Chemical Mechanical Polishing Wastewater Research Articles

Improvement of Coagulation and Membrane Filtration Performance in Hybrid Coagulation-UF-RO System for Chemical Mechanical Polishing Wastewater Treatment: Effect of Coagulants

Improvement of Coagulation and Membrane Filtration Performance in Hybrid Coagulation-UF-RO System for Chemical Mechanical Polishing Wastewater Treatment: Effect of Coagulants

Role of co-existing ions in the removal of dissolved silica by ceramic nanofiltration membrane

Even low concentrations of nano-sized silica particles should be effectively removed from chemical mechanical polishing (CMP) wastewater as they can corrode the pipes in semiconductor manufacturing processes. In this study, we systematically investigated the factors affecting the silica removal efficiency using ceramic nanofiltration (NF) membranes under different conditions to remove nano-sized dissolved silica, which is difficult with conventional microfiltration (MF) or ultrafiltration (UF) membranes. A tubular ceramic NF membrane with an average pore size of approximately 946 Da (≈1.3 nm) was strongly negatively charged at pH values above 4.0, indicating the existence of repulsive forces between the membrane and monoanionic silica (H3SiO4−) under basic pH conditions. As the pH level increased from 4 to 12, retention increased from 10.6 % to 62.0 %, and it also increased with increasing concentration of dissolved silica and applied pressure. We also investigated the effect of combined salt solutions (KCl, K2SO4, CaCl2, or CaSO4) on the removal efficiency for dissolved silica to better understand the mechanism for underlying the operating conditions. When dissolved silica was the only contaminant in the solution, 61.6 % was removed however, the presence of cations such as Ca2+ with higher valence reduced the removal efficiency by up to 20.5 %. The presence of calcium compounds that bonded to higher-valence anions had a greater impact on the removal efficiency for dissolved silica. Our findings can serve as guidance for the selection of suitable coagulants and the improvement of the membrane performance through fine control strategies in semiconductor wastewater treatment processes.

Investigating the fouling potential of the metal‐silicate complex on membrane by response surface method (RSM)

AbstractBACKGROUNDTo optimize the filtration efficiency of membrane systems for chemical mechanical polishing (CMP) wastewater, the fouling potential of silica, aluminum‐silicate complex, and copper‐silicate complex was investigated by the response surface method.RESULTSThe mathematical models for three kinds of fouling were successfully developed based on the SDI0.1μm‐1atm and MFI0.1μm‐1atm to describe the fouling potential. These models indicate that the metal‐silicate complex fouling was severe at a neutral pH. Moreover, the models reveal that the effect of metal ions on fouling potential is significant. Compared with the feed solution conditions of 500 mg SiO2 /L and pH 7.5, when 1 and 5 mg Al3+/L are added, the MFI0.1μm‐1atm values increase by 109% and 156%, respectively. In addition, when 1 and 5 mg Cu2+/L are added, the MFI0.1μm‐1atm values increase by 210% and 313%, respectively.CONCLUSIONThe decrease in filtration efficiency was in the order of copper‐silicate complex > aluminum‐silicate complex > silica. Therefore, the fouling potential increased significantly when the influent contained trace metal ions (Al3+ or Cu2+) at a near‐neutral pH, demonstrating the importance of managing pH and metal ions in CMP wastewater for membrane systems. In addition, the MFI0.1μm‐1atm is more suitable than the SDI0.1μm‐1atm for evaluating fouling potential. The SDI0.1μm‐1atm has limited value and a narrow range for fouling potential measurement. In contrast, the MFI0.1μm‐1atm is more sensitive and has a more comprehensive detection range. © 2023 Society of Chemical Industry (SCI).

Linkage of pipeline blockage to coagulation-flocculation process: effect of anionic polymer and pH

This study investigated the frequent blockages observed in the discharge pipeline in the chemical mechanical polishing wastewater treatment plant. Preliminary analyses indicated that blockages were predominantly consisted of residual organically-bounded Al due to overdosage of polyaluminum chloride (PACl) and anionic polymer during coagulation-flocculation process. To minimize the recurrence of blockage, jar test experiments were conducted in this study to identify optimum dosages of PACl and anionic polymer as well as optimum pH value. According to the model derived from jar tests, the optimum PACl dosage was dependent on the soluble Cu concentration of wastewater with low initial turbidity [< 1000 nephelometry turbidity units (NTU)]. The PACl dosage would require more than 5 mg L−1 when soluble copper below 20 mg L−1, while PACl is not necessary when more than 20 mg L−1 of soluble copper in the wastewater. On the other hand, optimal PACl dosage was dependent on the initial turbidity of wastewater with high initial turbidity (> 1000 NTU), while the optimal PACl dosage was 30 mg L−1 when initial turbidity around 7000 NTU. The change of pH in the range of 8 to 9.5 did not significantly affect the turbidity or Cu removal, however, higher pH increased the deposition of residual monomeric Al species which might lead to blockage. In summary, controlling PACl dosage at optimum dosage under the conditions of pH 8.5 ± 0.5 and 1 mg L−1 polymer could reduce the blockage occurrence as well as maintain the effluent quality to meet the standards.

Investigation of fluoride and silica removal from semiconductor wastewaters with a clean coagulation-ultrafiltration process

Fluoride and silica contamination in water is a worldwide issue due to the wastewater discharge from semiconductor industry. Coagulation-ultrafiltration (UF) process is commonly used to treat semiconductor wastewaters, but it requires excessive amounts of coagulant/flocculant. In this study, a clean coagulation-UF process using chemical mechanical polishing (CMP) wastewater as a coagulant to treat fluoride-containing wastewater was firstly proposed. The fluoride-containing wastewater, CMP wastewater, mixed fluoride-containing wastewater and CMP wastewater, and mixed fluoride-containing wastewater and polyaluminium chloride/polyacrylamide were compared to investigate turbidity removal efficiency, fluoride removal efficiency and membrane fouling resistance. The negatively charged SiO2 particles in CMP wastewater were found to be adsorbed on the positively charged CaF2 particles surface through electrostatic interaction. Results indicated that CMP wastewater provided a superior turbidity removal efficiency and a minimal membrane fouling resistance compared to conventional coagulant. After UF filtration, the fluoride concentration and turbidity were 2.09 mg L−1 and 0 NTU, respectively, which met the median fluoride effluent standard. The extended Derjaguin-Landau-Verwey-Overbeek theory showed that increasing molar ratio of SiO2 to CaF2 improved the interfacial free energy between membrane and suspended particles, thus mitigating membrane fouling. This clean design principle and strategy will broaden the sustainability of coagulation-UF process for wastewater treatment.

Treatment of semiconductor-industry wastewater with the application of ceramic membrane and polymeric membrane

There is an abundance of wastewater produced by the semiconductor industry. These wastewaters can be hazardous to the environment if they are discharged without treatment. Furthermore, they contain silicon residues that can be recovered and recycled. Though membrane technologies have the potential to recover the silicon while treating wastewaters, fouling remains a major obstacle. This study thus aims to evaluate the performance of commercial ultrafiltration (UF) ceramic and polymeric membranes in treating three types of semiconductor-industry wastewaters; diluted back grinding wastewater (DBGW), diluted chemical mechanical polishing wastewater (DCMPW), and collection tank wastewater (CTW). One type of ceramic membrane and two types of polymeric membranes were evaluated. The ceramic membrane achieved the highest permeate flux (131.23–308.98 L/m2h) for all three types of wastewaters and was least susceptible to fouling as indicated by the lowest relative flux reduction (RFR) (8.22–57.59%) due to its high porosity, hydrophilicity, and permeability. Irreversible fouling on the ceramic membrane can be mitigated by alkaline cleaning agents to regain flux during DCMPW (96.93%) and DBGW (53.80%) filtration. Acidic agents should be used to regain flux during CTW (79.54%) filtration. Silicon retained on the membrane had a high purity of 39.8 wt% as evidenced by the X-ray spectrometer (EDX) results. The long-term applications of ceramic and polymeric membranes for silicon recovery and wastewater treatment via various cleaning methods were therefore covered in this study.

Approaches to Sustainability in Chemical Mechanical Polishing (CMP): A Review

Chemical mechanical polishing (CMP) is an essential planarization process for semiconductor manufacturing. The application of CMP has been increasing in semiconductor fabrication for highly integrated devices. Recently, environmental burden caused by the CMP process was assessed because of interest in the global environment. In this study, the previously reported impacts of CMP on the environment and studies conducted on developing various methods to reduce environmental burden are reviewed. In addition to analyzing the impacts of CMP, this paper introduces a method for treating CMP wastewater and improving the material removal efficiency through the improvement of CMP consumables. Finally, the authors review research on hybridization of the CMP process and discuss the direction in which CMP technology will progress to improve sustainability in the future.

Remediation of cobalt from semiconductor wastewater in the frame of fluidized-bed homogeneous granulation process

Green and sustainable strategies aim for the development of manufacturing processes that maximize the use of resources, instigating the semiconductor industry to adopt zero-liquid discharge policies. Complexity and variations in semiconductor wastewater effluents open an opportunity for resource recovery. One such opportunity is the potential recovery of heavy metals such as cobalt and/or copper in chemical-mechanical polishing wastewater, and inorganic anions such as phosphate from etching and acid cleaning. The present work demonstrates the capabilities of homogeneous crystallization in fluidized-bed reactor as treatment technology to process water effluents for industrial reuse while simultaneously recovering precious resources such as copper, cobalt and phosphate. Experimental results revealed that the optimum conditions were achieved at effluent pH of 7.75 – 8.0 and [PO4−3]/[Co2+] of 2.0. Uniform crystal growth was attained due to appropriate fluidization and proper collision of the particles at up flow velocity 40.11 m h−1 with 1.18 kg Co2+ m−2 h−1 loading. Performance was based on the removal/recovery capabilities of cobalt as heavy metal pollutant. The percentage of total cobalt recovered by granulation was 98.8%, whereas 99% cobalt removal was attained at optimal parameters. Coexistence of EDTA and citrate inhibits crystal growth, decreasing the metal granulation capability ~35%. Mixing of copper and cobalt ions in fluidized-bed homogeneous crystallization process was also investigated in which the highest granulation of 95.9% was attained at effluent pH of 6.50 for copper, and 96.8% at effluent pH of 7.50 for cobalt with an equimolar metal concentration of 7.0 mM and phosphate-metal molar ratio of 1.60. The granules recovered were analyzed using XRD and SEM-EDS. The recovered crystals were identified as mineral libethenite (Cu2(PO4)OH) and cobalt phosphate hydrate (Co3(PO4)2.8H2O).

Dead-end and crossflow ultrafiltration process modelling: Application on chemical mechanical polishing wastewaters

Dynamic simulation of ultrafiltration process is applied to the treatment of chemical mechanical polishing wastewater from microelectronic industry. The ultrafiltration of nanoparticles (NPs) contained in chemical mechanical polishing wastewater is modelled by using different mathematical equations, which are derived from the literature and optimized to the effluent and filtration modes (dead-end or crossflow). A series of ultrafiltration experiments at laboratory scale are carried out by using chemical mechanical polishing wastewater to optimize and validate the models. Complete dead-end and crossflow ultrafiltration models are developed to simulate the treatment performances of chemical mechanical polishing wastewater under dynamic full-scale and different operating conditions, thus including filtration and washing steps. Simulations show that the dead-end mode is not suitable for chemical mechanical polishing wastewater concentration higher than 100mgNPsL−1 due to the too fast fouling time and to the high frequency of washing step. The high concentration of chemical mechanical polishing P wastewater (2600mgNPsL−1) forces industries to use crossflow ultrafiltration to have a profitable process by controlling parameters such as the filtration/backwashing number of cycles, the needed filtering surface and the filtration flux.

Agglomeration of Silicon Dioxide Nanoscale Colloids in Chemical Mechanical Polishing Wastewater: Influence of pH and Coagulant Concentration

Chemical mechanical polishing (CMP) wastewater generated from semiconductor manufacturing industries is known to contain residual organic and inorganic contaminants, i.e. photoresists, acids, including silicon dioxide (SiO&lt;sub&gt;2&lt;/sub&gt;), nanoparticles (NPs) and others. Nanoscale colloids in CMP wastewater have strong inclination to remain in the suspension, leading to high turbidity and chemical oxygen demand (COD). Although various types of pre-treatment have been implemented, these nanoparticles remain diffused in small clusters that pass through the treatment system. Therefore, it is crucial to select suitable pH and coagulant type in the coagulation treatment process. In this research zeta potential and dynamic light scattering measurements are applied as preliminary step aimed at determining optimum pH and coagulant dosage range based on the observation of inter particle-particle behavior in a CMP suspension. The first phase of the conducted study is to analyze nanoscale colloids in the CMP suspension in terms of zeta potential and z-average particle size as a function of pH within a range of 2 to 12. Two types of coagulants were investigated - polyaluminum chloride (PACl) and ferrous sulfate heptahydrate (FeSO&lt;sub&gt;4&lt;/sub&gt;·7H&lt;sub&gt;2&lt;/sub&gt;O). Similar pH analysis was conducted for the coagulants with the same pH range separately. The second phase of the study involved evaluating the interaction between nanoscale colloids and coagulants in the suspension. The dynamics of zeta potential and corresponding particle size were observed as a function of coagulant concentration. Results indicated that CMP wastewater is negatively charged, with average zeta potential of -59.8 mV and 149 d.nm at pH value of 8.7. The interaction between CMP wastewater and PACl showed that positively charged PACl rapidly adsorbed colloids in the wastewater, reducing the negative surface charge of nanoscale clusters. The interaction between CMP wastewater and FeSO&lt;sub&gt;4&lt;/sub&gt;·7H&lt;sub&gt;2&lt;/sub&gt;O showed that larger dosage is required to aggregate nanoscale clusters, due to its low positive value to counter negative charges of CMP wastewater.

Characterisation of nano-sized particles in chemical mechanical polishing wastewater

Treatment of chemical mechanical polishing (CMP) wastewater and fluoride-containing wastewater in semiconductor manufacturing are conventionally separated. The combined treatment of these two streams of wastewater was studied in terms of zeta potential and z-average hydrodynamic diameter profiles as a function of pH 2 to 12. Optimum pH for CMP wastewater was at pH 6 with zeta potential value of −10 mV and mean particle size of 180 d.nm. Meanwhile, for fluoride-containing wastewater the optimum pH obtained was at pH 9 with zeta potential of 10 mV and mean particle size of 5,214 d.nm. These two streams were combined together at their respective optimum pH and resulted a zeta potential value of 0.55 mV and mean particle size of 12,590 d.nm. Results indicated that the combined treatment for both polishing and fluoride-containing wastewater were beneficial as a larger flocs of fluorosilicate 26(SiF62−) was generated without the presence of coagulation chemicals. It is proposed that positively charged particles present in fluoride-containing wastewater become adsorbed on the surface of silica nanoparticles in CMP wastewater in which act as nuclei and enhances flocculation since repulsive force of both wastewater is decreased.

BS12-assisted flotation for the intensification of SNPs separation from CMP wastewater using a novel flotation column

In view of the extremely small size, high stable dispersion and intricate colloidal nature of silica nanoparticles (SNPs) in chemical mechanical polishing (CMP) wastewater, they might not only have hazards for environment and human health, but also cause low separation efficiency by classical water-treatment processes. Thus, it would be an important challenge to develop an efficient flotation technology for the separation SNPs. For this propose, this paper firstly presented the interaction between SNPs and dodecyl dimethyl betaine (ambient-friendly surfactant). Secondly, a novel flotation column was developed for strengthening interfacial adsorption by micro-bubbles and enhancing foam drainage by internal of regular-decagonal hollow frustum (RHF). One vital finding was that the mixture of micro-bubbles and macro-bubbles was conducive to improving the flotation performance. Under the suitable operating conditions, the enrichment ratio (E) and recovery percentage (R) of SNPs could reach 30.4±1.5 and 90.8±4.5%, respectively. The great E and R were obtained simultaneously, revealing a good participation of RHF in the flotation. Without a doubt, owing to the low chemical reagent addition and the high flotation performance, it was clear that our flotation has huge implications for the separation of nanoparticles from their wastewaters.

Using experimental design for the screening and optimization of key factors on silica particles adsorption using magnetic nanoparticles – a case study of chemical mechanical polishing wastewater treatment

This study applied magnetic nanoparticles (MNPs) to chemical mechanical polishing wastewater treatment using experimental design (Plackett–Burman methods) to select the key factors among pH, mixing, Polyaluminum chloride dosage, settling time, MNPs dosage, and temperature and using response surface methodology (RSM) to determine the optimal values of key factors. Research results showed that the key factors influencing processing performance were pH and rpm, and the optimal conditions were a pH of 4.9 and rpm of 68. The turbidity removal rate through RSM simulation was 90%; under this parameter, the actual turbidity removal rate in the experiment was 89%, which was extremely close to the simulation value; this value was also much higher than the nonoptimized removal rate of 61 ± 8%. Additionally, in the subsequent regeneration and reuse experiment involving mixing and ultrasound for desorption and regeneration, the number of recoveries were 4 and 5, respectively. The study showed that the average particle size of MNPs following ultrasonic vibration was reduced; the effect was optimal at 23 to 15 nm. Therefore, a removal rate of over 80% could be maintained for the fifth ultrasonic regeneration, and the energy of the mixing method may not have been sufficient, causing incomplete desorption and a turbidity removal rate of only 71%.

The effects of magnetic nanoparticles embedded with SA/PVA and pH on chemical-mechanical polishing wastewater and magnetic particle regeneration and recycle

Experiments were conducted using sodium alginate (SA) and polyvinyl alcohol (PVA) as embedded materials for Fe3O4 magnetic nanoparticles (MNPs). The materials provided excellent protection to the embedded MNPs in low-pH conditions. This study observed and compared the adsorption capacity of the unaltered and embedded MNPs. At pH 3 and without additional magnetic fields, the wastewater turbidity removal rate of the embedded MNPs reached a maximum of 95%, similar to that of the unaltered MNPs. Moreover, this study examined the recyclability and reusability of the unaltered and embedded MNPs and discovered that the embedded MNPs could be reused up to seven times. Overall, the use of SA/PVA prevented MNPs from disintegrating and contaminating the wastewater through the dissolution of Fe ions. SA and PVA also increased the reusability of the unaltered MNPs.

Particle removal performance and its kinetic behavior during oxide-CMP wastewater treatment by electrocoagulation

The treatment of chemical mechanical polishing (CMP) wastewater was investigated using the electrocoagulation (EC) method with a focus on its particle removal efficiency and kinetic behavior. The sacrificial electrode for use in the EC treatment was made of Fe, in which the supporting electrolytes of Fe2+ can be electrolytically generated. Several significant factors including pH, aeration and current density of the treatment system were evaluated. The experimental results showed that the pH controlled at 5 ∼ 7 after the EC treatment is preferable and applying aeration during the EC is effective for enhancing the particle removal efficiency. In this system, the particle removal efficiency was found to achieve 99% by treating the wastewater at a current density 5.9 mA/cm2 in 10 mins. Furthermore, a kinetic reaction model considering the charge neutralization and particle coagulation was proposed to describe the particle removal mechanism. The calculated result based on the model showed good agreement with the experimental data. It was also found that the reaction orders for the particle and Fe2+ concentration terms in the proposed particle removal rate equation are 2 and 4, respectively.

Purification of Chemical Mechanical Polishing Wastewater via Superconducting High Gradient Magnetic Separation System with Optimal Coagulation Process

This study examined the purification of wastewater from the chemical mechanical polishing (CMP) process via a superconducting high gradient magnetic separation (HGMS) system. To remove silica, the main contaminant in CMP wastewater, the optimal coagulation process of silica-magnetite-ferric hydroxide aggregates was empirically determined. Filtration tests via superconducting HGMS system with optimal coagulation process were conducted with respect to the magnetic field and wastewater flow rate. The turbidity and Si concentration of the wastewater filtered at 2 T and 400 mL/min were in accordance with the grey water standard and reverse osmosis (RO) feed water requirement, which demonstrated the feasibility of the superconducting HGMS system for the purification of CMP wastewater.

Adsorption treatment of oxide chemical mechanical polishing wastewater from a semiconductor manufacturing plant by electrocoagulation

In this study, metal hydroxides generated during electrocoagulation (EC) were used to remove the chemical oxygen demand (COD) of oxide chemical mechanical polishing (oxide-CMP) wastewater from a semiconductor manufacturing plant by EC. Adsorption studies were conducted in a batch system for various current densities and temperatures. The COD concentration in the oxide-CMP wastewater was effectively removed and decreased by more than 90%, resulting in a final wastewater COD concentration that was below the Taiwan discharge standard (100 mg L −1). Since the processed wastewater quality exceeded the direct discharge standard, the effluent could be considered for reuse. The adsorption kinetic studies showed that the EC process was best described using the pseudo-second-order kinetic model at the various current densities and temperatures. The experimental data were also tested against different adsorption isotherm models to describe the EC process. The Freundlich adsorption isotherm model predictions matched satisfactorily with the experimental observations. Thermodynamic parameters, including the Gibbs free energy, enthalpy, and entropy, indicated that the COD adsorption of oxide-CMP wastewater on metal hydroxides was feasible, spontaneous and endothermic in the temperature range of 288–318 K.

Performance of COD removal from oxide chemical mechanical polishing wastewater using iron electrocoagulation

This study investigated the feasibility of chemical oxygen demand (COD) abatement from oxide chemical mechanical polishing (oxide-CMP) wastewater. The process variables, including applied voltage, electrolyte concentration and temperature, were evaluated in terms of COD removal efficiency. In addition, the effects of applied voltage, supporting electrolyte, and temperature on electric energy consumption were evaluated. Under the optimum balance of variables, satisfactory COD removal efficiency and relatively low energy consumption were achieved. The optimum electrolyte concentration, applied voltage, and temperature were found to be 200 mg/L NaCl, 20 V, and 25°C, respectively. Under these conditions, the COD concentration in oxide-CMP wastewater decreased by more than 90%, resulting a final wastewater COD concentration that was below the Taiwan discharge standard (100 mg/L). Since the processed wastewater quality exceeded the direct discharge standard, the effluent could be considered for reuse. COD removal rates obtained during the electrocoagulation process can be described using a pseudo-kinetic model. The present study results show that the kinetic data fit the pseudo first-order kinetic model well. Finally, the morphology and composition of the sludge produced were characterized using scanning electron microscopy (SEM) and energy dispersion spectra (EDS).

Removal of fluoride from photovoltaic wastewater by electrocoagulation and products characteristics

Efficient treatment of fluoride-containing wastewater efficiently has been important for environmental engineers in Algeria. An appropriate concentration of fluoride in drinking water is required to prevent dental cavities, but long-term ingestion of water that contains more than a suitable level of fluoride causes bone disease and mottling of the teeth. The CMP wastewater from a UDTS. was characterized by high suspended solids (SS) content, chlorates, hydroxylamine, high turbidity (NTU), chemical oxygen demand (COD) concentration up to 7.00 mgl-1 and fluoride concentration up to 1000 mgl-1. Currently, the cheapest way to remove fluoride from semiconductor wastewater is to produce calcium fluoride (CaF2) by adding lime or another calcium salt. The aim of this paper is to propose an efficient and low cost treatment of chemical mechanical polishing wastewater process based on electrocoagulation with iron bipolar electrodes. The performance of a pilot scale electrochemical reactor equipped with iron bipolar ...

Chemical evidences for the optimal coagulant dosage and pH adjustment of silica removal from chemical mechanical polishing (CMP) wastewater

The coagulation behavior of aluminum salts in SiO 2(s)-containing chemical mechanical polishing (CMP) wastewater was investigated using jar tests and with reference to the coordination chemistry of Al(III) and Si(IV). The results of the jar tests show that the alum dosage did not influence the removal of silica when more than a particular amount of coagulant was added. However, the removal efficiency of the CMP wastewater depended more strongly on pH than on coagulant dosage. Insight into these results was given by the surface complexation model/surface precipitation model (SCM/SPM) and electrophoresis measurements. Simulation results thus obtained demonstrate that the Al(III) released from the coagulant underwent a two-stage reaction in a narrow range of 1.5 pH under under-saturated solution conditions with respect to the Al-hydroxide solid phase. At low pH (3.5–4.3), the Al(III) prevents the natural dissolution of SiO 2(s) particles by forming bi-nuclear surface complexes which energetically disfavor the simultaneous removal of two metal centers. In the pH range 4.3–5, the surface precipitation reaction dominated, and both Al(III) and Si(IV) formed a new oxide film in the original surface, protecting against dissolution of SiO 2(s) by OH −.