The adequacy in uremic toxin removal upon hemodialysis treatment is essential in patients with kidney failure diseases as poor removal leads to heart failure, hypertension, and stroke. The combination of adsorption and diffusion processes has become very advantageous for hemodialysis membranes. By this mechanism, water-soluble uremic toxins (WSUTs) and protein-bounded uremic toxins (PBUTs) could be removed at one time. Therefore, this study aimed to develop a novel imprinted zeolite by p-cresol (IZC) and then incorporated it into polyethersulfone (PES) and poly(vinyl pyrrolidone) (PVP) to produce hollow fiber mixed matrix membrane (HF-MMM). The IZC proved to be sensitive in attracting the adsorbate, classifying it as having a strong adsorption behavior. Accordingly, IZC is very promising to be applied as an adsorbent in the hemodialysis treatment. In this study, IZC as p-cresol's adsorbent was incorporated into a PES-based polymeric membrane with a small addition of PVP to produce HF-MMM using a dry/wet spinning process. The effect of air gap distance between the spinneret and coagulant bath and percentage loading for PES, PVP, and IZC were studied and optimized to obtain the best performance of HF-MMM. The 40 cm of air gap distance, 16 wt% of PES, 2 wt% of PVP, and 1 wt% of IZC loading were able to produce a superior hemodialysis membrane. These optimized parameters showed sufficient uremic toxin removal, i.e., 60.74% of urea, 52.35% of p-cresol in the phosphate buffer saline solution, and 66.29% of p-cresol in bovine serum albumin solution for 4 h permeation using the dialysis system. These HF-MMMs also achieved pure water flux of 67.57 L m-2 h-1 bar-1 and bovine serum albumin rejection of 95.05%. Therefore, this membrane has proven to be able to clean up WSUT and PBUT through a one-step process. Moreover, as compared to the neat PES membrane, MMM was able to remove p-cresol at 186.22 times higher capability.
Humic acid removal requires ceramic membranes incorporated with metal organic framework (MOF) to display remarkable stability over water. Recent work has shown UiO-66, a Zr-based MOF, as an emerging material with the potential to fulfill this requirement. This work investigated the preparation, characterization and performance of UiO-66 particles deposited on alumina hollow fiber membranes. Concentrations of Zr precursors and synthesis period were varied in the preparation of UiO-66 using solvothermal synthesis. The presence of UiO-66 particles was characterized using the field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX) mapping, x-ray diffraction (XRD) and Brunauer–Emmett–Teller (BET) analysis. Pure water flux and humic acid rejection tests were carried out on both pristine alumina hollow fiber membranes and alumina hollow fiber membranes deposited with UiO-66 particles. In the former, a high pure water flux value of 231.24 L m−2 h−1 was recorded, while in the latter the recorded value dropped to 9.36 L m−2 h−1. Pristine ceramic hollow fiber membranes used to separate humic acid (1 g L−1) from an aqueous solution showed a rejection rate of 98%. When UiO-66 particles were deposited on the ceramic membranes, the solute flux of the membranes increased to 68.36 L m−2 h−1. Surprisingly, it was found that 99% humic acid was rejected from a feed solution using the membranes incorporated with UiO-66 particles. Findings showed that the weight loading of the UiO-66 particles on the alumina hollow fiber membranes was very low, showing a reading of only approximately ~ 0.01 g. Based on the adsorption-desorption analysis, at high pH values (≥ 9), UiO-66 particles and humic acid displayed a similar surface charge, creating a repulsion effect during the filtration process. UiO-66 particles on alumina hollow fiber membranes showed excellent stability, making it viable for water purification applications.
This paper reports the preparation of the dual layer ceramic hollow fiber membrane that made of alumina and a mixed ion electron conducting (MIEC) material for simultaneous reaction and separation applications. Alumina hollow fiber membrane was prepared using the phase inversion process followed by a sintering technique at elevated temperature. The alumina hollow fiber membrane was used as membrane support onto which a thin and dense layer of lanthanum strontium cobalt ferrite (LSCF) was deposited. The main objective of this study was to investigate the LSCF coating formulations used in the deposition of LSCF layer onto alumina substrate membrane. The sintering temperature of thin LSCF layer was varied to investigate gas-tightness properties of LSCF membrane. A series of characterizations were conducted for both the support and the LSCF membrane. The result showed that the thin layer membranes with thicknesses ranging from 3 to 20 μm were successfully deposited on the surface of alumina hollow fiber support. The sintering process improved the gas-tightness properties but the sintering temperature above 1150°C caused defects on the surface of LSCF membrane.
Recycling palm oil fuel ash (POFA) into lucrative holey graphene nanosheets will not only save resources but will also prove to be a great solution to avoid the hazards of environmental pollution. The present research aims on studying the effects of temperature and ratio of potassium hydroxide (KOH) during the chemical activation reaction of POFA, resulting in porous graphene sheets with great scope in a variety of industrial applications. These two parameters were studied because of their major influence on the yield, surface area, porosity, and quality of the produced graphene sheets. Porous graphene sheets were prepared by optimizing different activation temperatures (700 °C, 800 °C, and 900 °C) and POFA to KOH impregnation ratios (1:2, 1:3, 1:4, and 1:5). The optimal conditions for producing the best POFA-derived holey graphene in terms of the number of layers, surface area, and porosity were found with impregnation ratio of 1:3 and at temperature of 800 °C. From scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HR-TEM) analyses, it was found that the resulting few layer nanosheets have more uniform porosity at these optimized conditions. We found Brunauer-Emmett-Teller (BET) surface area, pore volume and carbon percentage of 1506.64 m2/g, 0.88 cm3/g and 99% respectively which are comparable to the previous findings using other biomass sources. It was also found that a higher temperature and higher KOH ratio resulted into pore widening and increasing the surface area, but at temperatures beyond the optimized conditions, the surface area and pore volume were reduced due to more vigorous reactions, and volatilization, which led to pore destruction. The present work emphasizes that these parameters have major impact on POFA activation, and their optimisation resulted into good quality graphene nanosheets in a greener and sustainable way, which can be used for many applications including inexpensive energy-storage and water purification applications.
The excessive presence of ammonia has led to serious potable water scarceness worldwide. This work aims to fabricate natural zeolite based hollow fibre ceramic membrane (HFCM) via phase inversion and sintering techniques for the ammonia removal in wastewater. The physical properties of the fabricated HFCM were investigated through morphologies, mechanical strength, dope suspension viscosity and pure water permeation also the performance test using synthetic wastewater. It was found that 5 cm, 15 mL/min and 1050 °C were the best fabrication conditions for the air – gap distance, bore fluid flow rate and sintering temperature, respectively. The membrane also revealed desired asymmetric structure, sufficient mechanical strength (50.92 MPa) and excellent pure water permeation flux (249.57 L/m2 h). Additionally, the ammonia removal gave an outstanding performance of 90% rejection. These findings show that natural zeolite based HFCM has a great potential to be developed as a single – step ammonia removal in wastewater.
A proper ventilation strategy in an isolation ward could promote better indoor air quality for the occupants. This could also reduce the risk of immunocompromised patients contracting healthcare-associated infections (HAI) or airborne diseases such as COVID-19, tuberculosis, and measles among others. This study aims to propose and examine appropriate ventilation strategies in a single-patient isolation ward that can reduce particle settlement in patients. A simplified CFD model of the isolation ward was developed and well-validated against established data. An RNG k-ε model and discrete phase model (DPM) were used to simulate airflow and particle transportation. The study examined the airflow and particle dispersion under a baseline case and four proposed ventilation strategies. Results showed that the baseline case study, which used the ceiling-mounted air curtain was insufficient to prevent the particles from dispersing into the vicinity of the patient. Likewise, the dilution effect under the baseline case and case 4 (wall-mounted air supply diffuser) were relatively weak due to the low air change rate (ACH) of 4/hr and 9/hr respectively. The ventilation strategy in case 4 has a negligible effect on reducing the particles (14%) settling on the patient although the ACH in case 4 was 2-times the baseline case. The present finding ascertains that utilising the combination of ceiling-mounted air diffuser and air curtain jet (case 3) results in zero particle settlement on both patient's and the patient's bed. It also reduced 57% of particles in the vicinity of the medical staff's breathing zone compared to the baseline case.
The fine-tuning of metal-organic frameworks (MOFs) can enable the development of effective adsorbents for the selective capture of less polarizable carbon dioxide (CO2) from flue gases. In this work, a series of bi-metallic MOFs with different doping concentrations (1-10 mol%) of magnesium (Mg) metal were synthesized by in situ metal substitution followed by post-synthetic functionalization with 10-50 wt.% polyethyleneimine (PEI). Detailed characterization confirmed the successful incorporation of the secondary metal and amine group into the MOF framework. Results showed that only up to 2 mol% of copper (Cu) can be substituted by Mg metal in the framework of MOF-199; further increase in Mg content disrupts the electrostatic equilibrium, leading to the formation of carbon matter-based copper nanoparticles instead. The sorption results showed that 1 and 2 mol% Mg-doped MOFs (MOF@Mg1 and MO@Mg2) demonstrated a CO2 uptake of 7.93 and 8.61 (mmol/g) respectively, at 1 bar and 273.15 K, showing 8.48 and 17.78% increase in adsorption capacity compared to the pristine MOF. Furthermore, 40 wt.% PEI-loaded MOF exhibited a 9.52% enhancement in CO2 adsorption selectivity. This work provides valuable insights into the synergistic effects of secondary metal doping and PEI impregnation on the morphology, structure, and CO2 adsorption performance of MOF-199.
Leptospirosis disease was caused by rat urine which contains the genus Leptospira bacteria. In this study, the fabrication of Pd-Fe-doped polyaniline nanocomposite thin films for the determination of the genus Leptospira bacteria thin films has been investigated. Pd-Fe-doped polyaniline nanocomposite thin films were fabricated by sol–gel spin coating method. The electrode sensors were immersed in the Leptospira solution. The resulting materials were investigated using field-emission scanning electron microscopy, atomic force microscopy, transmission electron microscopy, and current–voltage measurement. The atomic force microscopy images show the specific morphology films’ structure for Leptospira detection, whereas the field-emission scanning electron microscopy image shows the irregularity of clump nanoparticles in thin film surfaces. Transmission electron microscopy result shows that metal alloy (Fe-Pd) embedded in the polymer matrix. Current–voltage measurement with and without incubation of the thin film into Leptospira solution was done to show the relationship between concentration bacteria versus current. The result shows that polyaniline-Fe 0.4 -Pd 0.6 nanocomposite thin film has higher sensitivity in detecting Leptospira, where it has performed with the highest percentage of the sensitivity of 16.9%. Besides that, selectivity tests were conducted to distinguish the existence of Leptospira, Pseudomonas aeruginosa, and Staphylococcus aureus bacteria. These results confirm the potentials of polyaniline metal alloys’ nanocomposite thin films to be used for Leptospira bacteria detection in water.
The overgeneration of non-biodegradable waste in Indonesia requires empty lands for landfilling, which contravenes with the landscape of sustainable cities. As local landfills have become overburdened, the solid waste is disposed of in uncontrolled manners that seriously affect public health and the environment. To address this problem, Indonesian gradually moves towards digitalization for waste recycling. To reflect its novelty, this work investigates how to add economic value to recycled waste using digital technology and how economic incentives can be promoted to avoid generating waste. The roles and implications of digitalization on resource recovery are elaborated from Cleaner Production perspectives. As a driving force of social innovation, it was found that the digital transformation of waste industry encouraged community in Yogyakarta to sell waste online via Rapel app installed in their smartphones. On average, customers sell their waste nearly 15 kg per transaction and earn USD 0.1/kg as a point balance. When their waste ranges from 15 to 20 kg, the sellers get USD 1.4. Recovering polyethylene (PET) bottles via a mixed-recyclables could yield about USD 150–300/Mt, while a bottle-only collection ranges from USD 360 to 590/Mt. As the implications of this study, digitalization has created new jobs (780 waste collectors) in Yogyakarta (@20 persons/subdistrict). Digitalization in waste management also promotes waste avoidance up to 65%. Potential monthly turnover from the waste recycling's transaction through the app is about USD 2,000/waste bank. Overall, the findings imply that the digital transformation in the waste sector not only promotes the resource recovery of non-biodegradable waste for a circular economy, but also enables local community to do online transactions of recycled goods through mobile-based applications. By moving towards digitalization, it is projected that the country's waste recycling industry would create over 120,000 new jobs and absorb about 3.3 million informal workers such as waste collectors.
This work focused on the development of photocatalytic and antibacterial ZnO doped nanoparticles for wastewater treatment application. ZnO nanoparticle was successfully doped via a sol-gel method with different concentration of yttrium (Y), a rare-earth element. The improved properties of the structural, optical, photocatalytic and antibacterial after the nanoparticles doping modification were analyzed. XRD analysis confirmed the hexagonal (wurtzite) structure with average crystalline size between 10 to 22.7 nm. The exhibited XRD peaks that shifted towards lower angles after doping confirmed the Y3+ substitution in the ZnO structures. High-resolution transmission electron microscopy (HRTEM) showed an increase in grain size as the concentration of Y3+ ions inside the ZnO matrix increased. Ultraviolet-visible-near-infrared spectroscopic measurement revealed a red shift of the bandgap energy of 0.128 eV, which confirmed the substitution process. It was observed that the Y-dopant significantly improved the photocatalytic activity of the ZnO nanoparticles; 91.8%, 72.9%, 29.2% and 85.0% of 20ppm of HA, BPA, phenol and caffeine respectively under UVA light irradiation. In addition, Y-doped ZnO nanoparticle was found to be highly effective against S. aureus as compared to E. coli. The 9 wt.% Y-doped ZnO (9YZnO) nanoparticles have shown no bacterial growth at both minimum inhibitory concentration/minimum bacterial concentration MIC/MBC concentration which served as evidence of the improved antibacterial properties of the modified ZnO nanoparticles. Overall, in this study Y-doped ZnO nanoparticle had shown good performance as photocatalysis material in degrading organic compounds (natural, industrial and consumable organic compounds) and antibacterial material against germ positive microorganism.
