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In this work, a novel treatment module capable of simultaneously enacting electrocoagulation and electrofiltration was designed, fabricated, and tested aiming for the reclamation of CMP (chemical mechanical polishing) wastewater. In general, CMP wastewater contains sub-micron particles and has high alkalinity, turbidity, total solids content, and silica content. Discharge of CMP wastewater without proper treatment would pose a great threat to the environment and ecology. In this investigation, oxide CMP wastewater and mixed CMP wastewater were obtained from a wafer fab in Taiwan. They were characterized by various standard methods. In this study, the efficiency of this dual-function treatment module (using aluminum as the sacrificing anode and stainless steel as the cathode) was evaluated in terms of applied electric field strength (0 ~ 112.5 V/cm), influent velocity (112 ~136 cm/s), and transmembrane pressure (1.0 ~ 3.0 kgf/cm2) on permeate qualities. Experimental results have shown that the contents of total solids of permeates could be reduced to about 180 mg/L and 426 mg/L, respectively for oxide CMP wastewater and mixed CMP wastewater. The respective values of turbidity and total organic carbon could also be reduced to below 1 NTU and 1.5 mg/L. Therefore, the treated water could be reused as the feed water for the ultrapure water production system. In this study, an empirical equation was established to relate the quantity of filtrate and applied electric field strength when CMP wastewater was subjected to electrofiltration alone. It was found that the theoretical aluminum concentration released to the reaction chamber was much greater than the actual one. This would explain why the efficiency of electrocoagulation needs to be improved in this treatment module. Experimental results also have indicated that proper backflushing would be beneficial to the flux of permeate and saving of membrane cost.

In this study, nanosized TiO2-containing organic wastewater was treated with a simultaneous electrocoagulation/electrofiltration (EC/EF) process using either a recirculation mode or a flow-through mode. In the EC/EF treatment module, iron and stainless steel (SS 304) were respectively selected as the anode and cathode, and polyvinylidene fluoride (PVDF) with a nominal pore size of 0.1 £gm was used in this work. Applied electric field strength (EFS), transmembrane pressure (TMP), and crossflow velocity (CFV) were selected as the operating parameters for studying their effects on permeate qualities and other performance criteria. In the recirculation mode, the residual chemical oxygen demand (COD) was found to decrease with increasing EFS up to the critical EFS (i.e., 166.7 V/cm) and leveled off. The optimal operating conditions were determined to be an EFS of 166.7 V/cm, a TMP of 1 kgf/cm2, and a CFV of 0.22 cm/s. Under the optimal operating conditions, the removal efficiencies for turbidity, conductivity, total dissolved solids (TSD), and titanium were determined to be 98.7%, 95.1%, 95.8%, and 99.9%, respectively. By using the same operating conditions except in the flow-through mode, the corresponding removal efficiencies were found to be 98.1%, 92.3%, 93.1%, and 99.9%, respectively. Experimental results also showed that the flow-through mode yielded a higher filtration rate than that of the recirculation mode (namely, 5.05 mL/min versus 4.75 mL/min). This is an indication of a lower extent of membrane fouling for the flow-through mode. This was also evidenced by the scanning electron microscope (SEM) micrographs of the post-treatment membranes. In the recirculation mode, a proper practice of backflushing (e.g., a period of 60 min and a duration of 0.5 min) was found to extend the service life of the membrane and to enhance the permeate flux. I so doing, a minimum treatment rate of 90L/hr with a treatment cost of NT$68.10 per cubic meters would be resulted. Permeate obtained was found to meet the criteria of make-up water for cooling towers. Overall speaking, the simultaneous EC/EF treatment module employed in this work is capable of treating nanosized TiO2-containing organic wastewater for the purpose of reclamation.

In this work, membrane set(s) had been incorporated into different crossflow electrofiltration (CEF) /electrodialysis (ED) treatment modules for treating various CMP wastewaters and simultaneously generating two streams of electrolytic ionized water (EIW). In general, CMP wastewaters have high alkalinity, turbidity, total solids content and silica content. In this investigation, CMP wastewaters were obtained from two wafer fabs in Taiwan and characterized by various standard methods. Then they were treated by the aforementioned treatment modules. Experiments were carried out based on the fractional factorial design and the L8 orthogonal arrays of the Taguchi method. Experimental factors such as electric field strength, transmembrane pressure for CEF, etc. were used to investigate their effects on the permeate qualities (i.e., oxidation-reduction potential, pH, etc.). According to the results of analysis of normal probability plots, analysis of variance (ANOVA) and regular analysis, the electric field strength was presumed to be a very significant parameter. Experimental results showed that filtrate flux increased with the increasing applied electric field strength. The permeate has a turbidity of below 1 NTU, TOC of below 3 mg/L, and TDS of below 250 mg/L under various operating conditions. Other permeate qualities were 15~22 mg/L of K, 53~68 mg/L of silica, 2~4 mg/L of NH4+ and 134~680 £gS/cm of electrical conductivity. But the values of electrical conductivity, pH, and oxidation-reduction potential (ORP) varied substantially for the anolyte EIW and catholyte EIW. Using these novel treatment modules, the optimal ORP and pH values of the anolyte EIW were 211.8 mV, 4.52 and 214.1 mV, 4.83, respectively, for single- and multi-membrane sets. The optimal ORP and pH values of the catholyte EIW were -165.0 mV, 11.21 and -172.0 mV, 10.81, respectively, for single- and multi-membrane sets. It is clear that permeate obtained in this study is suitable for high-level recycling. To further upgrade the water quality of permeate obtained above, a reverse osmosis (RO) unit was added to the treatment system. The water quality of silica for post-RO permeate were decreased from 53.7 to 0.98 mg/L for the anolyte EIW and from 68.05 to 1.32 mg/L for the catholyte EIW. The removal rates of Na and K by the RO unit were not significant. In addition, other unique properties of EIW (e.g., pH, ORP, and cluster size of water molecules) remained almost the same in post-RO permeate. The total recovery rate of the treated water could be above 85%. Therefore, the treated water at this stage could be reused as the cleaning media for the wafer surfaces or reused for the DI water production apparatus.

A flux declination predication model for nanoparticle-containing wastewaters treated by a simultaneous electrocoagulation/electro- filtration (EC/EF) process was investigated by perceiving blocked membrane pores, concentration polarization layer, cake layer, and applied electric field strength in this study. As nanotechnology develops, it has been used in many applications. However, its environmental impacts have not been extensively studied. Membrane technology is one of the direct and effective treatment methods for removing nanoparticles from wastewater. But nanoparticle-containing wastewater treated by membrane technology would face the problem of membrane fouling. In this study, oxide chemical mechanical polishing (CMP) wastewater, copper CMP wastewater, and nanosized TiO2-containing wastewater were treated by a EC/EF treatment module. In the EC/EF treatment module, iron, aluminum, and stainless steel were respectively selected as th anode and cathode. Polyvinylidene fluoride (PVDF) with a nominal pore size of 0.1 £gm and carbon/Al2O3 tubular inorganic composite membranes with a pore size ranging from 2 to 10 nm were used in this work. In this work, the changes of the relevant performance of membrane with changes of applied pressure (9.8-19.6 kPa), crossflow velocity (0.3-0.5 m/s) and applied electric filed strength (25-233 V/cm) were studied. The simulation results of a modified mathematic model showed that the flux declination would be fitted finely by an exponential function. Experimental results showed that a higher transmembrane pressure would yield a higher cake concentration and a higher crossflow velocity would yield the steady flux quickly. Overall speaking, the flux declination for nanoparticle-containing wastewaters treated by a simulataneous EC/EF process was described properly as a exponential form. The exponential function could simply show the flux declination of different samples treated by different modules in different situations.

In this study, two types of chemical mechanical polishing wastewaters (designated Cu-CMP wastewater and mixed-CMP wastewater, respectively) from a wafer fabrication plant was treated by a simultaneous electrocoagulation/electrofiltration (EC/EF) process using laboratory-prepared TiO2/Al2O3 composite membranes. First, tubular membrane supports of Al2O3 were prepared by the extrusion method. Then the slip composed of nanoscale TiO2 (prepared by sol-gel process) and 1 wt% of corn starch was applied on the aforementioned tubular membrane supports by the dip-coating method, followed by sintering to obtain tubular TiO2/Al2O3 composite membranes. These tubular inorganic composite membranes then were incorporated into an EC/EF treatment module for the treatment of CMP wastewaters. The permeate qualities were evaluated. In addition, the effects of different operating modes (i.e., the flow-through mode and recirculation mode) on membrane flux and permeate quality were conducted. Finally, the effects of changing the backwash time and backwash cycle on the membrane flux were also investigated. Experimental results have shown that the slip containing 75 v/v% of TiO2 sol and 25 v/v% of corn starch solution would yield a membrane layer with a thickness of 13 £gm and a pore size of 15 nm. On the CMP wastewater treatment, the removal efficiencies of copper ion and total organic carbon (TOC) were found to increase with the increasing electric field strength. This relationship, however, did not apply to other water quality items. Under the optimal operating conditions of using the recirculation mode, the removal efficiencies for turbidity and TOC for Cu-CMP wastewater were determined to be 98% and 90%, respectively. Similarly, a turbidity of < 1 NTU (a removal efficiency of 99%) was obtained for mixed-CMP wastewater. By using the same optimal operating conditions for the recirculation mode to treat Cu-CMP wastewater, initial fluxes of 300 L/h¡Em2 and 280 L/h¡Em2 were obtained for the flow-through mode and recirculation mode, respectively. The corresponding initial fluxes for mixed-CMP wastewater were 370 L/h¡Em2 and 360 L/h¡Em2, respectively. For the case of the recirculation mode, the removal efficiencies of total solids content, silicon, copper ion, TOC, and turbidity for Cu-CMP wastewater were 71%, 85%, 72%, 90% and 99%, respectively. The corresponding removal efficiencies of 68%, 88%, 78%, 90% and 99%, respectively were determined for the case of the flow-through mode. On the other hand, the removal efficiencies of total solids content, silicon, TOC, and turbidity for mixed-CMP wastewater using the recirculation mode were 76%, 84%, 78% and 99%, respectively; whereas 78%, 86%, 72% and 99%, respectively for the flow-through mode. Based on the above findings, the operating mode is not a significant parameter in influencing the membrane flux and quality. Permeate obtained in this work was found to be recyclable for the use in irrigation and make-up water for cooling towers. Backwashing was found to be important to the membrane flux in this study.

Water is essential for life as well as industrial growth. Therefore, this research is mainly to explore the treatment capacity of LCD (Liguid Crystal Display) industrial wastewater recycling by a simultaneous electrocoagulation/electrofiltration (EC/EF) process using laboratory-prepared multi-tubular TiO2/Al2O3 composite membranes. First, tubular membrane supports of Al2O3 were prepared by the extrusion method. Then the slip composed of nanoscale TiO2 (prepared by sol-gel process) was applied on the aforementioned tubular membrane supports by the dip-coating method, followed by sintering to obtain tubular TiO2/Al2O3 composite membranes. Then, two types of LCD industrial wastewaters (designated TFT-LCD wastewater and STN-LCD wastewater, respectively) from different LCD fabrication plants were treated by EC/EF process using TiO2/Al2O3 composite membranes. Moreover, the permeate qualities were evaluated under the recirculation-mode operation. In addition, the effects of different operating parameters (i.e., electric field strength, trans-membrane pressure, and crossflow velocity) on membrane flux and permeate quality were evaluated. Relations of the water quality and the different operation modes (i.e., the recirculation mode, flow-through mode, and secondary treatment mode) were also discussed. Finally, the effects of changing the backwash time and backwash cycle on membrane flux were investigated. In the recirculation mode, both kinds of wastewater achieved a satisfactory organics and anion removal. An average of about 90¢H of COD (Chemical Oxygen Demand) and TKN (Total Kjeldahl Nitrogen) could be removed. For anions (i.e., NO3¡Ð, NO2¡Ð, Cl¡Ð and SO42¡Ð), their removal efficiencies were all over 90%. Furthermore, TOC (Total Organic Carbon) and turbidity also had removal efficiencies of over 98%. When the operation mode was changed from the recirculation mode to flow-through mode, the changes of permeate quality were not obvious. But the cumulative quantity of permeate of the flow-through mode was greater than that of the recirculation mode. As for the experimental result of the secondary treatment mode, the permeate qualities were found to be improved. In this case, an average removal of over 95% of NO3¡Ð, NO2¡Ð, Cl¡Ð, and SO42¡Ð could be obtained. According to experimental results shown above, the treated water could be recycled and reused as the cooling tower make-up water if its pH and conductivity values were reduced. However, these problems could be easily resolved by proper adjustments of pH. Overall speaking, the tubular TiO2/Al2O3 composite membranes and simultaneous EC/EF treatment module employed in this work are capable of treating LCD industrial wastewater for the purpose of reclamation.

Arsenic and perchlorate are two types of emerging contaminants commonly found in various water bodies worldwide. Therefore, the development of effective removal technologies has become an important issue today. To this end, the following research studies were conducted. First, trimethylchlorosilane (TMCS) was used for the surface modification of a laboratory-prepared outside-in tubular TiO2/Al2O3 composite membrane aiming at enhancing the filtration performance of the said membrane layer. Second, the TMCS-modified tubular ceramic membrane coupled with the simultaneous electrocoagulation/ electrofiltration (EC/EF) process was tested and evaluated their combined performance in the remediation of arsenic- and perchlorate-spiked waters and one actual As-contaminated groundwater. In this research, the results of a preliminary electrocoagulation study have indicated that aluminum outperformed iron as the anode material. Thus, aluminum was selected as the sacrificial anode for the EC/EF tests throughout this work. In the course of various EC/EF testing, the removal efficiencies of the target contaminant in the test water specimens were compared for the tubular TiO2/Al2O3 composite membranes with and without surface modification. Also evaluated included the permeate flux, unit mass of target contaminant removed, and relevant power consumption. Though surface modification might not yield a better removal efficiency of the concerned contaminant, it gave rise to a greater permeate flux resulting in a greater removed mass of the contaminant for each of the synthetic wastewaters. Meanwhile, lower power consumption was found as compared with the case of no surface modification. As for the actual As-contaminated groundwater, the optimal EC/EF conditions for the tubular composite membrane without surface modification could low the As concentration to meet the local irrigation water quality criteria.

Water recycling has become a global trend because of water scarcity and increased demand of water supply. Therefore, attentions to the improvement of reclaimed water quality have been paid. In the past decade various environmental hormones and PPCPs (pharmaceuticals and personal care products) have been detected in different aquatic environments. Even though their concentrations are in the range of ng/L to £gg/L, these emerging contaminants might cause harm to human health and the environment. Nanoscale contaminants are another type of emerging contaminants cannot be neglected because many nanomaterials have been used in household goods of our daily lives. Thus, how to effectively separate and/or recover those nanomaterials from aqueous solution to reduce their potential hazards is an important issue The first objective of this study was to assess the efficiency of nano-Fe3O4/S2O82- oxidation against selected environmental hormones (i.e., di(2-ethylhexyl)phthalate (DEHP) and perfluorooctane sulphonates (PFOS)) and pharmaceuticals (i.e., erythromycin (ERY) and sulfamethoxazole (SMX)) in aqueous solution. The optimal operating conditions obtained from the above-indicated oxidation process were then transferred to a simultaneous electrocoagulation and electrofiltration (EC/EF) treatment module into which a tubular TiO2/Al2O3 composite membrane was incorporated. The purpose of this practice was to evaluate whether the EC/EF process could further enhance the removal of target contaminants. In this work nanoscale magnetite (nano-Fe3O4) used for activation of S2O82- oxidation was prepared by chemical coprecipitation. Then, X-ray powder diffractometry was used to confirm the crystal structure of the prepared particles as magnetite. The employment of 3 wt% soluble starch was found to be sufficient to stabilize nano-Fe3O4 for later uses. Further, slurries of nano-Fe3O4 and S2O82- (sodium persulfate) were prepared with three dosage ratios, namely 1:2.5, 1:5 and 1:10. Nano-Fe3O4/S2O82- slurries thus prepared were used for evaluating their efficiencies in removing target contaminants (i.e., DEHP, PFOS, ERY, and SMX) of two concentration levels. In this study the high concentration level referred to 38 mg/L for DEHP and 10 mg/L each for the rest of target contaminants, whereas 10 £gg/L as the low concentration level for each of target contaminants. Batch experiments of nano-Fe3O4/S2O82- oxidation against target contaminants were first carried out in glass beakers. In the case of high concentration level with a nano-Fe3O4-to-S2O82- dosage ratio of 1:10, the respective removal efficiencies for all target contaminants were greater than 98%. Using the same dosage ratio for the case of low concentration level, however, the respective removal efficiencies for all target contaminants decreased to 78-91% except for ERY. When all target contaminants of low concentration level co-existed in the reaction vessel, the residual concentrations of environmental hormones were found to be greater than that of pharmaceuticals. Under the circumstances, the removal efficiency of DEHP dropped to 70% or so. The reaction pathways of nano-Fe3O4/S2O82- oxidation against each of target contaminants with a high concentration level were also investigated. The degradation intermediates detected for all target contaminants were all in line with the literature. Besides, the degradation intermediates were all close to their respective end products except those originated from DEHP. In other words, nano-Fe3O4/S2O82- per se had a phenomenal oxidation rate against each target contaminant. The performance of EC/EF-assisted nano-Fe3O4/S2O82- oxidation against target contaminants of low concentration level was also evaluated in this study. In each test every contaminated aqueous solution was physically preconditioned within the EC/EF treatment module for 20 min prior to the application of an electric field to enact electrocoagulation and electrofiltration. The optimal operating conditions obtained were given as follows: aluminum anode, electric field strength of 60 V/cm, transmembrane pressure of 98 kPa, and crossflow velocity of 3.33 cm/s. Under such conditions, the removal efficiencies for DEHP, PFOS, ERY, and SMX were determined to be 95%, 99%, 100%, and 99%, respectively. In the case of mixed environmental hormones and pharmaceuticals, the respective removal efficiencies slightly decreased to 85-99%. It is evident that the coupling of the EC/EF process with nano-Fe3O4/S2O82- oxidation yielded a substantial removal increase for selected target contaminants. Additionally, in all tests of EC/EF-assisted nano-Fe3O4/S2O82- oxidation against target contaminants, no residual nano-Fe3O4 was found in permeate. After a simple adjustment of pH, permeate thus treated would be ready for reuse in cooling towers.

This study addresses three major parts: (1) to establish the technology for the preparation of tubular ceramic membrane substrates; (2) to establish the technology for the preparation of tubular carbon/ceramic membranes; and (3) to reclaim water from chemical mechanical polishing (CMP) wastewaters by a combined treatment system of a novel simultaneous electrocoagulation/electrofiltration (EC/EF) process coupled with laboratory-prepared tubular composite membranes (TCMs) and evaluate its feasibility of water recycling and operating cost. First, in this work the green substrates of tubular porous ceramic membranes consisting of corn starch were prepared using the extrusion method, followed by curing, drying, and sintering processes. Experimental results have demonstrated that an addition of starch granules to the raw materials would increase the porosity, pore size, and permeability of the sintered matrices but accompanied by a decrease of the compressive strength. It revealed that the membrane substrates with desired pore sizes and permeability could be obtained by adding a proper amount of corn starch. The nominal pore sizes of the prepared membrane substrates were ranging from 1 to 2 £gm. The membrane substrates thus obtained are suitable for crossflow microfiltration applications. Second, the carbon/alumina TCMs and carbon fibers/carbon/alumina TCMs were obtained by the chemical vapor deposition (CVD) method resulting in a pore size distribution of 2 to 20 nm and a nominal pore size ranging from 3 to 4 nm. Besides, during the CVD process the reaction temperature was found to be the main factor for influencing the pore size of carbon fibers/carbon/alumina TCMs and the type of carbon fibers. When the reaction temperature was above or equal to 1000 ¢J, the pore size of TCMs increased due to the pyrolysis of thin carbon layers. The ¡§Tip-Growth¡¨ mechanism was found for tubular carbon fibers formation under such conditions. On the other hand, ¡§Base-Growth¡¨ (also known as ¡§Root-Growth¡¨) mechanism was found for curved and irregular carbon fibers formation when reaction temperature was under or equal to 950 ¢J. Third, for reclaiming water from CMP wastewaters, experimental results of laboratory-prepared carbon/alumina TCMs incorporated into the custom-made EC/EF treatment module used was found to be capable of treating oxide-CMP wastewater in a proper manner. Permeate thus obtained had a turbidity of below 0.5 NTU and the removal efficiencies of TS (total solids content) and Si were 80% and 93 %, respectively. Further, for understanding the applicability of fractional factorial design and Taguchi experimental design, two laboratory-prepared carbon fibers/carbon/alumina TCMs (i.e., Tube B and Tube E obtained from two different preparation conditions) incorporated into the EC/EF treatment module were chosen for evaluating the performance of CMP wastewaters treatment. Permeate obtained based on the fractional factorial design of experiments had a turbidity of below 1.0 NTU and the removal efficiencies of TOC (total organic carbon), Cu and Si were all above 80 % except for the TS (i.e., ranging from 72 to 74%). Permeate obtained based on the Taguchi experimental design had a turbidity of below 0.3 NTU and the removal efficiencies of TS, TOC, Cu and Si were ranging from 82 to 91%. Apparently, similar optimum operating conditions were obtained from the fractional factorial design and Taguchi experimental design. Permeate thus obtained could be reused as the make-up water of cooling towers. The operating cost of Cu-CMP wastewater treatment based on a total water reclaim of 600 m3 per day was determined to be NT$ 98 (i.e., US$ 3.22) and NT$ 35 (i.e., US$ 1.05) per m3 of permeate for Case 1 (i.e., the filtration area of 0.0189 m2 in one EC/EF module) and Case 2 (i.e., the filtration area of 0.0801 m2 in one EC/EF module), respectively.