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•Comparison between non-metal doping and metal-doping of carbon quantum dots.•Nitrogen and bismuth doping tune the photoluminescence properties of rice husk-derived carbon quantum ...dots (RHCQDs).•N-RHCQDs (10 vol%) and Bi-RHCQDs (5 wt%) are the best samples from the degradation of methylene blue and copper (II) removal.•Doped RHCQDs give MB degradation performance up to around 70% and Cu (II) removal performance up to more than 50%.
In this study, heteroatoms doped carbon quantum dots were synthesized using rice husk as a biowaste precursor. The effects of nitrogen and bismuth doping are investigated by adjusting the amount of ethylenediamine (EDA) as the nitrogen source, and bismuth nitrate pentahydrate as the bismuth source. HRTEM analysis depicted the formation of spherical carbon quantum dots, with a size of less than 10 nm. FTIR and XPS analysis confirmed the presence of essential functional groups and chemical composition in both of the doped carbon quantum dots. UV–Vis spectra showed peaks which are associated to the electronic transition of the C = C bonding. The addition of EDA and bismuth nitrate pentahydrate tuned the fluorescence intensity and shifted the emission wavelength from the blue region to green one. The performance of the doped rice husk derived carbon quantum dots (RHCQDs) was evaluated via photodegradation of the methylene blue (MB), under a 300 W Xenon lamp. as well as via copper (II) removal. N-RHCQDs (10 vol%) and Bi-RHCQDs (5 wt%) demonstrated the highest MB degradation performance, at 72.16% and 68.91%, respectively. The degradation of MB of the two doped RHCQDs fitted with the pseudo-second kinetic model. The doped RHCQDs were then tested for copper (II) removal, obtaining removal performance of 56.23% and 33.13%, respectively. The results suggest that the Cu (II) adsorption onto the N-RHCQDs and Bi-RHCQDs agrees with the pseudo-second kinetic model and the Langmuir isotherm, with maximum adsorption capacity of 5.73 and 4.08 mg/g, respectively.
Summary
Carbon capture and storage (CCS) technologies have gained global attention due to the environmental impact caused by CO2. Ionic liquid, also known as a designer solvent, has good potential ...for CO2 capture application due to its good CO2 affinity, negligible vapor pressure and high thermal stability. The combination of ionic liquid and membrane technology has been introduced for the more effective use of ionic liquid. This review offers a comprehensive overview of mixed matrix membrane (MMM) and the application of ionic liquid in the membrane for CO2 separation, focusing on recent advances in ionic liquid‐based MMM. Descriptions of various MMM modification strategies using ionic liquid and the influence of challenging operating conditions on the CO2 separation performance of ionic liquid‐based MMM are discussed.
Ionic liquid has good potential for CO2 capture application due to its good CO2 affinity, negligible vapor pressure, and high thermal stability.
The combination of ionic liquid and membrane technology has been introduced for the more effective use of ionic liquid.
This review offers a comprehensive overview of mixed matrix membrane and the application of ionic liquid in the membrane for CO2 separation, focusing on recent advances in ionic liquid‐based mixed matrix membrane.
In the present work, palm kernel shell (PKS) biomass waste has been used as a low-cost and easily available precursor to prepare carbon dots (CDs) via microwave irradiation method. The impacts of the ...reacting medium: water and diethylene glycol (DEG), and irradiation period, as well as the presence of chitosan on the CDs properties, have been investigated. The synthesized CDs were characterized by several physical and optical analyses. The performance of the CDs in terms of bacteria cell imaging and copper (II) ions sensing and removal were also explored. All the CDs possessed a size of 6-7 nm in diameter and the presence of hydroxyl and alkene functional groups indicated the successful transformation of PKS into CDs with carbon core consisting of C = C elementary unit. The highest quantum yield (44.0%) obtained was from the CDs synthesised with DEG as the reacting medium at irradiation period of 1 min. It was postulated that the high boiling point of DEG resulted in a complete carbonisation of PKS into CDs. Subsequently, the absorbance intensity and photoluminescence intensity were also much higher compared to other precursor formulation. All the CDs fluoresced in the bacteria culture, and fluorescence quenching occurred in the presence of heavy metal ions. These showed the potential of CDs synthesised from PKS could be used for cellular imaging and detection as well as removal of heavy metal ions.
Waste cooking oil (WCO) appears to be a potential carbonaceous source for synthesizing graphene sand composite (GSC) adsorbent in removing pollutants. This study presents a green synthesis method of ...GSC using WCO as a sustainable carbon source for the synthesis of GSC through the thermal graphitization method. Characterization analysis conducted on GSC
verified the successful coating of WCO onto the sand surface and conversion to graphene, which possessed distinct functional groups and features of graphene materials. GSC
adsorbent effectiveness in removing Congo Red dye through batch adsorption was studied under the influence of different initial concentrations (20 to 100 mg/L), and the optimum pH (pH 2 to 10), contact time (5 to 240 min), and temperature (25 to 45 °C) were investigated. The GSC
showed removal rates of 91.5% achieved at an initial dye concentration of 20 mg L
, 1.0 g of adsorbent dosage, a temperature of 25 °C, and 150 min of contact time. The GSC
exhibited a maximum capacity of 5.52 mg g
, was well-fitted to the Freundlich isotherm model with an R
value of 0.989 and had an adsorption mechanism that followed the pseudo-second-order kinetic model. Negative values of enthalpy (ΔH) and Gibbs free energy (ΔG) revealed that CR adsorption onto GSC
was a spontaneous and exothermic process. The presence of functional groups on the surface of GSC
with such interactions (π-π attractive forces, hydrophobic forces, and hydrogen bonding) was responsible for the anionic dye removal. Regeneration of GSC
adsorbent declined after four cycles, possibly due to the chemisorption of dyes with GSC that resulted in inefficient adsorption. Being a waste-to-wealth product, GSC
possessed great potential to be used for water treatment and simultaneously benefited the environment through the effort to reduce the excessive discharge of WCO.
Abstract
In this study, hematite graphene oxide (αFe
2
O
3
-GO) powder nanocomposites and thin-film hematite graphene oxide (αFe
2
O
3
-GO) were synthesized for application in the removal of ...Rhodamine B (RhB) from textile wastewater. αFe
2
O
3
-GO nanomaterials were placed onto the FTO substrate to form a thin layer of nanocomposites. Different analysis including XRD, FTIR, Raman spectra, XPS, and FESEM were done to analyze the morphology, structure, and properties of the synthesized composites as well as the chemical interactions of αFe
2
O
3
with GO. The photocatalytic performance of two synthesized composites was compared with different concentrations of αFe
2
O
3
-GO. The results showed that powder nanocomposites are more effective than thin-film composites for the removal of RhB dye. αFe
2
O
3
-GO-5% powder nanocomposites removed over 64% of dye while thin-film nanocomposites had less removal efficiencies with just under 47% removal rate. The reusability test was done for both materials in which αFe
2
O
3
-GO-5% powder nanocomposites removed a higher rate of dye (up to 63%) in more cycles (6 cycles).
A life cycle assessment of anaerobic-treated palm oil mill effluent (POME) was conducted to assess the environmental performance on two integrated treatment processes: the typical hollow fiber ...membrane ultrafiltration module coupled with adsorption and electro-oxidation as pretreatment. The analysis was undertaken using the ReCiPe 2016 method and SimaPro v9 software was employed using a 'cradle-to-gate' approach. The results showed that hollow fiber membrane from the adsorption integrated membrane impacted significantly at 42% to 99% across all impact categories for both processes. Overall, the electro-oxidation integrated membrane was discovered to have a lesser environmental impact, particularly on the ozone formation (human health) (HOFP) at 0.38 kg NOx-eq in comparison to the adsorption integrated membrane at 0.66 kg NOx-eq. The total characterization factor of the endpoint category for human health is 8.61 × 10
DALY (adsorption integrated membrane) and 8.45 × 10
DALY (electro-oxidation integrated membrane). As membrane treatment is closely linked to energy consumption, the environmental impact with different sources of energy was evaluated for both processes with the impacts decreasing in the following order: Grid > Biogas > Grid/Solar. Future research should concentrate on determining the overall 'cradle-to-grave' environmental impact of treating POME, as well as other scenarios involving membrane treatment energy utilization using LCA. This study can help decision-makers in identifying an environmentally sustainable POME treatment and management, especially in Malaysia.
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•Bright blue fluorescence CDs were synthesized from palm kernel shell biomass.•Formation mechanism of CDs was successfully deduced based on TEM images.•CDs possessed the potential to ...be used for cell imaging of B. subtilis and E. coli.•Fluorescence quenching of CDs indicated potential as metal ions sensing material.•Photo stability and consistency of CDs towards different conditions was verified.
The present study systematically investigated the influence of synthesis conditions (duration, reaction medium, and doping concentration) and formation mechanism of carbon dots (CDs) derived from low-cost and abundant biomass palm kernel shell (PKS). Surprisingly, the dopant (urea) did not enhance the photoluminescence of CDs as expected, which could be attributed to the low reactivity between the dopant and PKS macromolecules. Variation of synthesis duration from 30 to 120 s clearly indicated the formation mechanism of CDs, involving the stages of dehydration, carbonization, and nucleation. The CDs with the highest photoluminescent intensity and quantum yield was obtained at synthesis duration of 90 s, aligned well with the perfect spherical shape of CDs and the synergistic effects of both surface and carbogenic core conditions. Understanding the formation mechanism could be used to optimize the synthesis of CDs, and hence linked to quantum yield and fluorescent intensity. In terms of application potential, the CDs illuminated well as fluorescent ink and in bacteria cells imaging. The potential of CDs as sensing material has also been proven with the quenching of fluorescence in the presence of metal ions. The linear range for detection of Cu2+ ions was 0.1–0.5 mM with a detection limit as low as 0.05 mM. This signifies the potential of CDs fabricated from PKS as a low-cost and easily available material for Cu2+ ions detection in aqueous solution. The CDs possessed reasonable photo stability as indicated by its consistent fluorescence level even after exposure to UV radiation for a prolonged period of 180 minutes. Overall, a simple, straightforward, and fast method is developed to synthesis strong blue emissive CDs from green PKS that are potentially suitable for Cu2+ ions sensing in real application.
Pro-environmental behaviour is imperative to promote sustainable management and consumption of energy in the fight against climate change. The Theory of Planned Behaviour (TPB) has been widely used ...to explain and predict behaviour in a multitude of behavioural domains including pro-environmental behaviour. However, the TPB does not prioritise the influence of knowledge and habits on pro-environmental behaviour. Past studies also confirmed the influence of cultural factors in predicting environmental intent and behaviour, which were not covered by TPB. Considering that Malaysia is a multicultural country, on top of the environmental education factors, cognitive competencies, and affective factors, the influence of values that contribute to the pro-environmental intention behaviour on energy conservation has also to be considered. Hence, this study employed Fuzzy Delphi Method to determine the indicators explaining the effects of educational and psychological factors on pro-environmental behaviour. It was hypothesized that educational factors, cognitive competencies and affective factors influence secondary students' pro-environmental behaviour on energy conservation. The students' cultural viewpoint was also proposed as the regulating effect on their energy conservation behaviour. A total of 25 experts were selected to validate the questionnaire developed. The items/constructs developed were environmental factors (formal, non-formal and informal educations), cognitive factors, affective factors (attitude, subjective norm, perceived behavioural control and civic values) and environmental conservation behaviour. The value construct, which comprised of values of empathy, respect, cooperation, responsibility, justice, equality, integrity, and altruism. Majority of the items/constructs were accepted by the experts. This reflects that the items/constructs developed were relevant to the study as the experts agreed with these items/constructs.
Natural coagulants have shown its coagulation efficiency as reported in a substantial number of research articles. However, the acceptance and widespread application of natural coagulants in water ...industry is still low. It is necessary to conduct a review to boost the potential of using natural coagulants by highlighting the current development and the efforts for improving the capability of natural coagulants, including showing the compatibility of natural coagulants with other treatment technologies in integrated/hybrid treatment process; the modification of natural coagulants for marked improvement in coagulation performance efficiency; the possibility of hybridizing natural coagulants with other types of coagulants; the improvement of extraction and purification approaches for high purity of natural coagulants; and the synthesis of multifunctional natural coagulants. Though the current progress of natural coagulants is quite encouraging, perspectives from sustainability assessment showed that the acceptance and commercialization of natural coagulants are hindered by two main challenges: practicality and feasibility of real field application and sustainability of using natural coagulants overlooking technical, environmental, economic, and social aspects. Future research focusing on these issues may help to clarify the uncertainties shrouded on natural coagulants and at the same time shifting the water industry to be more sustainable.
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•Natural coagulants have been extensively studied in water and wastewater treatment.•Widespread application of natural coagulants in the water industry is still low.•Latest development and improvement of natural coagulants have been reviewed.•Sustainability of natural coagulants was discussed from various perspectives.•Future research to clarify the uncertainty on natural coagulants was highlighted.
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