Empty fruit bunch (EFB) from oil palm is one of the potential biomass to produce biofuels like bio-oil due to its abundant supply and favorable physicochemical characteristics. Confirming the ...assertion, this paper presents an overview of EFB as a feedstock for bio-oil production. The fundamental characteristics of EFB in terms of proximate analysis, ultimate analysis and chemical composition, as well as the recent advances in EFB conversion processes for bio-oil production like pyrolysis and solvolysis are outlined and discussed. A comparison of properties in terms of proximate analysis, ultimate analysis and fuel properties between the bio-oil from EFB and petroleum fuel oil is included. The major challenges and future prospects towards the utilization of EFB as a useful resource for bio-oil production are also addressed.
•Palm EFB has high heating value and low greenhouse gas emissions during combustion.•Conversion of EFB to bio-oil is mainly by fast pyrolysis without and with catalyst.•Bio-oil from EFB is lower in heating value, heavier and more acidic than fuel oil.•The viscosity of bio-oil from EFB is between those of light and heavy fuel oils.•The flash and pour points of bio-oil from EFB are close to those of light fuel oil.
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•Deacetylation degree and molecular weight of raw chitosan affect metal sorption.•Raw chitosan was modified physically, chemically and characterized mainly by FTIR.•Modified chitosan ...outshined raw chitosan in Au(III) sorption capacity and selectivity.•Au(III) sorption by modified chitosan complied with Langmuir and was spontaneous.•Modified chitosan adsorbed Au(III) by mixed mechanisms and showed good reusability.
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.
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.
Bio-oil is a potential biofuel for fossil fuel substitution due to its great versatility in feedstock and environmental benefits. In particular, bio-oil derived from palm empty fruit bunches (PEFB) ...has drawn considerable research attention in recent years owing to the abundant supply of PEFB and the emergence of motivation to turn waste into wealth for environmental sustainability. Therefore, this paper aims to provide a state-of-the-art review on the bio-oil derived from PEFB. A particular emphasis is placed on the optimum production conditions of PEFB-derived bio-oil by various fast pyrolysis and liquefaction processes, as well as on the characteristics of PEFB-derived bio-oil in terms of their physicochemical properties, major chemical components and their compositions. A comparison of physicochemical properties of PEFB-derived bio-oil with those of other biomass-derived bio-oil and petroleum fuel oil is also outlined. Upgrading of PEFB-derived bio-oil by different methods along with its fuel applications and future prospects are also discussed.
•PEFB-derived bio-oil is produced mostly by fast pyrolysis and liquefaction.•Catalyst, PEFB pretreatment and/or solvent used affect the bio-oil characteristics.•PEFB-derived bio-oil is scarcely researched compared to wood-derived bio-oil.•PEFB-derived bio-oil has been upgraded by many methods but further study is needed.•Limited fuel application of PEFB-derived bio-oil is due to its quality deficiency.
Rice husk is a prospective bio-oil feedstock due to its plentiful supply, but its unfavorable characteristics like high moisture content, high ash content, and low energy density tend to jeopardize ...both the yield and quality of bio-oil produced by fast pyrolysis. Lately, various pretreatments, namely, washing, torrefaction (dry and wet), and their combined pretreatments, have been researched on rice husk with the aim of improving its unfavorable characteristics for bio-oil production. However, the influences of different pretreatments on pretreated rice husk and the subsequent bio-oil produced have not been compared. Hence, this review paper presents an overview of rice husk as a bio-oil feedstock and its pretreatment methods for bio-oil production via fast pyrolysis. Particular emphasis is placed on the rice husk characteristics and their impacts on the bio-oil production via fast pyrolysis, as well as the different types of rice husk pretreatment and their influences on the characteristics of pretreated rice husk, product yields of fast pyrolysis, and the composition and physical properties of the bio-oil produced. A comparison of the physicochemical properties of rice husk- and other biomass-based bio-oil alongside those of petroleum fuel oil is also outlined. Major challenges and future prospects towards the utilization of rice husk as a bio-oil feedstock and the integration of rice husk pretreatment with fast pyrolysis for large-scale applications are also discussed.
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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.
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.
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•LDPE, HDPE, PP, and PS are more promising than PVC and PET as pyrolysis feedstock.•Low to moderate temperature, heating rate, and residence time favor plastic oil.•Lower pressure, smaller particle size and reactive gas atmosphere favor plastic oil.•Catalysts usually promote better plastic oil quality but do not necessarily yield.•Plastic oil is fit for fossil fuel blending/replacement due to its good properties.
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•Efficiency of WVCLM was affected by all factors except for stripping phase flow rate.•At 500mg/L initial Cu2+, WVCLM achieved peak extraction of 96% and stripping of 80%.•WVCLM was ...deemed viable considering the use of green and cheap waste vegetable oil.
Separation of Cu(II) ions from aqueous solutions using an innovative waste vegetable oil-based continuous liquid membrane (WVCLM) was studied with waste vegetable oil as diluent, di-2-ethylhexylphosphoric acid (D2EHPA) as carrier and sulphuric acid (H2SO4) as stripping phase. For an initial Cu(II) ion concentration of 500mg/L, the maximum percentages of extraction (96%) and stripping (80%) were achieved in 8h and 24h, respectively, with feed phase buffered at pH 4.5, 250mM of inert salt, 88mM of D2EHPA, 1.5M of H2SO4, 2.5L/h of membrane phase, 4.0L/h of feed phase and 0L/h of stripping phase.
Solvent extraction of Cu(II) from aqueous solutions by a soybean oil-based organic solvent (SOS) composing of soybean oil (diluent), di-2-ethylhexylphosphoric acid (extractant) and tributylphosphate ...(phase modifier) was investigated. Effects of initial Cu(II) concentration in the aqueous phase (25–500
mg/L (0.39–7.88
mM)) and temperature (298–323
K) on the percentage extraction (%
E) of Cu(II) were studied. It was found that the initial Cu(II) concentration did not influence %
E appreciably and high %
E (>98%) was achieved throughout the experimental ranges studied. The %
E at various temperatures, on the other hand, decreased consistently with temperature. The loading capacity of SOS (2400
mg/L (37.82
mM)), as well as the stoichiometry (4:1) and structure (inner sphere) of Cu(II)–organic complexes (extracted species) in SOS were also determined. Stripping of Cu(II) from the loaded SOS was investigated with various types (sulfuric acid (H
2SO
4), hydrochloric acid (HCl) and nitric acid (HNO
3)) and concentrations (0.05–2.00
M) of mineral acids. The decreasing order of percentage stripping (%
S) of Cu(II) by various types of acids was found to be H
2SO
4
>
HCl
>
HNO
3 throughout different concentrations studied, with H
2SO
4 attaining the highest %
S (>99%) at 1.5
M.
