. In this...
Recycling gold from electronic waste offers significant benefits for both environmental protection and resource sustainability. However, this process presents considerable challenges due to high costs, prolonged processing times, and interference from coexisting metals. In this study, we synthesized a hybrid mesoporous nanocomposite comprising platelets-like CoNi2S4 incorporated with g-C3N4 nanosheets (CoNi2S4@g-C3N4) for the selective recovery of gold (Au(iii)) ions from spent computer motherboards. Comprehensive characterization of the CoNi2S4@g-C3N4 nanocomposite was conducted, including its physicochemical properties, textural and structural characteristics, morphology, and elemental composition. The CoNi2S4@g-C3N4 extractor demonstrated an exceptional adsorption capacity of 200.6 mg g⁻¹, with high selectivity at pH 2, rapid equilibrium time of 60 minutes, and satisfactory reusability for over ten cycles. Adsorption isotherm and kinetic studies revealed that the CoNi2S4@g-C3N4 nanocomposite adheres to the Langmuir adsorption model and the pseudo-second-order kinetic model for Au(iii) ion adsorption. Overall, this study introduces a viable adsorbent that shows considerable promise for industrial-scale Au(iii) extraction from e-waste.
The fouling phenomenon of membranes has hindered the rapid development of separation technology in wastewater treatment. The integration of materials into membranes with both excellent separation performance and self‐cleaning properties still pose challenges. Here, a self‐assembled composite membrane with solar‐driven self‐cleaning performance is reported for the treatment of complex oil‐water emulsions. The mechanical robustness of the composite membrane is enhanced by the electrostatic attraction between chitosan and metal–organic frameworks (MOF) CuCo‐HHTP as well as the crosslinking effect of glutaraldehyde. Molecular dynamics (MD) simulations also revealed the hydrogen bonding interaction between chitosan and CuCo‐HHTP. The composite membrane of CuCo‐HHTP‐5@CS/MPVDF exhibits a high flux ranging from 700.6 to 2350.6 L∙m⁻²∙h⁻¹∙bar⁻¹ and excellent separation efficiency (>99.0%) for various oil–water emulsions, including crude oil, kerosene, and other light oils. The addition of CuCo‐HHTP shows remarkable photothermal effects, thus demonstrating excellent solar‐driven self‐cleaning capability and antibacterial performance (with an efficiency of ≈100%). Furthermore, CuCo‐HHTP‐5@CS/MPVDF can activate peroxomonosulfate (PMS) under sunlight, quickly removing oil‐fouling and dyes. Density functional theory (DFT) calculations indicate that the bimetallic sites of Cu and Co in CuCo‐HHTP effectively promoted the activation of PMS. This study provides distinctive insights into the multifaceted applications of MOFs‐derived photothermal anti‐fouling composite membranes.
This study investigates the development of carbon-silica composite (CSC) adsorbents with tuneable surface properties for gold adsorption from silica and molasses. Nitrogen modification of the CSC adsorbents was achieved Gold
through a facile urea impregnation onto the CSC, followed by pyrolysis at 400 °C (400C-5A). Exceptional Au(III) D Molasses
adsorption was demonstrated from acidic solutions, with a maximum adsorption capacity of 416.9 mg g−1. While Carbon
Urea
CSC with no nitrogen modification (400C) only exhibits an adsorption capacity of 337.9 mg g−1. Langmuir Chelation
isotherm model and pseudo-second order kinetic model were found to best describe the adsorption behaviour for E
Au(III) sorption on both nitrogen-modified and non-modified CSC. Urea modification led to nitrogen containing graphitic, pyridinic and pyrrolic functionalities, of which pyridinic groups were active sites for metal coordina- tion, leading to enhanced adsorption and high selectivity towards Au and Pd. Au adsorptions of greater than T
99.8% were revealed using both modified and unmodified CSC, even at low concentrations of gold (5 or 10 ppm). X-ray Photoelectron spectroscopy (XPS) analysis of 400C-5A following adsorption indicated the pres- ence of both Au(0) and Au(III), demonstrating that adsorption took place through both chelation and an adsorp- tion-reduction mechanism. These effective adsorbents derived from abundantly available, low cost, bio-based C
chemicals or low value by-products could create new opportunities for Au and/or Pd adsorption from acidic solution.
To achieve the mutual separation of yttrium(Y(III)) and strontium(Sr(II)) from acidic solution, a diglycolamic acid-grafted adsorbent (DGAA−Si adsorbent) was successfully developed via a facile amidation reaction between diglycolic anhydride and a 3-aminopropyl-functionalized silica-gel. The adsorption performances of DGAA−Si adsorbent toward Y(III) and Sr(II) were systematically investigated in terms of the effect of the acid concentration etc. The particle-induced X-ray emission analysis method was used to study the adsorption behavior in the solid-state and elucidated the distribution conditions of the adsorbed Y(III) and Sr(II). Moreover, the mutual separation of Y(III) and Sr(II) was successfully achieved using acid in different concentration as an effluent solution.
The design and synthesis of efficient adsorbents for the recovery of precious metals from secondary resources are of great environmental and economic significance. Herein, a magnetic sulfur‐doped composite CoFe 2 O 4 @S–CoWO 4 (CF@S–CoWO 4 ) is developed through a hydrothermal synthesis method, which is used to selectively recover gold in aqueous media. Significantly, CF@S–CoWO 4 exhibits the best overall performance with gold ions adsorption capacity ( Q max ) and distribution coefficient ( K d ) are 1049 mg g ⁻¹ and 4.4 × 10 ⁶ mL g ⁻¹ , respectively, which are much higher than those of other gold adsorption materials. The selectivity coefficients ( K ) toward other metal ions (Pd ²⁺ , Ca ²⁺ , Mg ²⁺ , Cd ²⁺ , Al ³⁺ , Li ⁺ , Ni ⁺ ) are also higher, which suggests that CF@S–CoWO 4 had a preferential selectivity for Au ³⁺ in coexisting ion solutions. Moreover, the antianion interference of the composite follows the order: SO 4 ²⁻ > PO 4 ³⁻ > NO 3 ⁻ > CO 3 ²⁻ , and it also shows very good reusability with adsorption efficiency at 81.78% after four repeated cycles. Based on characterizations and calculation, it is found that Au(III) mainly undergoes chelation and reduction reactions in the S sites in CF@S–CoWO 4 , which indicates the important role of S sites. Hence the CF@S–CoWO 4 composite demonstrates a promising application for the recycling of gold ions from electronic wastewater.
To face the current critical challenges of gold recovery and beneficial utilization of solid waste, this study synthesized diatom biochar from the anoxic pyrolysis of diatoms and proved the superiority of the diatom biochar as a novel adsorbent for Au(III) in both synthetic and real electroplating wastewaters. The diatom biochar was found to have a high adsorption capacity of 443.0 mg/g and a superior recovery efficiency of up to 92.1%. The Au(III) adsorption kinetics followed the pseudo-second-order and intraparticle diffusion models. Electrostatic attraction and reduction were detected as the major adsorption mechanisms. An exceptional selectivity was also observed for the diatom biochar toward Au(III) with other coexisting heavy metals. Even in the presence of CN⁻ in the solution, the diatom biochar still exhibited superiority in Au(III) adsorption. Owing to its high affinity to Au(III), the diatom biochar was successfully applied in real electroplating wastewater containing trace Au(III), with an adsorption efficiency as high as 96.7%. These findings sufficiently demonstrate the excellent performance and economic feasibility of diatoms for Au(III) recovery from electroplating wastewater, which also promoted solid waste minimization of diatom biorefineries.
The aim of this study was to develop cellulose-based, fibrous adsorbents for the selective recovery of gold (Au) and to reveal the adsorption–reduction–attachment–aggregation mechanism. Polyethylenimine (PEI)-functionalized cellulose fibers (PCFs) were fabricated by extruding a mixture of PEI and cellulose into a sulfuric acid solution. To maximize the performance of the PCFs, the amounts of PEI and ethylene glycol diglycidyl ether, a crosslinking agent, were optimized. The maximum uptake of Au(III) by PCFs was 1108.2 ± 58.8 mg/g obtained based on adsorption isotherm experiments. PCFs characterization and mechanistic investigations were carried out using FT-IR, XPS, XRD, FE-SEM, EDX, and HR-TEM. After 0.5 h of Au(III) adsorption on the PCFs, Au(III) was reduced to Au(I) owing to electron transfer when –NH3⁺/−NH2⁺‒, functional groups of PCFs, were oxidized to = NH⁺‒ and = N‒. After 12 h, –NH3⁺/−NH2⁺‒ were oxidized to = N‒, and C–N was oxidized to C[dbnd]O; therefore, Au(I) present on the fibers was reduced to Au(0) owing to the oxidation–reduction reaction. The released nitrogen was detected as NO2⁻ and NO3⁻ in the solution. Subsequently, the Au particles detached from the PCFs, and the aggregated Au particles on the vessel wall were recovered. In addition, the prepared PCFs showed outstanding selectivity for Au(III) in a solution containing the main metals found in electronic waste. PCFs maintain the Au(III) adsorption performance even in the 10 times adsorption-desorption cycles. These results indicated the application potential of PCFs as efficient adsorbents for Au recovery.
A non-solvent-induced phase separation method was used to synthesize easily separable membrane materials from polyether sulfone and polym-phenylenediamine to achieve selective recovery of Au from e-waste solutions. The optimum conditions, adsorption capacity, and selectivity of the polyether sulfone/polym-phenylenediamine membrane were investigated by adsorption experiments. The maximum adsorption capacity of the PES/PmPD membrane to Au(III) within 4 h at 30 oC with optimal pH of 1 was 582.75 mg/g. The adsorption process follows the quasi-second-order adsorption isotherm. The adsorption agent was characterized by XPS and XRD to understand the recovery mechanism of Au(III) by PES/PmPD membrane. In addition, PES/PmPD membranes were single-selective for Au(III) in a variety of natural water bodies and highly acidic conditions. Therefore, the thin membrane material has great potential for recycling Au(III) from waste e-waste.
To develop a PENG with both good comfort and high performance, we designed a wearable Ag/PEI/Cotton fabric electrode. Herein, PEI was used as a bridge to connect the Ag nanoparticles with cotton fabric by the LbL self-assembly method. The sheet resistance of the Ag/PEI/Cotton fabric electrode reached 1.6 × 10⁻⁴ Ω·cm. We found that the Ag/PEI/Cotton fabric electrode was more flexible and had better mechanical properties than the Cu metal electrode. The Ag/PEI/Cotton fabric electrode also showed good antibacterial activity, suggesting that it could be safely used as a fabric in contact with human skin. Since the Ag/PEI/Cotton fabric electrode had a low sheet resistance, it could be used as a replacement for the metal electrode traditionally used in composite PENGs. The output voltage and output current of the BT/PVDF-Ag/PEI/Cotton composite PENG were 1.8 V and 0.37 μA, respectively, and the output voltage was stable after 1500 cycles. The composite PENG prepared with the Ag/PEI/Cotton fabric electrode could sense various types of human motion. Herein, we provide a new method to fabricate a wearable fabric-based electrode, that can replace the conventional metal electrode to prepare composite PENGs. The BT/PVDF-Ag/PEI/Cotton composite PENG has extensive application prospects in motion monitoring and wearable devices.
An adsorbent (PEI‐GA) is prepared by crosslinking polyethyleneimine with glutaraldehyde. PEI‐GA shows outstanding adsorption performance towards Au(III) and Pd(II). PEI‐GA presents large adsorption capacity towards Au(III) in a wide application pH range from 1 to 9. The adsorption capacities of PEI‐GA for Au(III) and Pd(II) at 25°C reach 2575 and 497 mg/g, respectively. Au(III) and Pd(II) can be adsorbed completely within 10 min for 8.3 mg/L Au(III) and 20 min for 9.7 mg/L Pd(II). The adsorption equilibrium time required for 523.9 mg/L Au(III) and for 565.6 mg/L Pd(II) is 2 and 9 h, respectively. The Sips model is the most suitable to describe the adsorption isotherms which leads to more realistic adsorption capacities for both metals. PEI‐GA also exhibits high selectivity and repeatability towards Au(III) and Pd(II). The adsorption mechanism involves redox, chelation coordination, and electrostatic interactions for Au(III), and coordination and electrostatic interactions for Pd(II).
Recovering precious gold Au(III) ions from aqueous solution not only has a large economic incentive but also bears a significant environmental impact. One longstanding challenge is to obtain fast, effective and selective Au(III) adsorption without performance degradation. In this paper, a series of novel water-insoluble triazine-crosslinked polyethyleneimines (referred as TCPEIs, s stands for the molar ratio of amino to chlorine and s = 2, 4, 6, 8, 10) are designed and synthesized as adsorbents for Au(III) recovering from waste solutions. Excitingly, TCPEIs, TCPEI6 in particular, not only have high adsorption capacity, but also exhibit an unprecedentedly high adsorption rate. Langmuir monolayer adsorption capacities of TCPEI6 were calculated as 5462 mg/g. The adsorption efficiency of 95.6 % within 10 s with a capacity of 1073.0 mg/g and the recovering rate constant is more than 10 times greater than the best Au(III) adsorbents reported so far. Such excellent adsorption performance is mainly attributed to electrostatic interaction, complexation and the mechanical stability of TCPEIs. Furthermore, TCPEIs was regenerated within one minute to completely release the adsorbed Au(III) ions and the regenerated TCPEIs was used again for adsorb Au(III) ions, showing no apparent performance degradation, demonstrating the very attractive prospect for TCPEI6 in precious metal ion recovery.
Enrichment of gold (Au) from wastewater is an efficient use of non-renewable resources and can reduce environmental pollution. Here, A new adsorbent (UiO-66-ES) is created that efficiently captures Au(III) in simulated wastewater by altering UiO-66-NH2 with poly(ethylene sulfide). The adsorbent was successfully prepared as confirmed by FT-IR, SEM, EDS, BET, XRD and XPS. At 318 K and a pH of 4.0, the highest removal ability of UiO-66-ES for gold ions is 723.005 mg/g. Kinetic studies revealed that Au(III) chemisorption on UiO-66-ES was the main driving force in the process. The recovery of Au(III) by UiO-66-ES happened as a monolayer adsorption over a uniform surface, according to the isotherm investigation. Meanwhile, thermodynamic analyses revealed that the adsorption is a heat-absorbing and natural phenomenon. Moreover, after four adsorption–desorption cycles, UiO-66-ES still achieved 89.83% adsorption and 86.43% desorption. In simulated wastewater comprising seven metallic ions, the adsorbent is extremely specific for Au(III). The adsorption mechanism of Au(III) includes electrostatic attraction, chelation, and reduction, according to zeta and XPS data. Since its high adsorption capacity, great selectivity, and good repeatability, UiO-66-ES is projected to be used in the practice of gold (Au) recovery from wastewater.
Novel dihydroquinoline derivatives (DHP and DHP-OH) were synthesized in one pot via a tandem trimerization-cyclization of methylpropiolate. DHP and DHP-OH possess strong blue fluorescence with high quantum efficiencies over 0.70 in aqueous media. DHP-OH displays a remarkable fluorescence quenching selectively to the presence of Au3+ through the oxidation of dihydropyridine to pyridinium ion as confirmed by NMR and HRMS. DHP-OH was used to demonstrate the quantitative analysis of Au3+ in water samples with limit of detection of 32.8 ppb and excellent recovery (>95%). This fluorescent probe was also applied for determination of Au3+ residue in the gold nanoparticle solution and paper-based sensing strip for on-site detection of Au3+.
This study aimed to apply an adsorption-based technique to directly suppress harmful algal blooms (HABs) in freshwater without causing secondary pollution. Considering the negative surface charge of the representative harmful cyanobacteria Microcystis aeruginosa of HABs in the aqueous phase, a stable and aminated sorbent polyethylenimine–polyvinyl chloride composite fiber (PEI–PVC) was applied to remove M. aeruginosa cells from the aqueous solution. The PEI–PVC fiber could directly and efficiently remove approximately 90 % of harmful cyanobacterial cells in artificial media and approximately 80 % of HABs in real environmental water without any cell lysis or destruction. During the HAB treatment process using PEI–PVC, the amount of microcystins (MCs) in the test sample was continuously decreased by simultaneous adsorption on the PEI–PVC. The PEI–PVC fiber used in this study was regenerable through desorption using an alkaline solution, and the regenerated adsorbent showed a similar cell removal efficiency to that of the original adsorbent. In addition, under light exposure, the PEI–PVC fiber did not elute any toxic chlorine into the solution, whereas pristine PVC fiber increased the chlorine concentration in the aqueous solution through photodegradation. Consequently, the adsorption-based method using PEI–PVC fiber could be a feasible and stable method for counteracting HAB contamination of water resources.
A thiourea-modified weak base anion exchange resin, ZGA451 ([email protected]), was prepared. [email protected] exhibited excellent potential for Au(III) adsorption. The maximum adsorption capacity of Au(III) by [email protected] was 995.6 mg/g at 298 K. The adsorption process followed the Freundlich and pseudo-second-order models, which are monolayer and chemisorption adsorption, respectively. The adsorption mechanism of Au(III) on [email protected] involves electrostatic attraction, chelation, and redox. Thermodynamic experiments showed that the reaction exhibited spontaneous endothermic behavior. Thus, [email protected] possesses outstanding Au(III) adsorption properties.
It is a clear and present problem to separate precious metals from metallurgical wastewater selectively. In this study, an adsorbent is prepared via polyethyleneimine crosslinked by trimesoyl chloride ([email protected]), and then used to adsorb Au(III) and Pd(II). [email protected] has excellent and stable adsorption properties for Au(III) at pH = 1–9. [email protected] exhibits faster adsorption rate for Pd(II) than Au(III). Adsorption equilibrium time of Au(III) and Pd(II) at 10 mg/L are 20 min and 15 min, respectively. The maximum adsorption capacity of [email protected] for Au(III) and Pd(II) are 953.98 mg/g and 369.05 mg/g, respectively. In addition, [email protected] shows outstanding ions selectivity and reusability for Au(III) and Pd(II) adsorption. The adsorption of Au(III) by [email protected] is an endothermic process, while the adsorption of Pd(II) is an exothermic process. Adsorption kinetics of Au(III) and Pd(II) by [email protected] is suitable for pseudo second-order kinetic model. There exist electrostatic adsorption, redox reaction and chelation during adsorption of Au(III) by [email protected] Adsorption of Pd(II) by [email protected] is accompanied by chelation.
Thiourea-modified Cu2O (Cu2O-TU) was prepared by a facile route and used for the selective recovery of gold in acidic solution. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis elucidated that Au (III) ions were adsorbed onto the surface of Cu2O-TU via the electrostatic attraction of surface protonated amines groups (-NH3⁺) with AuCl4⁻ and the chelating interaction of pyrrole-type nitrogen as well as CS groups in the pH range of 1.0 – 5.0. Subsequently, partial adsorption of Au (III) was reduced to Au (I) and Au (0), while pyridine-type nitrogen was oxidized to -NO, which accelerated the adsorption rate of Au (III). The adsorption equilibrium time was about 2 min and the adsorption capacity was 79.7 mg·g⁻¹ at a pH value of 2.0 in 40 mg·L⁻¹ Au (III) solution. The fitted result of gold adsorption by the Langmuir model was 1529.4 mg·g⁻¹ at 318 K. The experimental data conformed to the pseudo-second-order model, indicating that the adsorption process was chemisorption. After 5 cycles, the capability of adsorption only decreased by 7.43%, which provided a great possibility for its application in solutions. Besides, Cu2O-TU showed specific and selective adsorption ability for Au (III) in the outdoor environment.
Agriculture and industrial wastes (AIWs) have attracted much attention because of their huge environmental, economic, and social impacts. AIWs have been considered a crucial link of a closed-loop for the fabrication of nanomaterials and composites wherein they replace traditional resources with sustainable waste in waste management. In this context, the proper disposal of AIWs is required. This review aims to investigate the technical feasibility of using innovative AIW resources and various strategies for the fabrication of nanomaterials for improving energy applications. First, the utilization of AIWs is classified comprehensively. Second, key technologies to produce nanomaterials are summarized. In addition, this review discusses the potential applications of the fabricated nanomaterials in energy storage and energy conversion.
A novel sulfydryl-modified MOF (UiO-66-MSA) was prepared by externally optimizing UiO-66-NH2 with mercaptomalic acid (MSA) and its capacity in selective recovering of Au(III) from solution was examined. Tests indicated that external modification of UiO-66-NH2 by MSA increased its theoretical maximal adsorption capacity at pH 5 by 24.57% from 578.0 to 720.0 mg/g. Simulation of the kinetics data revealed that Au(III) binding on both UiO-66-MSA and UiO-66-NH2 followed the pseudo-second-order model, with the former material having significantly higher kinetics. In the existence of competing ions, Au(III) recovery by sulfydryl-modified UiO-66-NH2 (UiO-66-MSA) was enhanced by 26.53% from 72.06% to 98.59% at an initial Au(III) concentration of 56.9 mg/L. This material also had a fairly good reusability. At 5 times of regeneration, it was still able to capture 99.42% Au(III) from solution. Analysis of the changes in XPS patterns and the electrokinetic properties of UiO-66-MSA suggested that Au(III) binding on this MSA-modified MOF was complex. Electrostatic interaction, reduction and chelation may have all actively participated in the adsorption process. DFT calculation revealed that Au(III) binding was attributed to the -SH, -NH and C=O functional groups residing on the repeating unit of UiO-66-MSA, with its sulfhydryl functional group being the strongest binding site.
In this paper, PEI-Alginate fibers were prepared using a more environmentally friendly method for the recovery of gold (Au (III)) from acidic wastewater. Adsorption results show that PEI plays a major role in the recovery of Au (III), and the maximum adsorption capacity of Au (III) was 644.92 ± 43.06 mg/g calculated by Langmuir model at pH 1, 25 °C. In addition, the constants k1 and k2 was 0.7044 ± 0.1038 L/min and 0.0025 ± 0.0002 g/mg min were calculated by pseudo-first-order and pseudo-second-order, which was outstanding compared to the most of the adsorbents reported in the literature. The mechanism of adsorbent preparation, characterization of adsorbents and adsorption-reduction mechanism of Au (III) were analyzed by Field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The results showed that Au (III) was adsorbed by electrostatic attraction between protonated nitrogen-containing functional groups (=NH+-, and –NH2+-/-NH3+) and AuCl 4−. Furthermore, Au (III) was reduced to Au(I) and Au (0) during the adsorption process, and -NH-/-NH2, –NH2+-/-NH3+, and C-O provided electrons for Au (III) reduction and then they were oxidized to =N-, =NH+-, and C=O, respectively.
Naturally available biomass can be explored as a potential sorbent for recovery of precious metals. This work evaluates the sorption potential of a biosorbent developed by host soluble tannins cross-linked Lagerstroemia speciosa leaves powder (TLS) for Pd recovery from secondary waste. Batch experiments suggest 95% Pd(II) sorption by TLS is achieved over a pH range of 1-6 with a maximum of 99% at pH 2. The experimental data for Pd(II) sorption onto TLS is well explained by pseudo-second-order kinetics and Langmuir isotherm model with a monolayer sorption capacity of 46.3 mg/g. Thermodynamic variables indicate that Pd(II) sorption onto TLS is spontaneous, endothermic, and physical in nature. TLS biosorbent was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy (XPS). XPS results reveal the presence of zero-valent Pd and mono or divalent Pd species on the TLS surface, which conclude that Pd(II) removal is governed by a sorption-reduction mechanism. The TLS is effective in Pd(II) recovery from the acid-leached solution of monolithic ceramic capacitors (A-MLCC) and simulated spent automobile catalyst (A-SSAC), which suggest that this biosorbent can be used as a promising material in biotechnological processes for recovery of precious metals from secondary waste.
We report a rapid method of green chemistry approach for synthesis of gold nanoparticles (AuNPs) using Lagerstroemia speciosa leaf extract (LSE). L. speciosa plant extract is known for its effective treatment of diabetes and kidney related problems. The green synthesis of AuNPs was complete within 30 min at 25°C. The same could also be achieved within 2 min at a higher reaction temperature (80°C). Both UV–visible spectroscopy and transmission electron microscopy results suggest that the morphology and size distribution of AuNPs are dependent on the pH of gold solution, gold concentration, volume of LSE, and reaction time and temperature. Comparison between Fourier transform infrared spectroscopy (FT-IR) spectra of LSE and the synthesized AuNPs indicate an active role of polyphenolic functional groups (from gallotannins, lagerstroemin, and corosolic acid) in the green synthesis and capping of AuNPs. The green route synthesized AuNPs show strong photocatalytic activity in the reduction of dyes viz., methylene blue, methyl orange, bromophenol blue and bromocresol green, and 4-nitrophenol under visible light in the presence of NaBH4. The non-toxic and cost effective LSE mediated AuNPs synthesis proposed in this study is extremely rapid compared to the other reported methods that require hours to days for complete synthesis of AuNPs using various plant extracts. Strong and stable photocatalytic behavior makes AuNPs attractive in environmental applications, particularly in the reduction of organic pollutants in wastewater.
There is widespread consensus that landfill of waste electronic and electric equipment is not an acceptable end-of-use management
option. Diversion from landfill, either through voluntary or mandatory take-back and collection programs, overwhelmingly leads
to the recycling of e-waste, which typically consists of the recovery of a limited number of metals. Cell phones are currently
one of the few electronic products, if not the only one, that also have a thriving reuse market. In fact, more handsets are
reused than recycled. Cell phones therefore offer the rare opportunity to compare closed-loop supply chains for e-waste reuse
and recycling. In this paper, we examine the economics of cell phone reuse and recycling based on detailed primary data collected
from reverse logistics, reuse and recycling operations in 2003 in the UK and in 2006 in the US. We show that while cell phone
reuse has a healthy profit margin, handset recycling is currently a by-product of reuse.
KeywordsWEEE-Cell phones-Reuse-Recycling-Production economics-Closed-loop supply chains
Gold (Au) is one of the precious metals whose availability, use and recovery represent important problems from the economic and environmental point of view. The synthesis of the novel acrylic copolymer bearing dimethylaminobenzaldehyde functional groups (AS–5BA) was carried out in three stages. The structure of the synthesized material was evidenced by infrared spectroscopy (IR) and its morphology by scanning electron microscopy (SEM), while the elemental composition was determined through X-ray photoelectron spectroscopy (XPS). The AS–5BA functionalized copolymer was used for gold sorption from chloride solution by the batch method. The effects of HCl medium acidity, initial Au(III) concentration, and contact time on the Au(III) retention were studied. The maximum Au(III) sorption capacity was evaluated as 87.75 mg/g. The copolymer under study exhibited strong selectivity for the gold in the binary Au(III)-Co(II), Au(III)-Mn(II) and Au(III)-Cd(II) solutions. Gold could be quantitatively desorbed from the loaded sorbent with acidic solution of thiourea at ambient temperature. The developed AS–5BA copolymer was successfully applied to recover gold from a wastewater collected from a gold jewelry manufacturing plant. The AS–5BA functionalized acrylic copolymer with N as donor atoms has good durability as well as good efficiency for its repeated use for gold removal from aqueous solutions.
In this study, Poly(glycidyl methacrylate) (PGMA) was grafted onto the surface of the weak basic D301 resin. Subsequently, two new adsorbents, D301-g-EDAPGMA and D301-g-THIOPGMA, were obtained successfully through ringopening reactions between the epoxide rings of PGMA and the amine of ethylenediamine and thiourea. The adsorption and recognition properties of these two adsorbents for AuCl4⁻ were studied through batch method. The experimental results showed that D301-g-EDAPGMA and D301-g-THIOPGMA possess strong adsorption ability and excellent recognition selectivity for AuCl4⁻, and pH has a great influence on the adsorption capacity in the studied pH range. The adsorption of D301-g-EDAPGMA and D301-g-THIOPGMA towards AuCl4⁻ is a typical monomolecular layer adsorption. The adsorption capacity of D301-g-EDAPGMA and D301-g-THIOPGMA for AuCl4⁻ reaches 274.7 and 300.4 mg·g⁻¹ at 298 K and pH of 2, respectively. D301-g-EDAPGMA and D301-g-THIOPGMA can be used to adsorb AuCl4⁻ electively from gold-bearing chloride solution. In addition, the desorption of AuCl4⁻ from adsorbent is effective using mixture of acetone and 1 mol·L⁻¹ of hydrochloric acid as eluent. Consecutive adsorption-desorption experiments showed that D301-g-EDAPGMA and D301-g-THIOPGMA could be reused with 1.9% of adsorption capacity loss.
In this study, the polyethyleneimine modified activated carbon/Fe (PAF) was prepared and used as an effective magnetic adsorbent to remove uranium (U(VI)) ions from aqueous solution as a function of batch adsorption parameters. The developed magnetic adsorbent was investigated by FT-IR, SEM, EDX, TG/DSC and BET techniques. The effects of the adsorption parameters on the sorption amount were investigated by using factorial design. In order to study the sorption behavior for U(VI) ions, the Langmuir, and Freundlich isotherm models were applied to fit the equilibrium data. The monolayer adsorption capacity of the magnetic sorbent for U(VI) was determined to be 115.31 mg g⁻¹ at pH 5, 20 °C and 60 min. The kinetic results indicated that the pseudo-second-order kinetic modeling fits the equilibrium data well under employed temperature conditions. The thermodynamic examinations showed exothermic and spontaneous adsorption process. The reusability-cycling test indicated that the magnetic sorbent has good desorption performance. It was also concluded that the PAF magnetic material can be used as an effective adsorbent for the removal of U(VI) ions from wastewaters by taking into account its advantages such as being of cost effective, easy prepare and environmental friendly.
In order to develop an industrially applicable method for the use of phosphine oxide-based powder material for the capture and concentration of platinum group metals (PGM) from acidic effluents, a two stage process is proposed in this work. The process steps involve coupling the metal sorption on the powder in a continuous stirred tank reactor (CSTR) with a microfiltration PTFE membrane enabling a subsequent stripping of the metals concentrated on the powder material using an acidified solution of thiourea. Using a model solution with 0.6 mM Pd(II) in HCl and common metals as impurities (0.6mM of Ni(II) and Cu(II) each), the process was conducted for several cycles leading to the final solution containing up to 9.8 mM of Pd(II) with a purity of around 90%. In addition, this process was successfully applied to a leachate of a car catalyst converter, that contained not only palladium, but also platinum, rhodium, as well as large excess of aluminum, cerium and iron. We have thus arrived at a robust process for concentrating effluents containing precious metals, achieving high concentration factors and purities of the final stream, while having low material loss and/or fouling of equipment.
In the current work, a graphene oxide coated water hyacinth biochar composite (WHB-GO) was synthesized to remove Cr(VI) from aqueous solution. The biomass feedstock was firstly treated with graphene oxide and then annealed at 300 degrees C in a quartz tube furnace under N-2 atmosphere. After synthesis, full characterization with various techniques (SEM, FT-IR, XPS and BET) were used to analyze the properties of the adsorbent and the sorption mechanisms of Cr(VI). The effects of pH, ionic strength, sorption kinetics, isotherms and thermodynamics, as well as comparison and regeneration experiments were also investigated. The results indicated that the adsorption capacity was significantly influenced by pH and ionic strength. The maximum adsorption capacity (150.02 mg g(-1)) of the WHB-GO was obtained at pH 2.0 and 50 degrees C. Besides, the sorption data could be fitted well by pseudo-second-order and Freundlich models. The thermodynamic studies indicated that the adsorption reaction was a spontaneous and endothermic process. The enhanced adsorption of Cr(VI) on the WHB-GO was mainly controlled by electrostatic attraction and reduction of Cr(VI) coupled with Cr(III) complexation. The regeneration study revealed that WHB-GO could be reused almost six times without loss of activity in adsorption tests. Overall, WHB-GO can be used as a novel, facile, and low-cost sorbent for the removal of Cr(VI) from aqueous solution.
This study presents the applicability and reusability of polyethylenimine (PEI)-coated polysulfone/Escherichia coli biomass composite fiber (PEI-PSBF) as a biosorbent for recovery of Pd(II) from acidic solutions. To enhance accessible surface area for Pd(II), PEI-PSBF was fabricated by first extruding polysulfone/biomass blend into water, next coating with PEI onto the surface of the polysuflone/biomass composite fiber (PSBF), and finally cross-linking with glutaraldehyde. In batch sorption experiments, adsorption capacity of the PEI-PSBF for Pd(II) was compared with that of PSBF to investigate the enhancement by PEI coating on adsorption. In result, the sorption kinetics and isotherms showed that the sorption kinetics of Pd(II) was fast, and the maximum sorption capacity of PEI-PSBF was 7.0 times higher than that of PSBF. Additionally, it was observed that the sorption capacity of PEI-PSBF was significantly depended on the HCl concentration and the optimal range of HCl concentration to achieve high sorption capacity was found to be 0.1-1 M. After adsorption, Pd(II) loaded on the PEI-PSBF could be recovered using a mixture of 0.1 M HCl and 0.01 M thiourea solution. The desorption efficiency of the mixture was approximately 97.4%. Finally, in regeneration test of the biosorbent, it was confirmed that the PEI-PSBF can be regenerated at least five times.
In this study, a method inspired by polyphenol chemistry is developed for the facile preparation of microcapsules under mild conditions. Specifically, the preparation process includes four steps: formation of the sacrificial template, generation of the polyphenol coating on the template surface, crosslinking of the polyphenol coating by cationic polymers, and removal of the template. Tannic acid (TA) is chosen as a representative polyphenol coating precursor for the preparation of microcapsules. The strong interfacial affinity of TA contributes to the formation of polyphenol coating through oxidative oligomerization, while the high reactivity of TA is in charge of reacting/crosslinking with cationic polymer polyethyleneimine (PEI) through Schiff base/Michael addition reaction. The chemical/topological structures of the resultant microcapsules are simultaneously characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), Fourier Transform infrared spectroscope (FTIR), X-ray photoelectron spectroscopy (XPS), etc. Wall thickness of the microcapsules could be tailored from 257±20 nm to 486±46 nm through changing the TA concentration. The microcapsules are then utilized for encapsulating glucose oxidase (GOD), and the immobilized enzyme exhibits desired catalytic activity and enhanced pH and thermal stabilities. Owing to the structural diversity and functional versatility of polyphenols, this study may offer a facile and generic method to prepare microcapsules and other kinds of functional porous materials.
This study investigates the potential application of the polyethyleneimine- (PEI) and amidoxime-modified Spirulina (Arthrospira) platensis biomasses for the removal of uranium ion in batch mode using the native biomass as a control system. The uranium ion adsorption was also characterized by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectra, zeta potential analysis, and surface area measurement studies. The effects of pH, biomass amount, contact time, initial uranium ion concentration, and ionic strength were evaluated by using native and modified algal biomass preparations. The uranium ion removal was rapid, with more than 70 % of total adsorption taking place in 40 min, and equilibrium was established within 60 min. From the experimental data, it was found that the amount of adsorption uranium ion on the algal preparations decreased in the following series: amidoxime-modified algal biomass > PEI-modified algal biomass > native algal biomass. Maximum adsorption capacities of amidoxime- and PEI-modified, and native algal biomasses were found to be 366.8, 279.5, and 194.6 mg/g, respectively, in batchwise studies. The adsorption rate of U(VI) ion by amidoxime-modified algal biomass was higher than those of the native and PEI-modified counterparts. The adsorption processes on all the algal biomass preparations followed by the Dubinin-Radushkevitch (D-R) and Temkin isotherms and pseudo-second-order kinetic models. The thermodynamic parameters were determined at four different temperatures (i.e., 15, 25, 35, and 45 °C) using the thermodynamics constant of the Temkin isotherm model. The ΔH° and ΔG° values of U(VI) ion adsorption on algal preparations show endothermic heat of adsorption; higher temperatures favor the process. The native and modified algal biomass preparations were regenerated using 10 mM HNO3. These results show that amidoxime-modified algal biomass can be a potential candidate for effective removal of U(VI) ion from aqueous solution.
The agricultural residuals buckwheat hulls in the region of Jiaodong, China (BHJC) were employed to adsorb Au(III) ions both in the spiked samples and the gold-plating wastewater samples, and the relevant adsorption kinetics and isotherms were investigated. The investigation on the adsorption selectivity showed that BHJC displayed strong affinity for gold in the aqueous solutions. Furthermore, the process optimization was performed using response surface methodology (RSM), the quantitative relationship between the gold uptake and the different levels of experimental factors was used to work out optimized levels of these parameters.
We report on the efficient adsorption of gold ions from aqueous systems with thioamide-group chelating nanofiber membranes. The obtained membranes were prepared by a combination of chemical modification and electrospinning process. It was found that the maximum adsorption capacities of the chelating nanofibers toward Au(III) ions were 15.86 mmol/g, 23.50 mmol/g and 34.60 mmol/g, when the temperature was 298, 323 and 348 K, respectively. The nanofibers display a high adsorption efficiency for Au(III) ions. The Langmuir adsorption isotherm was applied to describe the adsorption processes. Kinetics of the Au(III) ions adsorption was found to follow pseudo-second-order rate equation. Furthermore, the as-prepared thioamide-group chelating nanofiber membranes, as well as Au(III) ions adsorbed nanofiber membranes, were carefully examined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). Based on the characterization results, a possible mechanism of Au(III) ions adsorption with the thioamide-group chelating nanofiber membranes was proposed. This study provides a promising nanofiber adsorbent with high and efficient adsorption property for heavy metal ions removal.
Chemical activation of sugarcane bagasse was carried out to produce adsorbents for gold recovery from aqueous solutions. The impregnation ratio with the activating agents (H3PO4 and ZnCl2) and the temperature of activation were of the most determining factors on the adsorbents’ properties. Under the optimal production conditions, H3PO4 and ZnCl2 led to the adsorbents with the surface areas of 970 and 1300 m2/g, and the maximum monolayer gold adsorption capacities of 324 and 291 mg Au/g adsorbent, respectively. The recovery of gold from the bagasse-based adsorbents was performed by the incineration method efficiently. Considering the low cost and availability of bagasse as the primary material, the method was economically affordable.
Rapid and selective gold (Au(III)) recognition and recovery was investigated by a new type mesoporous adsorbent. The adsorbent was prepared by direct immobilization of 3-(3-(methoxycarbonyl) benzylidene)hydrazinyl)benzoic acid (MBHB) onto highly ordered mesoporous silica monoliths. The adsorbent enhanced the color formation by stable complexation as [Au(III)-MBHB]n+ complexes during recognition and adsorption operations. The several influence factors such as solution acidity, color optimization in recognition system, Au(III) adsorption capacity of the adsorbent, competing metal ions effect and Au(III) extraction/recovery behaviour were systematically studied. The effective pH for Au(III) ions recognition and adsorption was 2.0 and the maximum adsorption capacity of the adsorbent was as high as 177.94 mg/g. In addition, the simultaneous Au(III) recognition and recovery from simulated urban mining solution was investigated. The data revealed that the recognition system was in a one-step and, even ultra-trace Au(III) concentrations without using highly sophisticated instruments implied the adsorbent was novel. The adsorbed Au(III) was extracted and recovered as pure Au(III) in a two-step elution process. After extraction, the adsorbent was regenerated simultaneously and found selective to Au(III) exhibiting the same capturing capacity as fresh adsorbent after rinsing with water. Performance of the regenerated adsorbent was checked and it was found that the adsorbent can be used up to seven reuse cycles. The selectivity experiments indicated that adsorbent possessed excellent recognition and adsorption property to
Au(III) ions, offering potential applications in recovery of Au(III) from multi-ionic aqueous systems.
The equilibrium constant K in the Langmuir isotherm is usually used to calculate the standard Gibbs free energy of adsorption (Delta G degrees). However, in a strictly theoretical sense, this calculation method is incorrect. The reason is that the K in the Langmuir isotherm has a dimension. According to the provisions of the International Union of Pure and Applied Chemistry (IUPAC), the standard equilibrium constant (K degrees) for calculating Delta G degrees must be a dimensionless parameter. We examined four examples from the literature and found that the calculation of Delta G degrees presented in these four references was incorrect. Based on the fact that this misapplication is very common, this note reviews the related literature and gives a short comment on this problem. Two methods for calculating the thermodynamic equilibrium constant by the Langmuir equation are provided and discussed.
A typical nanoporous-geomaterial (halloysite nanotubes, HNTs) was functionalized by polyethyleneimine (PEI) grafting and the functionalized halloysite (PEI-HNTs) exhibited excellent performance for Cr (VI) removal from aqueous solution and immobilization by reduction. After PEI modification, the Cr (VI) uptake capacity of PEI-HNTs was about 64 times higher than that of the original HNTs and the maximum equilibrium removal capacity was found to be 102.5 mg g−1 at 328 K. Part of Cr (VI) was reduced to Cr (III) and then precipitated on the surface of adsorbent during the sorption process as determined by X-ray photoelectron spectroscopic analysis, suggesting that the PEI-HNTs are not only useful for Cr (VI) immobilization but also good for its reduction. The adsorption of Cr (VI) by the PEI-HNTs was fitted to Langmuir model and the kinetics of uptake could be described by a pseudo-second-order rate model very well. The results also demonstrated that PEI-HNTs could detoxify Cr (VI) at low pH value. The mechanism of uptake of Cr (VI) was postulated to be electrostatic interaction followed by its immobilization through reduction. The functionalized nano-geomaterial synthesized here could be a promising candidate of low cost for highly efficient Cr (VI) removal followed by its immobilization.
To meet the global challenges of elemental sustainability a holistic approach to the extraction, use and recovery of precious and critical metals must be developed. Biosorption is a key technology for the benign recovery of diffuse elements from liquid effluents and hydrometallurgy processes. There is the opportunity to go beyond the remediation of heavy metals and pollutants, by utilising biosorption within a circular economy approach for the cycling of precious and critical metals in higher-value applications. This review provides an overview of the current research in the area of critical and precious metals recovery using biosorption, its application to real-life wastes and the potential uses for these metal-loaded materials for catalysis or functional materials.
The aim of the study was to develop green techniques to recover precious gold by the taurine-modified cellulose (TDAC samples) from the aqueous solution. Adsorption, followed by reduction offered a method for the recovery of ionic and zerovalent gold. The spherical gold nanoparticles (5 nm average size) were investigated in the nanoparticle-embedded gel. Potential rate controlling steps of chemical reactions are modeled by the best-fit of thermodynamic (an endothermic process), kinetic curve (pseudo second order), and isotherm (Sips and 34.5 mg/g Langmuir adsorption capacity) parameters. The pH (2–6) and competing heavy metals (Cd, Co, Cr, Ni, and As) showed least interference, however, gold recovery altered at the high ionic strength (as NaCl). A complexing agent (acidic thiourea) desorbed 86% of ionic gold and pyro-crystallization technique yielded 90% metallic gold. The characterization including X-ray photoelectron spectroscopy detected metallic gold on the surface of TDAC, supporting the adsorptive–reduction mechanism. Performance characteristic of TDAC to concentrate gold in various forms can be viewed as a controllable technique in the water treatment applications.
A biomass waste of microalgae was chemically modified by immobilizing the functional group of polyethyleneimine to prepare a new type of adsorbent. The adsorption test revealed that this adsorbent exhibited remarkably high selectivity for Pd(II) and Pt(IV) over base metal ions in HCl solution. From the adsorption isotherm, its maximum adsorption capacity for Pd(II) and Pt(IV) was evaluated as 2.0 and 0.8 mmol/g, respectively. This adsorbent also exhibited high affinity and selectivity for Pd(II) and Pt(IV) even in the presence of high concentrations of base metals in actual leach liquor.Present address for Kanjana Khunathai, Research Laboratories, DENSO CORPORATION, 500-1 Minamiyama, Komenoki, Nisshin, Aichi 470-0111, Japan
... 40 mg of PS-APD was placed in a 100 mL iodine flask, then 2 mL of Au ( III ) with ... 2, the pores between 30 and 70 nm were dominant for both resins . ... was swollen more completely at higher temperature, which made metal ions diffuse more easily into the inside of resin ; (2) the ...
Generation of geothermal energy is associated with a significant amount of geothermal fluids, which may be abundant in high-value metals, such as lithium, cesium, rubidium, and other precious and rare earth metals. The recovery of high-value metals from geothermal fluids would thus have both economic and environmental benefits. The conventional technologies applied to achieve this are mostly physicochemical, which may be energy intensive, pose the risk of secondary pollution whilst being inefficient in recovering metals from dilute solutions. Biological methods, based on biosorption or bioaccumulation, have recently emerged as alternative approaches, as they are more environmentally friendly, cost effective, and suitable for treating wastewater with dilute metal contents. This article provides a comprehensive review of the related biological technologies used to recover the high-value metals present in geothermal fluids as well as critical discussion on the key issues that are often used to evaluate the effectiveness of those methods.
Iron oxide nanoparticles are promising materials for many technological and environmental applications due to their versatile functionalization and magnetic properties that allow a facile remote control, separation and analyte recovery. In this contribution, the results of gold(III) sorption by naked and DMSA-capped (DMSA = m-2,3,dimercapto succinic acid) magnetite nanoparticles are discussed. Magnetite nanoparticles of 8 nm diameter were first synthesized by thermal decomposition of iron(III) oleate followed by a ligand exchange reaction to substitute oleic acid (OA) molecules by DMSA. Such systems of coated magnetite nanoparticles were characterized with Fourier transform infrared (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM) and magnetic measurements. FT-IR spectroscopy suggests that in Fe3O4@DMSA the organic coating is not homogeneous and it interacts with surface iron cations either through the carboxylate groups (by forming bridging bidentate complexes) or through disul
Biochar was modified as a high efficient and selective absorbent for copper ions (Cu(II)) by nitration and reduction. Results of X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) analyses indicated that the amino groups were chemically bound to the functional groups on the biochar surface. Kinetics, thermal dynamics, and adsorption and desorption of Cu(II) in fixed-bed were investigated. The results demonstrated that the amino-modified biochar exhibited excellent adsorption performance for Cu(II). The adsorption capacity and bed volume of the modified biochar are five- and eight- folds of the pristine biochar, respectively. The Cu(II) combined with the amino groups through strong complexation based on the comparison of XPS and ATR-FTIR analyses before and after adsorption, which endows it with the high pH stability and ion selectivity.
A tannin-based novel adsorbent, named “BTU-PT gel”, was prepared by immobilizing bisthiourea (BTU) ligand
on persimmon tannin (PT) extract. The adsorption behaviors of precious metal ions along with other coexisting base metal ions
onto BTU-PT gel were studied by batch and continuous column methods. The gel exhibited remarkable selectivity for precious
metal ions such as Au(III), Pd(II), and Pt(IV) over base metal ions such as Cu(II), Fe(III), Ni(II), and Zn(II) in 1−5 mol dm−3
hydrochloric acid. The adsorption of precious metal ions on the present gel was found to obey the typical monolayer type of
Langmuir model, and the maximum adsorption capacity of the adsorbent was evaluated as 5.18 mol kg−1 for Au(III), 1.80 mol
kg−1 for Pd(II), and 0.67 mol kg−1 for Pt(IV). Combination of ion exchange, electrostatic interaction, and coordination through
the thiocarbonyl group is the mechanism of adsorption of precious metals on BTU-PT gel. In the case of Au(III) adsorption, the
adsorbed species was simultaneously reduced to elemental gold by abundant polyphenolic groups of the tannin matrix. Elution by
using acidothiourea solution in continuous column experiment recovered the adsorbed precious metals almost quantitatively.
The results of a potential reusability test of the gel for consecutive adsorption and elution cycles by continuous column
experiment indicated that the gel was stable and regenerated with undiminished metal uptake capacity up to five cycles. The real
time applicability of the adsorbent for the recovery of precious metals from real industrial liquor was evaluated from actual acidic
leach liquor of printed circuit boards of spent mobile phones. The gel selectively adsorbed precious metal species but exhibited
negligible affinity toward base metals present in the leach liquor. The BTU-PT gel is a potential adsorbent for selective recovery
of precious metals from acidic leachate of spent mobile phones containing elevated concentrations of base metals
In the present work, a new 1,8-diaminonaphthalene-formaldehyde (1,8-DAN-F) polymer was synthesized by the reaction of 1,8-DAN with formaldehyde solution. The structure of 1,8-DAN-F polymer was characterized by elemental analysis, FT-IR spectroscopy and thermal analysis. In order to prepare a useful adsorbent, 1,8-DAN-F polymer was blended at the ratio of 25% with polyvinylchloride (PVC) using THF solvent. 1,8-DAN-F/PVC polymer blend was used in selective separation and recovery of Au(III) ions from Fe(III), Cu(II) and Ni(II) ions. The effects of pH and the initial concentration of Au(III) ions on the adsorption were examined by the batch technique. The optimum pH level was found to be 1 for the Au(III) adsorption. Furthermore, the adsorption data were applied to the Langmuir and Freundlich isotherms. It was found that the adsorption data fitted well to the Langmuir isotherm. The maximum Au(III) adsorption capacity (qmax) of the polymer blend was 119.0 mg·g− 1. The adsorption kinetics indicated that the Au(III) adsorption proceeds according to the pseudo-second-order model. Also, the separation of Au(III) ions from Fe(III), Cu(II) and Ni(II) ions was examined by the column technique. The column studies showed that Au(III) ions can be separated and concentrated from the base metal ions.
The aim of this study is to develop a polyethylenimine (PEI) grafted magnetic porous adsorbent for highly effective adsorption of heavy metals. The process of grafting PEI was confirmed by Fourier transform infrared (FTIR) analysis. Batch tests were carried out to investigate the adsorption performance. Adsorption of Cu2+, Zn2+ and Cd2+ was dependent on pH and increasing the pH was favorable to metal ions removal. The adsorption equilibrium was reached within 10min and well described by pseudo-second-order model. The sorption isotherms of the adsorbent for these metals fitted well with Langmuir model, with maximum adsorption capacities of 157.8, 138.8 and 105.2mg/g for Cu2+, Zn2+ and Cd2+, respectively. Competitive adsorption among the three metal ions showed a preferential adsorption of Cu2+>Zn2+>Cd2+. The magnetic adsorbent exhibited excellent acid–alkali stability. In addition, the exhausted adsorbent can be regenerated by 0.02mol/L EDTA solution without significant adsorption capacity loss.
a b s t r a c t The recovery of gold(III) ions from an aqueous solution onto a durio zibethinus husk (DZH) was examined after varying pH, contact time, adsorbent dosage, initial Au(III) concentration, and temperature. The func-tional groups of DZH were analyzed by FTIR and Au(III) recovery onto DZH was verified by FESEM–EDX and XRD analysis. Adsorption equilibrium isotherms and kinetics of the DZH were studied using Freundlich and Langmuir models, as well as pseudo first-order, second-order kinetic and intraparticle diffusion equa-tions. The experimental data obtained with DZH fitted best to the Langmuir isotherm model and exhibited a maximum adsorption capacity (q max) of 1724 mol g −1 . The data followed the pseudo second-order equation. The activation energy of the adsorption (E a) was estimated to be 38.5 kJ mol −1 . Thermodynamic parameters, such as changes in enthalpy, entropy and Gibbs free energy, showed that the adsorption is exothermic, spontaneous at low temperature, and is a chemisorption process. These results indicate that DZH adsorbs efficiently and could be used as a low-cost alternative for the adsorption of Au(III) in wastewater treatment. Crown Copyright © 2011 Published by Elsevier B.V. All rights reserved.
The synthesis of several coordinating polymers by grafting thiourea functional groups onto commercial macroporous polystyrene polymer matrices are described. In this paper, we also report the study on the absorption and elution of precious metal ions (or together with base metal ions, Cu2+ and Fe3+) from acidic chloride solutions. The results showed that these resins have appreciable capacity and good selectivity for the absorption of gold from acidic solutions. The extraction kinetics of the resins is slower than the corresponding monomolecular ‘free’ extractant analogues. However, some of the resins show acceptable extraction rates.
A new kind of nitrogen-doped graphene/carbon nanotube nanocomposite can be synthesized by a facile hydrothermal process under mild conditions, which exhibits synergistically enhanced electrochemical activity for the oxygen reduction reaction. This research provides a new route to access a metal-free electrocatalyst with a high activity under mild conditions.
Novel guanidylated hollow fiber membranes are prepared based on brominated poly (2,6-dimethyl-1,4-phenylene oxide) (BPPO) under mild reaction conditions. 1H-pyrazole-1-carboxamidine hydrochloride (HPCA) is employed for the guanidylation in aqueous solution at room temperature. The obtained guanidylated PPO hollow fiber membranes (GPPO HFMs) contain 0.31-0.95mmol/g guanidyl groups and show high affinity to tetrachloroauric anions (AuCl(4)(-)) in acid solutions. For 0.1M HCl solution containing 57.8mg gold/L, the sorption amount can get as high as 130mg/g. Besides, the GPPO HFMs show preferable selectivity toward gold in multicomponent solution containing Mg(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and Pb(II). A system of comparison experiments involving the sorption behavior of GPPO HFMs and quaternary aminated HFMs are also performed. The results reveal that driving forces for the high adsorption of gold mainly involve complexation mechanism. Overall, the obtained GPPO HFM is a promising chelating material for the recovery of gold.
The recovery of copper, lead and tin from scrap printed circuit boards (PCBs) has been achieved using a combination of leaching, electrochemical ion exchange and electrodeposition. A simple aqueous nitric acid stripping solution, with the concentration range of 1–6 mol dm ⁻³ , has demonstrated the potential for selective extraction of copper and lead from the PCBs. Precipitation of tin as H 2 SnO 3 (metastannic acid) occurred at acid concentrations above 4 mol dm ⁻³ . Preliminary galvanostatic electrolysis from simulated leaching solutions has investigated the feasibility of electrodeposition of copper and lead at different concentrations of HNO 3 . Cathodic lead deposition, particularly at high electrolyte conditions, resulted in poor current efficiency. This was mainly due to dentritic metal formation and subsequent re‐dissolution. An alternative method investigated for recovering the metal values was the simultaneous electrodeposition of copper at the cathode and lead dioxide at the anode. Electrohydrolysis for acid and base regeneration from the spent nitric acid electrolyte has also been investigated.
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