Role of graphene oxide in support layer modification of thin film composite (TFC) membrane for forward osmosis application

In this work, the effect of graphene oxide (GO) incorporation into the membrane support layer towards the performance of thin-film composite (TFC) membrane was investigated. The support layer was fabricated by phase inversion method with the incorporation of GO as hydrophilic nanoparticles. Next, the active polyamide layer was formed on the membrane support layer via interfacial polymerization between trimesoyl chloride (TMC) and m-Phenylenediamine (MPD). The cross-section images from Field-Emission Scanning Electron Microscope (FESEM) showed the presence of active polyamide layer on the surface of TFC membrane while the FTIR results indicated the existence of bands associated with the amide linkages. The initial study showed that an optimal amount of GO (0.5 wt%) incorporation into the polymer substrate resulted in favourable improvement in TFC membrane performance. The physical and chemical properties of GO helps in enhancing the water transport through the membrane polymer matrix and thus contributing to higher permeate flux. The TFC-FO membrane incorporated with GO showed 44% improvement in terms of water flux (3.72 compared to 2.09 Lm-2 h-1 for pure PSf membrane) and minimal improvement in reverse solute diffusion (0.02 compared to 0.03 g m-2 h-1 for pure PSf membrane). Thus, this study showed that small addition of GO nanoparticles into the membrane support layer leads to an increase in performance of TFC membrane for FO application

Energy comparison and cost estimation of pressure-retarded osmosis using spiral wound membrane

Advancements in Pressure Retarded Osmosis (PRO) technology are enhancing the feasibility of evaluating its economic viability against other renewable energy production methods. This is done using the Levelized Cost of Energy (LCOE) as a metric. The study focuses on three PRO scenarios designed to minimize environmental impact and promote sustainable energy. These scenarios utilize a spiral-wound membrane module combined with hyper-saline solutions from Reverse Osmosis (RO) and wastewater from demineralization processes. Experimental results using a commercial spiral-wound membrane in the PRO system yielded LCOE values of USD 0.0702/kWh for a draw solution (DS) concentration of 36.2 g/l, USD 0.0563/kWh for 44.2 g/l, and USD 0.0721/kWh for 51.8 g/l. The study also evaluated environmental viability by considering the cost of CO2 emissions. This comprehensive comparison highlighted PRO's competitiveness with fossil fuels, showing it to be a reasonable alternative to coal and oil but less practical than natural gas. Specifically, the environmental analysis revealed that PRO is approximately 25.2 % more competitive than coal and 9.76 % more competitive than oil but 27.16 % less competitive compared to natural gas in terms of CO2 emission costs. This underscores the importance of considering carbon emission mitigation in energy generation.</p

Factorial screening on the development of cellulose nanocrystal/ carboxylated multi-walled carbon nanotube polyethersulfone membrane for humic acid rejection

A two-level factorial experimental design was used to formulate the dope composition of cellulose nanocrystal (CNC) multi-walled carbon nanotube (MWCNT) polyethersulfone (PES) membrane for humic acid (HA) rejection. Four factors were screened, which are the composition of PES (1517 wt.%), polyvinylpyrrolidone (PVP, 1-4%), CNC (0.01-0.75%), and carboxylated MWCNT (00.025%). The membranes were evaluated based on HA rejection from a 10-ppm aqueous feed solution. The percentage of MWCNT was the most significant factor, accounting for 72.31 % of the contribution. The highest HA rejection of 90% was obtained from the membrane fabricated using 17 % PES, 1% PVP,0.01 % CNC, and 0.025% MWCNT. The predicted values generated from the model agreed reasonably with the experimental data, demonstrating the model's validity

Effect of cellulose nanocrystals and carboxylated multiwalled carbon nanotubes on performance of polyethersulfone membrane for humic acid removal

Persistent declines in flux due to membrane fouling result in decreased treated water production, higher energy consumption, and a frequent need for chemical cleaning. Carbon nanotubes-based membranes have shown remarkable separation capabilities in water treatment processes while being relatively resistant to biofouling. Cellulose-based membranes, on the other hand, have demonstrated outstanding biocompatibility and versatile surface chemistry. In the current study, a hybrid polyethersulfone (PES) membrane was synthesized by integrating with single cellulose nanocrystals (CNC), single carboxylated multiwalled carbon nanotubes (MWCNT), and a mixture of CNC and MWCNT utilizing the phase inversion method. This combination of nanomaterials was aimed at eliciting synergistic effects to enhance the overall membrane performance. The evaluation of the hybrid membranes encompassed an analysis of membrane structure, morphology, porosity, hydrophilicity, water flux, humic acid (HA) rejection, and the flux recovery ratio (FRR). The experimental outcomes unveiled notable changes in the morphology of the polymeric membrane when CNC and MWCNT were introduced into the PES membrane structure. All hybrid membranes displayed heightened hydrophilicity compared to the original pristine PES membrane. The PES/CNC0.3/CNT0.03 membrane demonstrated exceptional performance, with a remarkable HA rejection rate and FRR of 93.05% and 92.09%, respectively. This outstanding performance can be attributed to the synergistic combination of two separation mechanisms: electrostatic repulsion and size exclusion. The inclusion of MWCNTs into the hybrid membranes significantly reduced humic acid-induced membrane fouling due to improve surface hydrophilicity and decreased membrane roughness

Influence of dope composition of polyethersulfone membrane blend with cellulose nanocrystal and carboxylated multi-walled carbon nanotube on humic acid rejection

A full factorial experimental design was employed to investigate the dope composition of a membrane made of cellulose nanocrystal (CNC), multi-walled carbon nanotube (MWCNT), and polyethersulfone (PES) for its ability to reject humic acid (HA). Four factors were screened, including PES composition, polyvinylpyrrolidone content, CNC content, and carboxylated MWCNT content. The membranes were tested for HA rejection using a 10-ppm aqueous feed solution. The results indicated that the percentage of MWCNT had the most significant impact, contributing 72.31% to the overall contribution. The fabricated membranes exhibited high HA removal capacity of up to 90% for the membrane embedded with MWCNT. The model's predicted values agreed reasonably with the experimental data, indicating the model's validity. This study provides insights into the development of CNC/MWCNT/PES membranes for efficient HA rejection in water treatment applications

Microwave-assisted conversion of palm kernel shell biomass waste to photoluminescent carbon dots

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

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Eliminating food waste through technology- household

With the increase in household food wastes in Singapore, a mobile application FoodCord, was developed with the aim of reducing household food wastes. FoodCord has been successful in providing a convenient way to help users better plan and store their food products. The food products stored in a household highly reflects the nutritional intake of the household. Other than the increase in household food wastages, Singapore’s population has also faced an increase in health issues such as type 2 diabetes and high blood pressure in recent years. The cause of these issues is usually due to the overconsumption of certain nutritional factors such as calories, sugar, and cholesterol. Hence, the prime objective of this project is to extend on the existing features of FoodCord by introducing a way for users to manage their health based on the nutritional information of the food products stored in a user’s household. This report provides documentation on the new features implemented in FoodCord.Bachelor of Engineering (Computer Science

CAKE FILTRATION FOR SUSPENDED SOLIDS REMOVAL IN DIGESTATE FROM ANAEROBIC DIGESTED PALM OIL MILL EFFLUENT (POME)

Oil palm industry contributes significantly to the economic growth in Malaysia. At the same time, it generates a huge amount of palm oil mill effluent (POME) which contains valuable resources for energy, water and nutrients recovery. Currently, it has been used as feed for anaerobic biogas reactor to produce methane, a renewable energy source. The effluent discharged from the anaerobic digester, known as digestate, still contains abundant water and nutrients for recovery. However, the presence of suspended solids in digestate hinders the downstream water and nutrients recovery processes. Cake filtration process that has been successfully employed in water industry to remove suspended solids appears to be an attractive option for the removal of suspended solids in digestate. This paper investigates the performance of cake filtration process in removing suspended solids in digestate. Various types of filter aid such as perlite, diatomaceous earth (DE), bleaching earth (BE), powdered activated carbon (PAC), and boiler ash (BA) are used in this study. The amount of filter aid used as precoat and body feed was also varied (with ratio 1:1 from 1.0 g to 3.0 g) in the process. The effectiveness of cake filtration process was evaluated based on the quality of filtered digestate and the filtration flux. Overall, the particle size and size distribution of filter aids have huge influence on the cake filtration process. Turbidity removal above 90 % can be achieved regardless the type and amount of filter aids used. Due to the presence of plenty fine pores (as shown by FESEM image) on perlite particles and its narrow particle size distribution, the permeation of water was the highest flux (1 ml/cm2.min) and retention of suspended solids also was among the highest compared to other filter aids. This study shows that cake filtration process has the potential to be used to remove suspended solids in digestate so that the nutrient and water can be recovered in the following downstream process

Sonoelectrochemical processes for the degradation of persistent organic pollutants

The combination of electrochemistry and ultrasonic irradiation (sonoelectrochemistry) has gained increasing attention in recent years as a method for removing dissolved pollutants from water. This interest stems from the potential for sonoelectrochemical approaches to completely mineralise dissolved pollutants, converting them into harmless mineral species such as water and carbon dioxide. In many cases, the electrochemical and ultrasonic inputs into a sonoelectrochemical pollutant degradation process are found to be synergistic, producing a faster rate of degradation than that produced by the sum of the purely electrochemical or purely sonochemical inputs on their own. This synergism has several causes, with enhanced production of powerfully oxidising radicals and improved mass transport to and from the electrode surface being the two most often cited. In this review, we first give an overview of the various factors that impact on sonoelectrochemical pollutant degradation studies (including reactor design, sonochemical and electrochemical parameters and reaction conditions), before then discussing in detail examples of sonoelectrochemical processes for the degradation of persistent organic pollutants in water from 2015 onwards