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1.
Int J Biol Macromol ; 252: 126491, 2023 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-37625756

RESUMO

This work aimed to develop a modified chitosan adsorbent with enhanced adsorption selectivity for Au(III) over Cu(II) from acidic chloride solutions using low-cost and green raw materials. Various adsorbents, i.e., chitosan powder, chitosan microbeads, chitosan/palm kernel fatty acid distillate (PKFAD) microcomposites, magnetite nanoparticles, and chitosan/PKFAD/magnetite nanocomposites (CPMNs), were first evaluated for their ability to adsorb Au(III) and Cu(II) from single- and binary-metal solutions across different pH levels, followed by parametric analysis of Au(III) and Cu(II) adsorption from binary- and multi-metal solutions onto CPMNs, Au(III) desorption from Au(III)-loaded CPMNs, and reusability of CPMNs. Finally, Au(III)-loaded CPMNs were characterized with SEM-EDX, XRD, FTIR, and XPS to confirm the proposed adsorption mechanisms. Among all the adsorbents studied, CPMNs exhibited outstanding performance in adsorbing Au(III) from an equimolar binary Au(III)-Cu(II) solution, achieving the highest equilibrium adsorption capacity of 0.479 mmol/g (94.4 mg/g) without reaching saturation. Under optimal adsorption conditions of pH 3, 1 g/L CPMN dosage, and 90 min contact time, CPMNs adsorbed 96 % of Au(III) with a selectivity over Cu(II) exceeding 99 %. CPMNs demonstrated excellent reusability, maintaining over 80 % adsorption and desorption efficiencies for 5 cycles. The proposed adsorption mechanisms of CPMNs for Au(III) encompass electrostatic attraction, hydrogen bonding, solvation, and reduction.


Assuntos
Quitosana , Nanocompostos , Poluentes Químicos da Água , Óxido Ferroso-Férrico , Quitosana/química , Adsorção , Cloretos , Cinética , Cobre/química , Nanocompostos/química , Ácidos Graxos , Concentração de Íons de Hidrogênio , Poluentes Químicos da Água/química , Soluções
2.
Sci Total Environ ; 877: 162719, 2023 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-36933741

RESUMO

Turning plastic waste into plastic oil by pyrolysis is one of the promising techniques to eradicate plastic waste pollution and accelerate the circular economy of plastic materials. Plastic waste is an attractive pyrolysis feedstock for plastic oil production owing to its favorable chemical properties of proximate analysis, ultimate analysis, and heating value other than its abundant availability. Despite the exponential growth of scientific output from 2015 to 2022, a vast majority of the current review articles cover the pyrolysis of plastic waste into a series of fuels and value-added products, and up-to-date reviews exclusively on plastic oil production from pyrolysis are relatively scarce. In light of this void in the current review articles, this review attempts to provide an up-to-date overview of plastic waste as pyrolysis feedstock for plastic oil production. A particular emphasis is placed on the common types of plastic as primary sources of plastic pollution, the characteristics (proximate analysis, ultimate analysis, hydrogen/carbon ratio, heating value, and degradation temperature) of various plastic wastes and their potential as pyrolysis feedstock, and the pyrolysis systems (reactor type and heating method) and conditions (temperature, heating rate, residence time, pressure, particle size, reaction atmosphere, catalyst and its operation modes, and single and mixed plastic wastes) used in plastic waste pyrolysis for plastic oil production. The characteristics of plastic oil from pyrolysis in terms of physical properties and chemical composition are also outlined and discussed. The major challenges and future prospects for the large-scale production of plastic oil from pyrolysis are also addressed.

3.
Carbohydr Polym ; 256: 117423, 2021 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-33483013

RESUMO

Chitosan, a prestigious versatile biopolymer, has recently received considerable attention as a promising biosorbent for recovering gold ions, mainly Au(III), from aqueous solutions, particularly in modified forms. Confirming the assertion, this paper provides an up-to-date overview of Au(III) recovery from aqueous solutions by raw (unmodified) and modified chitosan. A particular emphasis is placed on the raw chitosan and its synthesis from chitin, characteristics of raw chitosan and their effects on metal sorption, modifications of raw chitosan for Au(III) sorption, and characterization of raw chitosan before and after modifications for Au(III) sorption. Comparisons of the sorption (conditions, percentage, capacity, selectivity, isotherms, thermodynamics, kinetics, and mechanisms), desorption (agents and percentage), and reusable properties between raw and modified chitosan in Au(III) recovery from aqueous solutions are also outlined and discussed. The major challenges and future prospects towards the large-scale applications of modified chitosan in Au(III) recovery from aqueous solutions are also addressed.


Assuntos
Quitosana/química , Ouro/química , Ouro/isolamento & purificação , Adsorção , Biopolímeros/química , Quitina/química , Cromatografia por Troca Iônica , Concentração de Íons de Hidrogênio , Resíduos Industriais , Íons , Cinética , Reprodutibilidade dos Testes , Espectroscopia de Infravermelho com Transformada de Fourier , Termodinâmica , Água/química , Poluentes Químicos da Água/isolamento & purificação , Purificação da Água
4.
Environ Sci Pollut Res Int ; 27(26): 32371-32388, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32533493

RESUMO

Water pollution and depletion of natural resources have motivated the utilization of green organic solvents in solvent extraction (SX) and liquid membrane (LM) for sustainable wastewater treatment and resource recovery. SX is an old and established separation method, while LM, which combines both the solute removal and recovery processes of SX in a single unit, is a revolutionary separation technology. The organic solvents used for solute removal in SX and LM can be categorized into sole conventional, mixed conventional-green, and sole green organic solvents, whereas the stripping agents used for solute recovery include acids, bases, metal salts, and water. This review revealed that the performance of greener organic solvents (mixed conventional-green and sole green organic solvents) was on par with the sole conventional organic solvents. However, some green organic solvents may threaten food security, while others could be pricey. The distinctive extraction theories of various sole green organic solvents (free fatty acid-rich oils, triglyceride-rich oils, and deep eutectic solvents) affect their application suitability for a specific type of wastewater. Organic liquid wastes are among the optimal green organic solvents for SX and LM in consideration of their triple environmental, economic, and performance benefits.


Assuntos
Águas Residuárias , Água , Óleos de Plantas , Solventes
5.
J Environ Manage ; 92(10): 2580-5, 2011 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-21700383

RESUMO

This study aimed to identify the significant factors that give large effects on the efficiency of Cu(II) extraction from aqueous solutions by soybean oil-based organic solvents using fractional factorial design. Six factors (mixing time (t), di-2-ethylhexylphosphoric acid concentration ([D2EHPA]), organic to aqueous phase ratio (O:A), sodium sulfate concentration ([Na(2)SO(4)]), equilibrium pH (pH(eq)) and tributylphosphate concentration ([TBP])) affecting the percentage extraction (%E) of Cu(II) were investigated. A 2(6-1) fractional factorial design was applied and the results were analyzed statistically. The results show that only [D2EHPA], pH(eq) and their second-order interaction ([D2EHPA] × pH(eq)) influenced the %E significantly. Regression models for %E were developed and the adequacy of the reduced model was examined. The results of this study indicate that fractional factorial design is a useful tool for screening a large number of variables and reducing the number of experiments.


Assuntos
Cobre , Solventes , Óleo de Soja , Purificação da Água , Água/química , Análise de Variância , Concentração de Íons de Hidrogênio , Modelos Estatísticos , Ácidos Fosfóricos , Análise de Regressão , Soluções , Sulfatos
6.
J Hazard Mater ; 190(1-3): 197-204, 2011 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-21493005

RESUMO

The objectives of this work were to select suitable design parameters and optimize the operating parameters of a soybean oil-based bulk liquid membrane (BLM) for Cu(II) removal and recovery from aqueous solutions. The soybean oil-based BLM consists of an aqueous feed phase (Cu(II) source), an organic membrane phase (soybean oil (diluent), di-2-ethylhexylphosphoric acid (D2EHPA) (carrier) and tributylphosphate (phase modifier)) and an aqueous stripping phase (sulfuric acid solution (H(2)SO(4))). Effects of design parameters (stirring condition and stripping/membrane to feed/membrane interface area ratio) of soybean oil-based BLM on the Cu(II) removal and recovery from aqueous solutions were investigated and the suitable parameters were selected for further studies. Optimization of the operating parameters (D2EHPA concentration, H(2)SO(4) concentration, stirring speed, temperature and operating time) of soybean oil-based BLM for maximum percentage (%) recovery of Cu(II) was then conducted using Response Surface Methodology and the optimum parameters were determined. A regression model for % recovery was developed and its adequacy was evaluated. The experimental % recovery obtained under the optimum operating conditions was compared with the predicted one and they were found to agree satisfactorily with each other.


Assuntos
Cobre/isolamento & purificação , Membranas Artificiais , Óleo de Soja/química , Poluentes Químicos da Água/isolamento & purificação , Organofosfatos , Soluções
7.
J Hazard Mater ; 181(1-3): 868-72, 2010 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-20638965

RESUMO

Various types of vegetable oil-based organic solvents (VOS), i.e. vegetable oils (corn, canola, sunflower and soybean oils) with and without extractants (di-2-ethylhexylphosphoric acid (D2EHPA) and tributylphosphate (TBP)), were investigated into their potentiality as greener substitutes for the conventional petroleum-based organic solvents to extract Cu(II) from aqueous solutions. The pH-extraction isotherms of Cu(II) using various vegetable oils loaded with both D2EHPA and TBP were investigated and the percentage extraction (%E) of Cu(II) achieved by different types of VOS was determined. Vegetable oils without extractants and those loaded with TBP alone showed a poor extractability for Cu(II). Vegetable oils loaded with both D2EHPA and TBP were found to be the most effective VOS for Cu(II) extraction and, thus, are potential greener substitutes for the conventional petroleum-based organic solvents.


Assuntos
Cobre/isolamento & purificação , Óleos de Plantas , Solventes/química , Poluentes Químicos da Água/isolamento & purificação , Química Verde , Soluções
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