Ultrapure Water Production Research Articles

Biostability assessment of ultrapure water piping materials in the semiconductor industry and their susceptibility to Ralstonia growth

The pipes used for ultrapure water (UPW) distribution are constructed using high-quality materials to ensure purity. However, there remains a risk of contamination based on the pipe type. This study is the first to comprehensively evaluate the biological implications of various UPW pipe materials used in the semiconductor industry. The results showed that Polyvinylidene fluoride (PVDF) exhibited lower organic carbon leaching (0.08 mg/L) and a reduced biomass formation potential (BFP) (approximately 5 × 105 cells/cm2) compared to chlorinated polyvinyl chloride (CPVC) pipes. In particular, Ralstonia, an oligotrophic bacterium commonly found in UPW systems, formed a significant biofilm on pipe surfaces, notably in stainless steel (SUS) and CPVC pipes. Furthermore, particle contamination, a critical concern in semiconductor manufacturing, was investigated, focusing on potential contamination sources generated by pipe leaching and the presence of bacteria. The bacterial composition of the selected UPW was investigated, revealing Herbaspirillum, a nitrogen-fixing bacterium, as the dominant species, account for 66.15 %. Notably, the composition of the feedwater was different from that of the UPW. This study also highlights the limitations of culture-based methods, particularly in detecting bacteria under oligotrophic conditions, which are often unculturable. Flow cytometry (FCM) shows promise for the quick detection of bacterial contamination by providing total cell counts. Moreover, cytometric fingerprinting analysis revealed phenotypic differences between the communities. Nevertheless, further development of a simplified and widely applicable cell counting protocol is required for its effective integration into UPW production.

High recovery design of reverse osmosis process with high permeate water quality and low wastewater discharge for ultra-pure water production

Ultra-pure water (UPW) for electronic industry is produced via many unit processes including reverse osmosis (RO), pretreatments, membrane degasifier, and ion exchange processes. Generally, 2-pass RO system is adopted in UPW production process to remove ionic and organic matters to meet water quality requirements of post-treatments. Since RO concentrate occupies most of wastewater discharged from UPW production process, high recovery design is beneficial to reduce wastewater discharge. According to the solution-diffusion model, permeate concentrations increase at higher feed concentrations, which may limit to increase RO recovery. Interestingly, the bench-scale 2-pass RO test using five commercial membrane modules revealed permeate concentrations were not affected by feed concentrations below a critical value (35 mg/L as NaCl in this work). This means the first-pass RO recovery can be increased without decreasing permeate water quality as far as second-pass RO feed concentrations are below the critical values. Various 2-pass UPW-RO system designs (250 mg/L as NaCl of feed concentration) were analyzed using an industrial RO system simulator to investigate the effect of the first- and second-pass recovery. The simulation works found that increasing the first- and second-pass recovery decreased wastewater discharge, energy consumption, and the number of membrane modules without degrading permeate water quality.

Multiple Roles of Anions on the Degradation Efficiency and Mineralization Pathway of Recalcitrant Acetaldehyde by Vacuum Ultraviolet (185 nm) Oxidation.

Vacuum-UV (185 nm, VUV) is widely applied to polish reverse osmosis permeate (ROP), such as the production of electronics-grade ultrapure water. In this study, the VUV oxidation of acetaldehyde, a common carbonyl in ROP, was found to be influenced by anions even at low concentrations. Interestingly, the influencing extent and mechanism varied depending on the anions. Bicarbonate minimally affected the VUV-photon absorption and •OH consumption, but at 5000 μg-C·L-1, it decreased the degradation of acetaldehyde by 58.7% possibly by scavenging organic radicals or other radical chain reactions. Nitrate strongly competed for VUV-photon absorption and •OH scavenging through the formation of nitrite, and at 500 μg-N·L-1, it decreased the removal rate of acetaldehyde degradation by 71.2% and the mineralization rate of dissolved organic carbon by 53.4%. Chloride competed for VUV-photon absorption and also generated reactive chlorine species, which did not affect acetaldehyde degradation but influenced the formation of organic byproducts. The radical chain reactions or activation of anions under VUV irradiation could compensate for the decrease in oxidation performance and need further investigation. In real ROPs, the VUV oxidation of acetaldehyde remained efficient, but mineralization was hindered due to nitrate and chloride anions. This study deepens the understanding of the photochemistry and feasibility of VUV in water with low concentrations of anions.

(Invited) Trials and Tribulations on Scaling Metal Recovery Technology from Lab to Market

PowerTech Water, Inc. d/b/a ElectraMet (ElectraMet) is a cleantech company founded in 2014 in Lexington, KY with the goal of applying carbon and electrochemistry to solve fundamental challenges in wastewater and process water applications. There exists a broad array of separation applications that could be tackled through electrochemical routes, and ElectraMet has worked on many of them.Early in ElectraMet’s history, focus was directed towards salt removal applications such as salt-free water softening, brackish water desalination, and ultra-pure water production. While some traction was found in these spaces, penetration of a new technology versus entrenched incumbents such as reverse osmosis and distillation made the sales process difficult. Limitations in what the technology could and could not do were also determined. Therefore, within the first few years of operation, focus shifted towards particular customer pain points, specifically metals separation applications. Problematic metals concentrations are present in drinking water, industrial effluents, and storm runoff, just to name a few. As a growing but still small business, it is important to choose a beachhead market where you can have the strongest value proposition, and electrochemical separations of metals offered a unique opportunity to solve challenges in the metals separation space. Therefore, considerable work has gone into developing these separation processes for specific metals and specific markets.In this talk, the early history of the company will be reviewed, including technology, funding, and market applications. The impact of strategic advisors and early successes will be discussed with regards to the direction of the company. Ultimately, product-market-fit and the strategies and struggles in building a small business will be presented. Efforts will be made to highlight possible pitfalls, roadblocks, and opportunities as seen through this particular journey.

Effect of Ion-Exchanger Monoporosity in the Kinetics of Oxygen Sorption by Silver-Containing Nanocomposites

The results of a study of the kinetics of oxygen sorption from water by silver-containing nanocomposites synthesized on the base of macroporous ion exchangers with different pore sizes are presented. In the case of the Lewatit K 2620 ion exchanger, the pore size was fixed (41 nm), and for KU-23, it varied in the range from 10 to 100 nm. The nanocomposite materials Ag0⸱KU-23 and Ag0⸱Lewatit K 2620 were prepared by chemical precipitation. Using the different physicochemical methods, it was found that due to the monoporosity of the ion exchanger, the average size of the silver particles in the Ag0⸱Lewatit K 2620 nanocomposite is smaller than for KU-23. This effect contributes to the intensification of oxygen absorption and is proved by the results of studying the rate and degree of oxygen sorption by nanocomposites in the entire studied range of their capacity on metal. On the other hand, the polyporosity of the KU-23 ion exchanger, due to its better diffusion permeability, contributes to the more uniform distribution of silver over the volume of nanocomposite grains and ensures the steady state of the sorption process. Based on the presented experimental results, the synthesized silver-containing nanocomposites can be recommended as multifunctional materials with bactericidal action and catalytic effect for different industrial applications, including the deep removal of dissolved oxygen in the production of ultrapure water for energetics and microelectronics.

Phase behavior of sodium and potassium salts in their aqueous solutions: Experiment and computational thermodynamics

AbstractWith the rapid development of the semiconductor industry, the demand for ultraclean and high‐purity electronic chemicals, especially ultrapure water as a general solvent for cleaning semiconductor chips, has increased dramatically. The distillation process is a good choice for large‐scale production of ultrapure water that can be used to clean semiconductor chips, but there is a lack of basic thermodynamic theory for removing ionic impurities. In this work, the temperature and vapor–liquid phase composition of sodium and potassium salts aqueous solutions at vapor–liquid equilibrium (VLE) were investigated by experiments. The microstructure of each inorganic salt aqueous solution was explored by molecular dynamics simulation and quantum chemical calculation, and the interaction between each ion and water molecule was analyzed. A volatilization mechanism of inorganic salts was proposed, and it was found that the volatilization of inorganic salts in an aqueous solution was affected by the strength of interaction between the dissociated anions and cations and water molecules. Finally, the conductor‐like screening model segment activity coefficient (COSMO‐SAC) model predicted the VLE values of inorganic salt aqueous solutions. The prediction at low concentrations (xs < 0.06) was in good agreement with the experimental data.

Integration of capacitive deionization and forward osmosis for high water recovery and ultrapure water production: concept, modelling and performance analysis

ABSTRACT Forward Osmosis (FO), a membrane desalination technology and Capacitive Deionization (CDI), an electrically operated desalination technology, are numerically integrated utilizing four different configurations for the high-water recovery rate and ultrapure water production from brackish water resource. To minimize the wastewater rejection, the CDI desorption stream is continuously fed to the FO unit, efficiently recovering the remaining freshwater. To produce ultrapure water, freshwater stream obtained from FO is provided to the CDI cell, which adsorbs the remaining dissolved solute particles. These two configurations serve the purpose of both industrial as well as domestic water supply requirements. Continuing this concept, the formation of the other two configurations allows us to obtain fresh water and ultrapure water simultaneously and up to a 90% freshwater recovery rate for the areas with inadequate supply. The performance parameters to assess the integration are the Water Recovery Rate (WRR) and Specific Energy Consumption (SEC). The first configuration (CDI-FO), proposed for a high freshwater recovery rate, resulted in 79.33% WRR with an SEC of 0.689 kWh / m 3 . While, for the second configuration (FO-CDI), 34.25% water was recovered as 2.87 ppm ultrapure water along with 34.25% freshwater. The third proposed configuration (CDI-FO-CDI) had a WRR of 79.33%, 14.67% of which was recovered as ultrapure water of concentration 2.86 ppm. The fourth configuration (CDI-FO-FO) developed for high water recovery, removed the maximum of water from the feed stream with a WRR of 91.33% and remained energy-efficient, consuming an SEC of 0.908 kWh / m 3 .

Powdered activated carbon (PAC)-assisted peroxymonosulfate activation for efficient urea elimination in ultrapure water production from reclaimed water

Urea is a problematic pollutant in reclaimed water for ultrapure water (UPW) production. The sulfate radical-based advanced oxidation process (SR-AOP) has been recognized as an effective method for urea degradation. However, conventional metal-based catalysts for peroxymonosulfate (PMS) activation are unsuitable for UPW production due to issues related to metal ion leaching. In this study, the use of powdered activated carbon (PAC) was investigated for the removal of urea from reclaimed water. The PAC exhibited a high degree of defects (ID/IG = 1.709) and various surface oxygen functional groups (C–OH, C=O, and C–O), which greatly enhanced its catalytic capability. The PAC significantly facilitated PMS activation in the PMS + PAC system, leading to the complete urea decomposition. The PMS + PAC system demonstrated excellent urea removal efficiency within a wide pH range, except for pH < 3. Among the various anions present, the CO32− and PO43− inhibited urea degradation, while the coexistence of Cl− promoted urea removal. Furthermore, the feasibility test was evaluated using actual reclaimed water. The quenching test revealed that SO4−·, ·OH, and O2−· played crucial roles in the degradation of urea in the PAC-assisted SR-AOP. The oxygen functional groups (C–OH and O–C=O) and defect sites of PAC clearly contributed to PMS activation.

Enhanced Salt Removal of Fresh Water by Recovery-Reduced Ion Concentration Polarization Desalination.

Here, we examine electromembrane systems for low-concentration desalination applicable to ultrapure water production. In addition to electrodialysis and ion concentration polarization (ICP) desalination, we propose a recovery-reduced ICP strategy for reducing the width of the desalted outlet for a higher salt removal ratio (SRR). The correlation between conductivity changes and thickness of the ion depletion zone is identified for electrodialysis, ICPH (1:1), and ICPQ (3:1) with a low-concentration feed solution (10 mM, 1 mM, 0.1 mM NaCl). Based on the experimental results, the scaling law and SRR for the electroconvection zone are summarized, and current efficiency (CE) and energy per ion removal (EPIR) depending on SRR are also discussed. As a result, the SRR of electrodialysis is mostly around 50%, but that of recovery-reduced ICP desalination is observed up to 99% under similar operating conditions. Moreover, at the same SRR, the CE of recovery-reduced ICP is similar to that of electrodialysis, but the EPIR is calculated to be lower than that of electrodialysis. Considering that forming an ion depletion zone up to half the channel width in the electromembrane system typically requires much power consumption, an ICP strategy that can adjust the width of the desalted outlet for high SRR can be preferable.

Combined impacts of aluminum and silica ions on RO membrane fouling in full-scale ultrapure water production facilities

In this study, a fouled reverse osmosis (RO) membrane from a full-scale ultrapure water (UPW) facility was autopsied and investigated to propose the fouling mechanism and mitigation strategies. Although the influent was introduced to the coagulation and ultrafiltration as the pre-treatment processes, thick fouling layers were found over the entire RO surface. The foulant was mainly composed of aluminum silicates due to the elevated Al concentration (up to 100 μg/L) originated from the coagulation process utilizing polyaluminum chloride, and high recovery (up to than 90%) of RO process. Lab-scale fouling tests also confirmed that the elevated Al concentration in the RO influent contributed to significant flux decline due to a bridging effect with negatively charged organic matter and the formation of aluminum silicates. The application of polydiallyldimethylammonium chloride as an alternative coagulant successfully mitigated the organic and silicate fouling. Therefore, control of the residual aluminum ions originated from the coagulation process is critical to mitigate both organic and inorganic fouling on RO membrane surfaces during the production of UPW.

Removal of urea in ultrapure water system by urease-coated reverse osmosis membrane

Among the various substances found in the feed source for the production of ultrapure water (UPW), urea is challenging to remove because it is a small molecular weight molecule that is not easily oxidized and does not carry a charge under neutral pH conditions. Urease enzyme, found in various organisms such as plants and bacteria, catalyze the hydrolysis of urea into carbon dioxide and ammonia. In this study, urease was immobilized on the polyamide layer of a reverse osmosis (RO) membrane to remove urea in UPW systems. The removal efficiency of urea by urease-coated RO membrane showed up to 27.9 % higher urea removal efficiency compared to the pristine membrane. This increase in urea removal can be attributed to both physical and biological effects from the urease coating on the membrane. Firstly, urease on the membrane surface can act as an additional physical barrier for urea to pass through. Secondly, urea can be hydrolyzed by the enzyme when it passes through the urease-coated RO membrane. In a two-pass RO system typical for UPW production, the removal of urea by a urease-coated membrane would be enhanced by twofold. This overall method can significantly increase the removal efficiency of urea in UPW systems, especially when considering the compounded removal by the urease coating, rejection by RO, and additional reactions by other treatment processes. Moreover, urea in UPW systems can be removed without the installment of additional processes by simply coating urease on the existing RO membranes.

Ultrapure water production technology—Development of high-purity ion exchange resin—

Ultrapure water production technology—Development of high-purity ion exchange resin—

Monodispersed Co-N3 loaded carbon nitride mediated peroxymonosulfate activation for rapid degradation of trace urea via singlet oxygen

The removal of trace urea presents a significant challenge in the production of electronic-grade ultra-pure water (UPW). This study proposed a simple strategy to regulate the low-coordination of a single-atom cobalt catalyst (RyCo-CN0.20) for the efficient removal of trace urea via peroxymonosulfate (PMS) activation. The optimal R0.50Co-CN0.20 with low-coordination Co-N3 sites was constructed by in-situ reduction of NaBH4 and significantly enhanced the PMS activation. The removal efficiency of trace urea achieved 94 % within 5 mins. The kobs of trace urea degradation in R0.50Co-CN0.20/PMS system reached 0.4576 min−1, which was much higher than previous reported systems. Experiments of free radical quenching and electron paramagnetic resonance demonstrated that singlet oxygen species were the dominant free radical. The corresponding steady concentration of singlet oxygen species in the R0.50Co-CN0.20/PMS system was enhanced to be 16.361 × 10–6 μM, which was twice of Co-CN0.20/PMS. Density functional theory calculations revealed that the optimized electron distribution of the Co center in the Co-N3 sites processed a higher d band center (−1.08 eV) and richer electron transfer number (0.75 e−) compared with Co-N4 sites, hence realizing the stronger PMS activation. Continuous operation verified that R0.50Co-CN0.20/PMS could maintain the removal rate of trace urea above 80 % after 150 h operation. Moreover, R0.50Co-CN0.20/PMS in the pilot UPW production process effectively reduced the pollution caused by trace urea and ensured the quality of the terminal UPW (Total organic carbon <1 μg/L). This study provides a new approach for the removal of trace urea through PMS activation by low-coordination single-atom catalysts.

Fate of low molecular weight organic matters in reverse osmosis and vacuum ultraviolet process for high-quality ultrapure water production in the semiconductor industry

Ultrapure water (UPW) is essential in the semiconductor industry for rinsing and cleaning products. With the growing demand for UPW, various feed water sources such as tap water, surface water, and wastewater are utilized to produce UPW. However, these feed water sources contain various low molecular weight organic matters (LMWOMs), which can adversely affect the quality of semiconductors when present in treated UPW. Therefore, achieving the complete removal of LMWOMs is crucial in the UPW production process. However, the current reverse osmosis (RO) and vacuum ultraviolet (VUV) processes employed for UPW production have limitations in achieving complete LMWOM removal. Therefore, this study is conducted to investigate the mechanisms of LMWOM removal in RO and the performance of VUV for high-quality UPW production. Six LMWOMs found in the semiconductor industry were tested for lab- and pilot-scale experiments. The result showed that size exclusion is the main mechanism of LMWOM removal in the RO process. However, methanol, ethanol, and urea were not efficiently removed by RO membranes. In addition, a lab-scale VUV experiment was performed under accelerated conditions to examine the oxidation mechanism of LMWOM. The LMWOM with low reactivity to hydroxyl radicals, such as tetramethylammonium hydroxide (TMAH) and urea, were not removed perfectly within 60 min and 180 min, respectively. Furthermore, a pilot-scale VUV experiment was performed to examine the oxidation of LMWOM under real UPW production conditions. Despite observing a correlation in the pseudo-first-order rate constants between the lab-scale and pilot-scale experiments, the removal of TMAH and urea was still not achieved even with a lamp power of 320 W. As urea was not completely removed by either RO or VUV, strategies for UPW production using current water sources are discussed to develop future UPW technologies.

A Facile Ultrapure Water Production Method for Electrolysis via Multilayered Photovoltaic/Membrane Distillation

Ultrapure water production is vital for sustainable green hydrogen production by electrolysis. The current industrial process to generate ultrapure water involves energy-intensive processes, such as reverse osmosis. This study demonstrates a facile method to produce ultrapure water from simulated seawater using a low capital cost and low-energy-consuming membrane distillation (MD) approach that is driven by the waste heat from photovoltaic (PV) panels. To optimize the PV-MD operation, modeling efforts to design a multilayered MD system were carried out. The results were used to guide the construction of several prototype devices using different materials. The best performing PV-MD device, containing evaporation and condensation regions made from steel sheets and polytetrafluoroethylene (PTFE) membranes, can produce high-purity water with conductivity less than 40 mS and flux higher than 100 g/m2 h, which is suitable for typical electrolyzer use.

High recovery reverse osmosis design to minimize wastewater of ultra-pure water production process

High recovery reverse osmosis design to minimize wastewater of ultra-pure water production process

Biological Oxygen-dosed Activated Carbon (BODAC) filters – A bioprocess for ultrapure water production removing organics, nutrients and micropollutants

Biological oxygen-dosed activated carbon (BODAC) filters in an Ultrapure water plant were demonstrated to have the potential to further treat secondary wastewater treatment effluent. The BODAC filters were operated for 11 years without carbon regeneration or replacement, while still functioning as pre-treatment step to reverse osmosis (RO) membranes by actively removing organic micropollutants (OMPs) and foulants. In this study, the removal of nutrients and 13 OMPs from secondary wastewater treatment effluent was investigated for 2 years and simultaneously, the granules’ characterization and microbial community analysis were conducted to gain insights behind the stable long-term operation of the BODAC filters. The results showed that the BODAC granules' surface area was reduced by ∼70 % of what is in virgin carbon granules and covered by biofilm and inorganic depositions. The BODAC filters reduced the concentration of soluble organics, mainly proteins, performed as an effective nitrification system, and almost completely removed manganese. During the 2 years of observation, the filters consistently removed some OMPs such as hydrochlorothiazide, metoprolol, sotalol, and trimethoprim by at least 70 %. Finally, through microbial community analysis, we found that nitrifying and manganese-oxidizing bacteria were detected in high relative abundance on BODAC granules, supporting BODAC performance in removing OMPs and manganese as well as converting nitrogenous species in the water.

Urea removal for ultrapure water production by VUV/UV/chlorine under acidic aqueous conditions: Facile elimination and efficient denitrification

Urea in the ultrapure water production process threatens semiconductor manufacturing. This work proposed a urea removal strategy involving the VUV/UV/chlorine process in an acidic solution to achieve high-efficiency urea removal. VUV/UV/chlorine could thoroughly remove urea of 2 mg/L within 9 min at pH 3. A TN removal rate of 70% and a dissolved organic carbon removal rate of 84% were achieved in the urea degradation process. The decrease in pH and the increase in oxidant dosage could improve urea removal efficiency. The presence of chloride anion could improve urea removal by 55–85%. Based on the radical probe and quenching experiments, free radicals accounted for more than 90% of urea removal. •Cl2− and •OH were calculated to contribute approximately 36% and 22%, respectively, to urea removal. •Cl and •ClO together contributed less than 32%. The chlorination of urea was responsible for less than 10% of urea removal. Nitrogen in urea was transformed efficiently into inorganic nitrogen (N2, ammonium, and nitrate with a rough ratio of 6:1:1.1). Organic chlorine products formed in the urea degradation process took up less than 3% in all chlorine element and was converted into chloride anion finally.

A modified spectrophotometric method for selective determination of trace urea: application in the production process of ultrapure water

Abstract Conventional spectrophotometric methods were unable to accurately detect urea concentrations below 100 μg/L. A modified spectrophotometric method was developed to determine the trace urea in the ultrapure water (UPW) production process of the semiconductor manufacturing industry. This method was optimized based on the dosage of chemical agents, length of the optical path, and mode of the water bath. Metal ions were added to promote the stability of the chromogenic system. A calibration graph was observed with ideal linearity in the range of 0.8–100 μg/L. The detection and quantification limits of urea were 0.24 and 0.80 μg/L, respectively. The distribution of urea in raw water for the UPW production process was observed and the urea in tap water was 10–20 μg/L. The urea of municipal reclaimed water was 24–40 μg/L, which was twice that of industrial reclaimed water at 10–18 μg/L. The total removal rate of urea by the UPW production process was 50–70%. Reverse osmosis membranes played a critical role in the removal of urea (over 30%). The urea in the final UPW produced from tap water was approximately 4.1 μg/L, which creates a potential risk of excessive total organic carbon.

Modeling and optimization of electrodeionization process for the energy-saving of ultrapure water production

Electrodeionization (EDI) is essential for producing ultrapure water in power plants and high-tech industries. Compared with the traditional ion exchange process, EDI does not require high-pollution resin regeneration by acid and alkali reagents. However, the process is markedly energy-intensive, and thus it is crucial to reduce the energy consumption. The reduction may be achieved by optimizing the operating conditions and module design. Previous mathematical models of the EDI process have been based on the mass transfer mechanism of ion removal. However, the water dissociation reactions, which are crucial for the energy efficiency of ion removal and thus EDI optimization, have rarely been considered. In particular, the design of EDI modules has not been studied. In this study, the water dissociation reactions in the EDI model were considered to simulate the ion removal process and energy consumption. In addition, the design variables of the equipment configuration and the operating conditions of an industrial-scale EDI module were optimized to reduce the energy consumption via nonlinear programming. The results show that the energy consumption of the current industrial EDI operation can be reduced by 22.4% when only the operating conditions are optimized. Furthermore, the optimization of the design and operation, based on the annual cost, will lead to a 50.4% decrease in the annual cost. The developed modeling and optimization method will play a critical role in an energy-saving operation and low-cost design of the EDI process.