Chemical Cleaning Research Articles

High-efficiency cleaning technology and lifespan prediction for the ceramic membrane treating secondary treated effluent.

Chemical cleaning is one of the key technical means to control membrane fouling, restore membrane flux and ensure the stable operation of membrane systems. In the experiment, the six most representative chemical cleaning agents for ceramic membranes, such as sulfuric acid (H2SO4), sodium hydroxide (NaOH), sodium hypochlorite (NaClO), ethylenediaminetetraacetic acid disodium salt (EDTA-Na2), sodium dodecyl sulfate (SDS) and nonylphenol polyoxyethylene ether (OP-10), were used as research objects. The cleaning effect of the two-step combined cleaning of chemical cleaning agents on the fouled membrane was systematically investigated. Results showed that the order of the chemical cleaning agent had a significant effect on the cleaning effect. The best chemical cleaning program was determined to be NaClO first and then SDS: the fouled ceramic membrane was soaked in NaClO solution at 0.15% for 2.5 h and further soaked in SDS solution at five times its own critical micelle concentration for 2.5 h. The predicted long-term lifespan of the ceramic membranes was 4.91 years. Scanning electron microscopy-energy spectrum analysis showed that the surface roughness of the cleaned ceramic membrane was slightly higher than that of the new membrane. The contact angle was slightly lower than that of the new membrane.

Recovery of Membrane Permeability after Filtration of Sago Starch Suspension by Tangential Flow Filtration

Sago starch is extracted from the stems of the sago palm, Metroxylon sagu, in south-east Asia. Sago starch processing generates approximately 20 tons of starch containing effluents that can be recovered and marketed to sustain a small-scale industry. Tangential flow filtration (TFF) using microfiltration membranes (MFM) has been demonstrated as an effective method for separating suspended solids in biological effluents. When TFF was applied to concentrate sago starch suspensions (SSS), membrane permeability and lifecycle were impacted due to frequent fouling. This study evaluated cleaning methods to recover the permeability and extend the lifecycle of MFM following TFF application. Polysulfone membrane filter cassettes of pore size 0.45 µm and surface area 0.1 m2 were each used to separate starch in 100 L of SSS. Following separation, six chemical and physical cleaning methods were tested at laboratory-scale and the degree of cleaning was measured by normalized permeate flux (NPF) and normalized water permeability (NWP). The results showed that soaking the membranes in a 0.2 M NaOH solution (up to 91%, (p<0.05) within the shortest time of 72 h, (p<0.05) was the best cleaning method. The procedure has been utilized to maintain and extend the lifecycle of the MFM for streams containing starch suspensions.

Reverse osmosis pretreatment by a fluidized magnetic ion exchange resin for application in a power plant: Pilot-scale and high-rate operations and foulant characterization

Biofouling is one of the most serious problems in reverse osmosis (RO) operations. Here, we operated a pilot-scale MIEX® system with a high-rate configuration as a pretreatment for an RO system in a water purification plant. The goal was to investigate the RO foulants obtained with and without pretreatment by MIEX®. The MIEX® resin (10 to 300 mL/L) removed dissolved organic matter (DOM) within 5 min. A pilot-scale fluidized reactor with 100 mL/L of MIEX® removed 35.6%, 49.4%, and 56.2% of dissolved organic carbon (DOC) for effective resin doses of 0.03, 0.06, and 0.12 mL/L, respectively. Unknown screening analysis by Orbitrap mass spectrometry revealed that the MIEX® pretreatment decreased or removed 165–363 DOM features with carbon, hydrogen, and oxygen (CHO features) and 145–220 CHO features with N heteroatoms (CHON features) with effective resin doses of 0.03–0.12 mL/L. Moreover, fluorescence EEM revealed the preferential removal of terrestrial DOM, resulting in over half of the protein-like substances remaining in the RO feed. MIEX® selectively removed highly oxygenated DOM features within a short contact time, while condensed aromatic structures and lignin-like compounds were removed after 30 min. Increasing the MIEX® dose resulted in the additional removal of DOM features with less oxygenated characters and longer alkyl chains. The RO system with and without MIEX® pretreatment was similarly fouled by protein-like substances and CHON features; however, the MIEX® pretreatment decreased CHO features and terrestrial DOM foulants. The MIEX® pretreatment decreased organic and irreversible fouling and doubled the RO system lifetime, resulting in lower chemical cleaning and pressure requirements for an identical permeate volume.

Performance Evaluation of a Pilot-Scale Aerobic Granular Sludge Integrated with Gravity-Driven Membrane System Treating Domestic Wastewater

This study describes a novel integration of aerobic granular sludge (AGS) with a gravity-driven membrane (GDM) system at a pilot scale with a treatment capacity of approximately 150 L per day to treat raw domestic wastewater. The treatment performance and energy consumption of the AGS-GDM system were compared to the neighboring full-scale aerobic membrane bioreactor (AeMBR), treating the same wastewater at about 4000(±500) m3 per day. The AGS-GDM system demonstrated superior nutrient (nitrogen and phosphorus) removal as compared to the AeMBR. The GDM unit was continuously supplied with AGS-treated effluent. The GDM unit started with high [ >20 L per m2 per h (LMH) ] flux, which gradually declined. The flux remained quite stable after 15 days reaching 3 LMH after 35 days without any physical or chemical cleaning. Our results suggest that AGS-GDM is a viable technology for decentralized wastewater treatment and reuse in water-scarce regions. The AGS-GDM could easily replace conventional AeMBR technology in the wastewater treatment and reclamation market.

Testing of a new Yb:YAG fiber laser system for the removal of graphic vandalism from marble

Graphic vandalism causes detrimental effects on architectural stone surfaces. Among the cleaning methods developed in the last decades, laser cleaning showed considerable effectiveness but the available equipment still lacks full adaptability for the use on site, while the cleaning process is time-consuming for the site work requirements. In this paper, the feasibility of a fiber laser operating at 1064 nm (Yb:YAG) at high repetition rate (kHz) for the removal of vandal graffiti from marble is investigated, as it is potentially suitable for cleaning of large surfaces. Indeed, this device exploits a scan system covering a wider area than that of solid state lasers, while maintaining excellent portability. Evaluation of the cleaning procedure on a selection of spray paints and felt-tip permanent markers applied on marble mock-ups is carried out with a multimodal approach (optical microscopy combined with surface pattern reconstruction, colour monitoring, Fourier Transform Infrared spectroscopy in external reflection and ATR mode, Thin Layer Chromatography, Raman spectroscopy, thermal monitoring, scanning electron microscopy). Ablation and thermal effects are observed varying the laser setting and the type of paint layer, with repetition rate showing a strong impact on the type of interaction. Overall, best cleaning procedures are achieved for the thinning of the black marker and the removal of the black spray paint. Some residues on the best results were observed, suggesting that the laser needs to be integrated with a second step of chemical cleaning. This study, focused on graffiti removal, shows that fiber laser can be a useful tool for cleaning of large monumental surfaces.Graphical

Removal, Adsorption, and Cleaning of Pharmaceutical on Polyamide RO and NF Membranes.

Pharmaceuticals are present in various waters and can be almost completely rejected by membrane separation processes, i.e., nanofiltration (NF) and reverse osmosis (RO). Nevertheless, the adsorption of pharmaceuticals can decrease their rejection, so adsorption can be considered a very important removal mechanism. In order to increase the lifetime of the membranes, the adsorbed pharmaceuticals must be cleaned from the membrane. The used pharmaceutical (albendazole), the most common anthelmintic for threatening worms, has been shown to adsorb to the membrane (solute-membrane adsorption). In this paper, which is a novelty, commercially available cleaning reagents, NaOH/EDTA solution, and methanol (20%, 50%, and ≥99.6%) were used for pharmaceutical cleaning (desorption) of the NF/RO membranes used. The effectiveness of the cleaning was verified by Fourier-transform infrared spectra of the membranes. Of all the chemical cleaning reagents used, pure methanol was the only cleaning reagent that removed albendazole from the membranes.

A solar-driven degradation-evaporation strategy for membrane self-cleaning in the efficient separation of viscous crude oil/water emulsions

Membrane separation techniques are promising methods for effectively treating hazardous emulsified oily wastewater, but membrane fouling remains a serious challenge because the high viscosity and complex composition of crude oil make it easy to adhere to membranes and difficult to be removed by conventional physical or chemical cleaning means. Herein, a two-stage solar-driven (photo-Fenton degradation/evaporation) strategy was proposed to realize the self-cleaning of membranes fouled by viscous crude oil (>60,000 mPa s), wherein the photo-Fenton process helped to degrade the heavy components into light components, and all light components removed during the solar-driven evaporation process. A 1D/2D heterostructure membrane with photo-Fenton activity and anti-crude-oil-fouling performance was prepared via a facile self-assembly vacuum-assist method. The addition of rod-like g-C3N4 (RCN) increased the interlayer distance of α-FeOOH/porous g-C3N4 (FPCN) nanosheets, resulting in a high permeation flux. The FPCN–RCN membrane exhibited both high permeation flux of 779 ± 19 L m–2h–1bar–1 and a separation efficiency of 99.4% for highly viscous crude oil-in-water emulsion. Importantly, the viscous crude oil fouled on the membrane was completely removed by the photo-Fenton degradation/solar-driven evaporation strategy, and the flux recovery rate of the membrane was ∼100%. Therefore, the FPCN–RCN membrane combined with the novel self-cleaning strategy exhibits great potential for practical emulsified oily wastewater treatment.

Microbiological evaluation in invisible aligner chemical cleaning methods against Candida albicans and Streptococcus mutans

This study aimed to assess the efficacy of chemical agents in removing Candida albicans and Streptococcus mutans biofilm from invisible aligners. The samples were made of EX30 Invisalign trays, biofilm was cultured by standardized suspensions of C. albicans ATCC strain and S. mutans clinical strain on the sample. The treatments used were 0.5% sodium hypochlorite (NaClO) (20 minutes), 1% NaClO (10 minutes), chlorhexidine (5 minutes), peroxide (15 minutes), and orthophosphoric acid (15 seconds). The control group received phosphate-buffered saline for 10 minutes. The colony-forming units per milliliter of each microorganism were determined by serial dilutions seeded in plates with selective culture mediums for each one. Data were analyzed by the Kruskal-Wallis and Conover-Iman tests at an α of 0.05. For the C. albicans biofilm group, the control group had 9.7 Log10 of microorganism growth, and all treatment groups had statistically significant biofilm reduction, in which chlorhexidine presented the highest inhibition of 3 Log10, followed by alkaline peroxide and orthophosphoric acid both with 2.6 Log10, 1% NaClO (2.5 Log10), and 0.5% NaClO (2 Log10). As for S. mutans, the control group had 8.9 Log10 of growth, and a total microorganism inhibition was reached by chlorhexidine, 1% NaClO, and orthophosphoric acid, whereas alkaline peroxide inhibited growth to 7.9 Log10 and 0.5% NaClO 5.1 Log10. Within the limitations, chlorhexidine and orthophosphoric acid had greater efficacy in both biofilms. In addition, 1% NaClO and alkaline peroxide also had significant effects; therefore, their incorporation aligners disinfection protocols are valid.

Structural and performance variation of PES/PVDF membranes after exposure to the pretreated feed water of CECs

In this study, the removal efficiency of chemicals of emerging concerns (CECs) was evaluated under exposure to various doses of UV/H2O2-based oxidation processes in combination with membrane filtration for three cleaning cycles. Polyethersulphone (PES) and polyvinylidene fluoride (PVDF) materials based membranes were used for this study. The chemical cleaning of the membranes was performed by immersion of the membranes into 1 N HCl followed by adding 3000 mg.L−1 NaOCl for 1hr. Degradation and filtration performance was evaluated using Liquid Chromatography with tandem mass spectrometry (LC-MS/MS) and total organic carbon (TOC) analysis. Membrane fouling analysis for assessing the comparative performance of PES and PVDF membranes was determined by specific fouling and fouling indices evaluation. Membrane characterization results show that the alkynes and carbonyl group formation are due to dehydrofluorination and oxidation of PVDF and PES membranes under the attack of foulants and cleaning chemicals, which resulted in a reduction of fluoride percentage and an increase in sulfur percentage in the PVDF and PES membranes. A decrease in the hydrophilicity of the membranes in underexposed conditions was observed and is consistent with an increase in dose. Degradation results of CECs follow with the highest removal efficiency of chlortetracycline (CTC) followed by atenolol (ATL), acetaminophen (ACT), and caffeine (CAF) degradation due to attack on the aromatic ring and the carbonyl group of CECs by OH exposure. Membrane exposed at 3 mg.L-1 dose of UV/H2O2-based CECs shows minimum alteration with higher filtration efficiency and lower fouling, particularly in PES membranes.

Osmotic cleaning of typical inorganic and organic foulants on reverse osmosis membrane for textile printing and dyeing wastewater treatment

Reverse osmosis (RO) is one of the most fundamental membrane technology because it has higher salt rejections, which suffers from the issue of membrane fouling, as the membrane is inevitably exposed to foulants during the filtration process. For different fouling mechanisms of RO membrane, physical and chemical cleaning are widely used in the control of RO membrane fouling. The present study investigated the performance and water flux recovery using osmotic cleaning to clean the typical inorganic and organic foulants on RO membrane for textile printing and dyeing wastewater treatment. The effects of operation conditions (i.e., the concentration of cleaning solution, the filtrating time and cleaning time, and the flow rate of cleaning solution) on relative water flux recovery were examined. The results show that a highly water flux recovery (98.3% for cleaning of inorganic fouling and 99.6% for cleaning of organic fouling) was achieved under optimal operation of the concentration and flow rate of cleaning solution and the filtrating and cleaning time. Moreover, the experiment of repeated “filtrating-cleaning” cycles indicated that the osmotic cleaning has highly performance of recoverability of water flux (over 95.0%) can be extended in a relatively long time. The experimental results and changes on SEM and AFM images of RO membrane confirmed the successful development and application of osmotic cleaning for inorganic and organic fouling of RO membrane.

Improvement in extraction and sensory properties of soapnut extract by fermentation

Abstract Sapindus saponins are potential biosurfactants that can widely be used to replace many chemical cleaning products. This study aimed to investigate the water extraction of saponins from the pericarps of Sapindus mukorossi and enhance the sensory properties of the extract by yeast fermentation. Extraction conditions including temperature, solid-to-liquid ratio, extraction time, and number of extraction times were studied. A yield of 21.4% was obtained by 2 h of extraction at 80 °C with a solid-to-liquid of 1/6 (w/v) and two times. Fermentation was used to purify the Sapindus extract, inoculum amount and fermentation time were optimized. The fermentation by S. cerevisiae (2%) within 4 days significantly improved the color and smell of aqueous extract, turbidity decreased by 75.6%, total sugar content decreased by nearly 50% and saponins content slightly decreased. These results could contribute to the development of industrial–scale production of Sapindus saponins.

A gravity-driven membrane bioreactor in treating the real decentralized domestic wastewater: Flux stability and membrane fouling

Domestic wastewater in decentralized sites is capturing increasing attention. However, conventional treatment technology is not sufficiently cost-effective. In this study, real domestic wastewater was treated directly using a gravity-driven membrane bioreactor (GDMBR) at 45 mbar without backwashing or chemical cleaning, and the effects of different membrane pore sizes (0.22 μm, 0.45 μm, and 150 kDa) on flux development and contaminants removal were examined. The results showed that the flux initially decreased and then stabilized throughout long-term filtration and that the stabilized flux level of the GDMBR equipped the membranes with the pore size of 150 kDa and 0.22 μm was higher than that of 0.45 μm membrane and was in the range of 3–4 L m−2h−1. The flux stability was related to spongelike and permeable biofilm generation on the membrane surface in the GDMBR system. The presence of aeration shear on the membrane surface would cause the slough off of biofilm from the membrane surface, especially in the scenarios of GDMBR with the membrane pore size of 150 kDa and 0.22 μm, contributing to lower accumulation of extracellular polymeric substance (EPS) and smaller biofilm thickness compared to that of 0.45 μm membrane. Furthermore, the GDMBR system achieved efficient removals of chemical oxygen demand (COD), and ammonia, with average removal efficiencies of 60–80% and 70%. The high biological activity and microbial community diversity within the biofilm would improve its biodegradation and should be responsible for the efficient removal performance of contaminants. Interestingly, the membrane effluent could effectively retain total nitrogen (TN) and total phosphorus (TP). Therefore, it's feasible to adopt the GDMBR process to treat the actual domestic wastewater in the decentralized locations, and these findings could be expected to develop some simple and environmentally friendly strategies for decentralized wastewater treatment with fewer inputs.

Impact of microplastics on organic fouling of hollow fiber membranes

Given the potential hazards of microplastics (MPs), it is desirable to efficiently remove them during wastewater treatment processes. To this end, ultrafiltration (UF) membranes can significantly increase the removal of MPs, however the fouling of such membrane modules can also be impacted by the presence of MPs. Magnetic Resonance Imaging (MRI) was used here to non-invasively quantify the effect of polyethylene (PE) MPs accumulation in a 3D UF hollow fiber (HF) membrane module containing 400 fibers, via direct non-invasive velocity imaging of the flow distribution between individual fibers during module operation. The co-effect of MPs and alginate (a common organic model foulant mimicking extracellular polymeric substances (EPS)) on fouling of the HF module was then explored. Flow was initially equally distributed with fouling causing flow in particular fibers to be significantly reduced. Fouling with MPs resulted in minimal flow distribution disruption and was easily remediated hydraulically, in contrast alginate fouling required chemical cleaning in order to fully restore homogeneous flow distribution between the fibers. The presence of both MPs and alginate resulted in a more heterogeneous disruption of the fibre flow distribution due to fouling and resulted in much more effective hydraulic cleaning of the module.

Three-Dimensional Printed Resin: Impact of Different Cleaning Protocols on Degree of Conversion and Tensile Bond Strength to a Composite Resin Using Various Adhesive Systems.

The present investigation tested the effect of cleaning methods and adhesives on the tensile bond strength (TBS) of a resin-based composite luted to a temporary 3D printed resin. Substrates (n= 360) were printed using a Rapidshape D20II and cleaned with a butyldiglycol-based solution, isopropanol, or by centrifugation. Specimens were air-abraded with Al2O3 (mean particle size 50 µm) at 0.1 MPa followed by pretreatment (n = 30/subgroup) with: (1) Clearfil Ceramic Primer (CCP); (2) Clearfil Universal Bond (CUB); (3) Scotchbond Universal Plus (SUP) or 4. Visio.link (VL) and luted to PanaviaV5. TBS (n = 15/subgroup) was measured initially (24 h at 37 °C water) or after thermal cycling (10,000×, 5/55 °C). The degree of conversion (DC) for each cleaning method was determined prior and after air-abrasion. Univariate ANOVA followed by post-hoc Scheffé test was computed (p < 0.05). Using Ciba-Geigy tables and chi-square, failure types were analyzed. The DC values were >85% after all cleaning methods, with centrifugation showing the lowest. CCP pretreatment exhibited the lowest TBS values, with predominantly adhesive failures. The combination of CCP and centrifugation increased the TBS values (p < 0.001) compared to the chemical cleaning. CUB, SUP, and VL, regardless of cleaning, can increase the bond strength between the 3D printed resin and the conventional luting resin.

Improving kinship probability in analysis of ancient skeletons using identity SNPs and MPS technology.

In forensic kinship analysis and human identification cases, analysis of STRs is the gold standard. When badly preserved ancient DNA is used for kinship analysis, short identity SNPs are more promising for successful amplification. In this work, kinship analysis was performed on two skeletons from the Early Middle Ages. The surface contaminants of petrous bones were removed by chemical cleaning and UV irradiation; DNA was isolated through full demineralization and purified in an EZ1 Advanced XL machine. The PowerQuant kit was used to analyze DNA yield and degradation, and on average, 17 ng DNA/g of petrous bone was obtained. Both skeletons were typed in duplicate for STR markers using the Investigator EssplexPlus SE QS kit, and comparison of partial consensus genotypes showed shared allelic variants at most loci amplified, indicating close kinship. After statistical calculation, the full-sibling kinship probability was too low for kinship confirmation, and additional analyses were performed with PCR-MPS using the Precision ID Identity Panel. The HID Ion Chef Instrument was used to prepare the libraries and for templating and the Ion GeneStudio S5 System for sequencing. Analysis of identity SNPs produced full genetic profiles from both skeletons. For combined likelihood ratio (LR) calculation, the product rule was used, combining LR for STRs and LR for SNPs, and a combined LR of 3.3 × 107 (corresponding to a full-sibling probability of 99.999997%) was calculated. Through the SNP PCR-MPS that followed the STR analysis, full-sibling kinship between the ancient skeletons excavated from an early medieval grave was confirmed.

Identification of an unusual pale green material on the surface of an ancient Chinese bronze vessel and application of laser cleaning to its removal

An ancient Chinese bronze vessel represented a typical difficult situation for conservation: a large quantity of an unwanted pale green material of unknown nature adhered to a surface fully decorated with delicate relief. The diagnostic itinerary, beginning with in-situ Raman spectroscopy analysis and followed by scanning electron microscopy-energy dispersive spectroscopy and X-ray diffraction, was found to be advantageous in revealing the presence of both inorganic and organic compounds in the pale green material. Irradiation with pulsed Nd:YAG 1064 nm laser in LQS regime (100 ns) followed by chemical cleaning using a low-toxicity solvent mixture proved to be respectful towards the original patina of the bronze as well as of high efficiency. Tentative analyses with the Raman spectroscopy and hyperspectral imaging were conducted to provide further indications on quality and visual effect during the cleaning result assessment. In parallel with the analyses and interventions on the bronze vessel, experiments were also carried out on mock-up samples in order to further explore the Raman scatter property and reactivity with laser ablation of mixed materials. The study provided reference for the optimization of diagnostic and conservation for the bronze artwork with similar situation.

Base-activated persulfate strategy for ceramic membrane cleaning after treatment of natural surface water

The natural organic matters (NOM) have been proved to form the hydraulically irreversible membrane fouling, which limit the application of the membrane in water treatment processes. To solve the membrane fouling caused by NOM, a novel one-step chemical cleaning method for the ceramic membrane derived from the base-activated persulfate oxidation process was developed in this study. When the SiC ceramic membranes was used to filtrate practical river water, the permeate flux dropped 65% as ΔTMP reached 30 kPa. After 2 h immersion of the fouled membrane in the cleaning solution (2 mM PMS and 8 mM NaOH), the flux recovery rate nearly reached 100%. Direct backwash of the membrane by the above cleaning solution further reduced the cleaning time to 25 mins, while achieving similar cleaning effect. Then the cleaned membranes were immersed in NaClO solution to release all the residual foulants, but the fluorescence excitation-emission matrix spectra (EEM) and total organic carbon (TOC) of the solution were found insignificant, which demonstrated the base-activated persulfate strategy had effectively removed the irreversible membrane fouling. Free radical quenching experiments were carried out and·O2- was identified as the dominant ROS responsible for the removal of the membrane foulants. The permeate flux and filtration efficiency of the SiC membrane were stable after 5 consecutive fouling-cleaning cycles, and the membrane structure was not damaged. In summary, the base-activated persulfate strategy is an efficient and cleaner method for SiC membrane cleaning, which is potential to be applied in practical membrane water treatment process.

Use of Alteromonas sp. Ni1-LEM Supernatant as a Cleaning Agent for Reverse-Osmosis Membranes (ROMs) from a Desalination Plant in Northern Chile Affected by Biofouling.

Biofouling refers to the undesirable growth of microorganisms on water-submerged surfaces. Microfouling, the initial state of biofouling, is characterized by aggregates of microbial cells enclosed in a matrix of extracellular polymeric substances (EPSs). In seawater desalination plants, filtration systems, such as reverse-osmosis membranes (ROMs), are affected by microfouling, which decreases their efficiency in obtaining permeate water. The existing chemical and physical treatments are expensive and ineffective; therefore, controlling microfouling on ROMs is a considerable challenge. Thus, new approaches are necessary to improve the current ROM cleaning treatments. This study demonstrates the application of Alteromonas sp. Ni1-LEM supernatant as a cleaning agent for ROMs in a desalination seawater plant in northern Chile (Aguas Antofagasta S.A.), which is responsible for supplying drinking water to the city of Antofagasta. ROMs treated with Altermonas sp. Ni1-LEM supernatant exhibited statistically significant results (p < 0.05) in terms of seawater permeability (Pi), permeability recovery (PR), and the conductivity of permeated water compared with control biofouling ROMs and those treated with the chemical cleaning protocol applied by the Aguas Antofagasta S.A. desalination plant.

Telaah Pustaka: Berbagai Metode dan Bahan Pembersihan Gigi Tiruan Lepas

Cleaning of removable dentures is an important step to prevent cross-contamination and contribute to the health of the patient, the lifespan of the dentures, and the patient's overall quality of life. Bad dentures have undesirable effects such as bad breath, stains and biofilms, and calculus accumulation in the dentures which can lead to denture stomatitis, angular cheilitis, and poor oral health. A dentist is responsible for educating the patient after denture insertion so it will increase the knowledge of the denture wearer how to maintain the cleanliness of the denture properly. There are two methods for cleaning removable dentures, mechanically and chemically. Mechanical cleaning is done by removing plaque using a brush or ultrasonic cleaning. Meanwhile, chemically using chemical cleaning products such as hypochlrorite, peroxide, neutral peroxide dengan enzyme, enzyme, or acids. Recommended method for cleaning dentures is a combination method combining mechanical and chemical method.

Inhibition caused by adsorption of organic micropollutants (MPs) on PES@CoFe2O4 polymeric ultrafiltration membranes and the enhanced MPs degradation by a continuous pH regulation

In this work, catalytic membranes were fabricated by blending CoFe2O4 catalysts into polyethersulfone (PES) and then used to treat naproxen with the addition of peroxymonosulfate (PMS). It was found that the addition of PMS results in a decrease in pH, which increases the adsorption of naproxen. This often overlooked phenomenon is demonstrated here to have an important role since the adsorption of naproxen on the polymeric matrix and catalytic particles decreases the degradation efficiency of naproxen. To verify this hypothesis and rule out the decrease in pH after the addition of pH, two ways of controlling the pH of the naproxen solution were compared: adjusting pH before and after the addition of PMS, respectively. Our results indicate that in the batch experiment, adjusting the pH of naproxen solution after adding PMS led to a dramatic 23-fold increase in the kinetic constant of the naproxen oxidation (0.42/min, pH6) compared to when pH was adjusted before adding PMS (0.018/min, pH 6). This enhancement in the overall kinetics was attributed to the elimination of the inhibition caused by MPs adsorption at low pH. In a dead-end cell, the catalytic membranes with 2.0 % of CoFe2O4 achieved quantitative conversion of naproxen, bisphenol A, and atrazine, with values of 98 %, 97 %, and 74 %, respectively, demonstrating the efficacy of this approach to convert multitype of MPs in wastewater streams. In a reusability study, the naproxen removal of the catalytic membranes with 2.0 % of CoFe2O4 decreased by 81 % and 45 % after 5 rounds in the batch experiment and dead-end cell, respectively. However, with a chemical cleaning process between each round, the degradation efficiency can be effectively recovered, proving the negative effects of the adsorption of MPs or their intermediates during the SR-AOPs. Our work demonstrates that pH in SR-AOP-based catalytic membrane processes determined both the reaction rate and the adsorption of MPs or their intermediates on the membrane and its reactive sites. We envision that these results will be valuable in developing efficient catalytic membranes for the treatment of MPs in wastewater streams.