Removal Rate Research Articles

Incidence, risk factors and endoscopic retrieval of proximally migrated pancreatic stents: 25 years of experience in a high-volume center - a case controlled study.

Proximal migration is one of the complications after pancreatic stenting. This study aims to determine the incidence, risk factors and endoscopic treatment of proximally migrated pancreatic stents. A retrospective search of all the endoscopic retrograde cholangiopancreatography (ERCP) records was conducted from 1997 to 2022 in our tertiary center. Proximal migration of the pancreatic stent was defined as when the stent shifted completely into the pancreatic duct and the distal end of the stent was no longer visible at the duodenal papilla. A total of 9017 pancreatic duct stentings of 6083 patients were performed. The proximal migration rate was 0.2% (17/9017). Three predictive factors for proximal migration were identified: pancreatic duct stones (OR, 0.107), residual pancreatic duct stones (OR, 8.290) and straight-shape stent (OR, 4.725). After including 19 patients transferred from other hospitals, 46 ERCPs were performed to retrieve the proximally migrated stents in 36 patients. The success rate of endoscopic removal was 80.6% (29/36). 1 (2.8%) patient was referred to surgery, and 6 patients had new pancreatic stents placed for conservative treatment. 21.7% (10/46) cases developed post-ERCP pancreatitis and 2.2% (1/46) developed infection. Proximal migration of pancreatic stents is less common, but deserves more attention. Endoscopy is efficient in retrieving proximally migrated stents. In patients with residual pancreatic duct stones and straight stent, the risk of proximal migration is significantly increased.

Chronic nitrogen legacy in the aquifers of China

About half of the global drinking water comes from groundwater, yet groundwater quality is threatened by high nitrate concentrations globally. Our understanding of groundwater nitrate concentrations is often limited by inaccessibility of groundwater and scarcity of nitrate data in groundwater. Here we used machine learning and decision tree-heatmap analysis by compiling nitrate concentrations and isotope data from 4047 groundwater sites across China to understand their dynamics and drivers across gradients of geographical, climate, and human factors. Results show that nitrate concentrations vary substantially over depth and are generally lower in deeper groundwater, indicating potentially higher nitrate removal rates according to nitrate isotopic pattern such as denitrification at depth. At similar groundwater aquifer depths, nitrate concentrations are highest in urban regions with high population density. In addition, nitrate concentrations are generally higher in arid northern China than humid southern China. Interestingly, while groundwater nitrate concentrations are lower at deeper depths, slow groundwater flow also indicates prolonged nitrogen legacy. Although there has been an overall decline in groundwater nitrogen pollution in China since 2016, persistent pollution has lingered. Future strategies for groundwater quality protection in China should address the long-term legacy of nitrate in different aquifers and rising nitrogen levels in groundwater.

Microbial community structure and functional characteristics in a membrane bioreactor used for real rural wastewater treatment.

Membrane bioreactors (MBRs) have been widely used in the field of wastewater treatment because of their small footprint and high treatment efficiency. In this research, 10 rural wastewater treatment sites in China that employ the MBR process were systematically studied. Specifically, treatment of actual domestic wastewater using MBRs was examined by high-throughput 16S rRNA gene sequencing to explore the microbial community composition and perform function prediction. The data of water quality parameters revealed high removal rates of chemical oxygen demand and NH4+-N in all the sites. Proteobacteria were absolutely dominant in all the sites. Thauera, Nitrospira, Ferribacterium, and Dechloromonas were the main functional genera responsible for nitrogen and phosphorus removal at the tested sites. Nitrospira includes conventional nitrite-oxidizing bacteria and complete ammonia-oxidizing bacteria. Among them, 26 genes related to nitrogen metabolism were retrieved according to gene prediction, which verified the good NH4+-N removal efficiency at the tested sites. This study focuses on the analysis of microbial community structure and functional characteristics of MBR-based treatment systems for rural wastewater treatment, thereby providing a microbial basis for improving rural wastewater treatment processes.

Inoculum selection and hydraulic retention time impacts in a microbial fuel cell treating saline wastewater

Microbial fuel cell (MFC) technology has received increased interest as a suitable approach for treating wastewater while producing electricity. However, there remains a lack of studies investigating the impact of inoculum type and hydraulic retention time (HRT) on the efficiency of MFCs in treating industrial saline wastewater. The effect of three different inocula (activated sludge from a fish-canning industry and two domestic wastewater treatment plants, WWTPs) on electrochemical and physicochemical parameters and the anodic microbiome of a two-chambered continuous-flow MFC was studied. For each inoculum, three different HRTs were tested (1 day, 3 days, and 6 days). The inoculum from the fish canning industry significantly increased voltage production (with a maximum value of 802 mV), power density (with a maximum value of 78 mW m−2), coulombic efficiency (with a maximum value of 19.3%), and organic removal rate (ORR) compared to the inocula from domestic WWTPs. This effect was linked to greater absolute and relative abundances of electroactive microorganisms (e.g., Geobacter, Desulfovibrio, and Rhodobacter) and predicted electron transfer genes in the anode microbiome likely due to better adaption to salinity conditions. The ORR and current production were also enhanced at shorter HRTs (1 day vs. 3 and 6 days) across all inocula. This effect was related to a greater abundance and diversity of bacterial communities at HRT of 1 day compared to longer HRTs. Our findings have important bioengineering implications and can help improve the performance of MFCs treating saline effluents such as those from the seafood industry.Key points• Inoculum type and HRT impact organic matter removal and current production.• Changes in bioenergy generation were linked to the electroactive anodic microbiome.• Shorter HRT favored increases in the performance of the MFC.Graphical

Development and Efficiency Evaluation of Microplastic Removal Filter for Laundry Machines

Microplastics contained in laundry wastewater are identified as the main cause of marine microplastics, accounting for approximately 35% of marine microplastics. In this study, a four-stage microplastic filter for laundry wastewater was developed and the removal rates of microplastics, COD, SS, and turbidity were checked through 50 tests to confirm the efficiency of the filter. The microplastic removal rate was confirmed using μFTIR with a high efficiency of 98.5% on average for 50 tests. The microplastics contained in laundry wastewater were identified as 57% PE, 9% PET, 9% PA, 8% PU, 8% PP, 6% PPMA, and 3% PAN. COD was measured using the COD manganese method, and the COD removal rate of the laundry wastewater filter was an average of 92% for 50 times. SS was verified by filtration using a vacuum pump and the average removal rate was 80% during 50 tests. Turbidity was confirmed with an average removal rate of 88% using a turbidity meter. As a result of the experiment, it was confirmed that when the developed filter was installed in laundry wastewater, not only microplastics but also various water pollutants were reduced. In addition, the water quality pollution index showing the highest correlation with microplastics in laundry wastewater was SS, and the p-value was confirmed to be 0.000.

Construction of Sub-nano Channels ofAmino Pillar[6]arene Inspired Biomimetic Porous Roots for Specific Removeof Imazamox.

The root ducts play an important role in the plant's transport of nutrients from the soil. Based on the selective transport characteristics of plant roots, amino pillar[6]arene bionic porous root sub-nano channelmembrane wereconstructed toremove Imazamox. Imazamox (IM) is an effective imidazolinone herbicide frequently utilized in soybean fields to control a wide range of annual grasses and broad-leaved weeds.However, it is important to note that while IM is effective in controlling the growth of weeds, its residues can affect the plants that are later planted.Developing a material that can efficiently and selectively remove IM from the environment poses a significant challenge in the realm of agricultural residue removal.Alayer-upon-layer covalent assembly was formedthrough the reaction of amino pillar[6]arene with terephthalaldehyde using an aldehyde-amine Schiff-base reaction.The cavity of amino pillar[6]arenal is used to realize the host-guest interaction of IM. This enabled the development of a membrane with high selectivity for the extraction and removal of IM. The removal rate is 4.66-21.91 times higher than that of other pesticide chemicals. The successful development of the highly selective porous root bionic membrane provides a broad prospect for its application and development in agricultural production.

Sustainability metrics targeted optimization and electric discharge process modelling by neural networks

Aluminium and its alloys, especially Al6061, have gathered significant interest among researchers due to its less density, great durability, and high strength. Due to their lightweight properties, the precise machining of these alloys can become expensive through conventional machining operations for intricate products. Therefore, non-traditional machining such as electric discharge machining (EDM) can potentially be opted for the cutting of Al6061. EDM is often criticized due to its low machining rates, therefore, in the current work, cryogenic treatment (CT) has been performed on the brass electrode to evaluate the improvement in the machining rates. In addition, kerosene oil (KO) has been engaged in traditional EDM which is replaced with the deionized water (DI) based dielectric as a sustainable alternative. The machining variables such as spark voltage (SV), pulse-on-time (PON), peak current (IP), and Al2O3 powder concentration (CP) have been chosen to determine the material removal rate (MRR), surface roughness (SR), and specific energy consumption (SEC) while comparing non-treated (NT), and cryogenically treated (CT) brass electrodes during EDM. The results were analyzed through optical micrographs, scanning electron microscopy (SEM) analysis, energy dispersive x-ray (EDX) examination, and 3D surface plots. An artificial neural network (ANN) has been constructed for the better prediction of output responses. Moreover, multi-response optimization through the non-dominated sorting genetic algorithm (NSGA-II) has also been performed. The magnitudes of MRRCT, SRCT, and SECCT obtained by multi-response optimization are 64.82%, 27.45%, and 46.60% are better than the values obtained by un-optimized settings of CT brass electrodes. However, the optimal magnitudes of processing parameters are IP = 24.85 A, SV = 2.18 V, PON = 119.11 µs, and CP = 1.05 g/100 ml.

Treatment Performance and Characteristics of Biofilm Carriers in an Aerobic Waterwheel-Driven Rotating Biological Contactor

Rotating biological contactors (RBCs) are widely utilized in aerobic wastewater treatment due to their high stability, efficiency, and ease of maintenance. The choice of disc carrier material for biofilm formation is a critical factor influencing treatment performance. In the context of rural domestic wastewater treatment, the biofilm carriers must balance cost-effectiveness and high efficiency. This study focuses on the aerobic unit of a combined anoxic denitrification–deodorization filter–aerobic RBC system, specifically, the waterwheel-driven aerobic RBC, and evaluates three types of biofilm carrier media: felt, carbon felt, and nonwoven fabric. The study compares their pollutant removal performance and biofilm enrichment characteristics to identify the optimal material. The results indicate that RBCs using nonwoven fabric as the biofilm carrier exhibit superior nitrification efficiency and biocompatibility compared to the other materials, achieving average removal rates of 84.3% for CODCr and 80.5% for ammonia nitrogen. While the addition of nonwoven fabric slightly reduced the driving efficiency of the waterwheel-driven aerobic RBC, it significantly enhanced oxygen transfer efficiency, which explained the enhanced organic degradation and ammonia nitrification. During the biofilm stable phase, the two-stage waterwheel-driven RBC with a nonwoven fabric carrier achieved average CODCr and ammonia nitrogen removal rates of 86.76 ± 0.85% and 92.15 ± 1.49%, respectively. Nonwoven fabric demonstrates significant potential as a biofilm carrier for aerobic rotating biological contactors.

Application of DynaCT biliary soft tissue reconstruction technology in diagnosis and treatment of hepatolithiasis.

Hepatobiliary stone disease involves an intrahepatic bile duct stone that occurs above the confluence of the right and left hepatic ducts. One-step percutaneous transhepatic cholangioscopic lithotripsy (PTCSL) using the percutaneous transhepatic one-step biliary fistulation (PTOBF) technique enables the clearing of intrahepatic stones and the resolution of strictures. However, hepatolithiasis with associated strictures still has high residual and recurrence rates after one-step PTCSL. DynaCT can achieve synchronized acquisition with a flat-panel detector during C-arm rotation. The technical approach and application value of DynaCT biliary soft tissue reconstruction technology for the diagnosis and treatment of hepatolithiasis with bile duct stenosis were evaluated in this study. To explore the value of DynaCT biliary soft tissue reconstruction technology for the diagnosis and treatment of hepatolithiasis with bile duct stenosis, and to assess the feasibility and effectiveness of the PTOBF technique guided by DynaCT biliary soft tissue reconstruction technology. The clinical data of 140 patients with complex biliary stenosis disease combined with bile duct stenosis who received PTOBF and were admitted to the First Affiliated Hospital of Guangzhou Medical University from January 2020 to December 2024 were collected. The patients were divided into two groups: DynaCT-PTOBF group (70 patients) and conventional PTOBF group (70 patients). These groups were compared in terms of the preoperative bile duct stenosis, location of the liver segment where the stone was located, intraoperative operative time, immediate stone retrieval rate, successful stenosis dilatation rate, postoperative complication rate, postoperative reoperation rate, stone recurrence rate, and stenosis recurrence rate. DynaCT biliary soft tissue reconstruction technology was successfully performed in 70 patients. The DynaCT-PTOBF group had a higher detection rate of target bile ducts where bile duct stones and biliary strictures were located than the PTOBF group. Compared with the PTOBF group, the DynaCT-PTOBF group was characterized by a significantly greater immediate stone removal rate (68.6% vs 50.0%, P = 0.025), greater immediate stenosis dilatation success rate (72.9% vs 55.7%, P = 0.034), greater final stenosis release rate (91.4% vs 75.7%, P = 0.012), shorter duration of intraoperative hemorrhage (3.14 ± 2.00 vs 26.5 ± 52.1, P = 0.039), and lower incidence of distant cholangitis (2.9% vs 11.4%, P = 0.49). There were no significant differences between the two groups in terms of the final stone removal rate, reoperation rate, or long-term complication incidence rate. DynaCT biliary soft tissue reconstruction technology guiding the PTOBF technique in patients with hepatolithiasis with bile duct stenosis is feasible and accurate. It may be beneficial for optimizing the preoperative evaluation of the PTOBF technique.

Decline in Water Treatment Efficiency of an Estuarine Constructed Wetland over Its Operating Years

Estuarine constructed wetlands (ECWs) play a role as ecological barriers in the control of external pollution in lakes. Usually, ECWs show reduced water treatment efficiency after many years of operation compared to their initial performance. However, it is unclear how the water purification efficiency of an ECW changes over time. After over a decade of tracking analysis on an ECW, this study found that it indeed played a significant role in achieving water quality improvement effects. The average removal rates for total nitrogen (TN) and total phosphorus (TP) and the permanganate index (CODMn) were 36.2%, 26.7%, and 30.7%, respectively, with annual reductions of 1.6 t/a, 20.8 t/a, and 44.6 t/a. The surface hydraulic load is a critical indicator for the design and operational management of ECWs. The reduction loads of TP, TN, and CODMn increased with the rise in surface hydraulic load, indicating that this ECW project had certain advantages in treating large-volume water bodies. However, when strict CODMn treatment is needed, the surface hydraulic load should be reduced. During the high-efficiency period (2010–2015), the treatment effects on TN and TP were more than twice those during the degradation period (2016–2021), and the effect on CODMn was about 1.5 times greater. With increased operation years, the TN removal rate declined most rapidly due to pollutant accumulation and sediment release.

NaOH-Enhanced Wet Air Oxidation of Municipal Sludge for High-Quality Carbon Source Production

Many volatile fatty acids (VFAs) are produced after wet air oxidation, which could be a potential carbon source. In this study, we investigated the impact of NaOH on the removal of hazardous organics and the changes in the produced carbon source. The total and soluble chemical oxygen demand (SCOD) removal rates decreased to 47.9% and 55.3% with 51.6% NaOH addition. The removal rates of total suspended solids (82–85%) and volatile suspended solids (97–99%) remained stable under all conditions. Additionally, the concentrations of acetic acid and isovaleric acid increased with a high pH value. Fluorescent substances closely related to aromatic protein and fulvic acid-like substances were identified and degraded significantly with the addition of NaOH. Moreover, 41.3% NaOH addition (initial pH 13.0) could yield a VFAs/SCOD ratio of 30.5%, demonstrating the good biocompatibility of the carbon source. The effect of the nitrogen element was also considered, with the ratio of the 5-day biological oxygen demand to the total nitrogen being 7.2, indicating that the oxidation solution could provide an abundant carbon source. Thus, the sludge-derived carbon source is suitable to supply biological treatment units for municipal wastewater.

Experimental Study on Efficient Short Electric Arc Turning of Titanium Alloy

This study investigates a novel short electric arc vertical turning method for machining titanium alloy shafts. The method was successfully applied to titanium alloy rods, and its effects on material removal rate (MRR), surface roughness, roundness, and cross-sectional morphology were analyzed at varying processing voltages. The results indicate that the MRR and surface quality improve with increased voltage, reaching a maximum of 231 mm3/min and 26 μm surface roughness at 32 V. However, surface roughness deteriorates with higher duty cycles and voltages due to unstable discharges. Roundness deviations are minimized with higher rotational speeds, which enhance uniform material removal and arc stability. Metallographic analysis revealed an increased heat-affected zone and recast layer thickness at higher voltages. This method demonstrates high machining efficiency and improved surface quality, making it suitable for titanium alloy shaft manufacturing in advanced engineering applications.

Achieving Near Infrared Photodegradation by the Synergistic Effect of Z-Scheme Heterojunction and Antenna of Rare Earth Single Atoms.

Near-infrared light response catalysts have received great attention in renewable solar energy conversion, energy production, and environmental purification. Here, near-infrared photodegradation is successfully achieved in rare earth single atom anchored NaYF4@g-C3N4 heterojunctions by the synergistic effect of Z-scheme heterojunction and antenna of rare earth single atoms. The UV-vis light emitted by Tm3+ can not only be directly absorbed by g-C3N4 to generate electron-hole pairs, realizing efficient energy transfer, but also be absorbed by NaYF4 substrate, and generating photo-generated electrons at its impurity level, transferring the active charge to the valence band of g-C3N4, forming a Z-scheme heterojunction and further improving the photocatalytic efficiency. Importantly, Tm single atoms has multiple functions such as acting as charge transfer channels to facilitate charge transfer, regulating the critical distance of energy transfer, and prolonging electron-hole pair lifetime. Under NIR light, it exhibited remarkable performance in degrading antibiotics (the removal rate of TC reached 91% for 6 h) while maintaining excellent stability. The LC-MS/MS technology is used to reveal the reaction intermediates, active species, and reaction pathways, and the complex mechanism of photodegradation is further proposed. This study provides experimental and theoretical support for designing and synthesizing catalysts with near-infrared light response characteristics.

Nitrogen/Sulfur Co-Doped Biochar for Peroxymonosulfate Activation in Paracetamol Degradation: Mechanism Insight and Toxicity Evaluation

Advanced oxidation processes based on either peroxydisulfate (PDS) or peroxymonosulfate (PMS), collectively termed persulfate-based advanced oxidation processes (PS-AOPs), show potential in wastewater treatment applications. In this work, the nitrogen (N) and sulfur (S) co-doped biochar (NSBC) was prepared via a one-step pyrolysis of coffee grounds at 400 to 800 °C as a PMS activator for degrading paracetamol (PCT). The non-metallic NSBC demonstrated exceptional catalytic activity in activating PMS. In the NSBC-800/PMS system, 100% of PCT was completely degraded within 20 min, with a high reaction rate constant (kobs) of 0.2412 min−1. The system’s versatility was highlighted by its degradation potential across a wide pH range (3–11) and in the presence of various background ions and humic acids. The results of various experiments and characterization techniques showed that the system relied on an NSBC-800-mediated electron transfer as the main mechanism for PCT degradation. Additionally, there was a minor involvement of 1O2 in a non-radical degradation pathway. The graphitic N and thiophene-S (C-S-C) moieties introduced by N/S co-doping, as well as the carbonyl (C=O) groups of the biochar, were considered active sites promoting 1O2 generation. The total organic carbon (TOC) removal rate reached 37% in 120 min, while the assessment of the toxicity of the degradation products also affirmed the system’s environmental safety. This research provides a novel method for preparing environmentally friendly and cost-effective carbon-based catalysts for environmental remediation.

Multi-Channel Electrical Discharge Machining of Ti-6Al-4V Enabled by Semiconductor Potential Differences

Titanium alloys are difficult to machine using conventional metal cutting methods due to their low thermal conductivity and high chemical reactivity. This study explores the new multi-channel discharge machining of Ti-6Al-4V using silicon electrodes, leveraging their internal resistivity to generate potential differences for multi-channel discharges. To investigate the underlying machining mechanism, the equivalent circuit model was developed and a theoretical simulation was carried out. Comparative experiments with silicon and conventional copper electrodes under identical parameters were also conducted to analyze discharge waveforms, material removal rate, surface quality, and heat-affected zones (HAZ). The results demonstrate that the bulk resistance of silicon is the main mechanism for generating multi-channel discharges. This process efficiently disperses the discharge energy of the single discharge pulse, resulting in smaller craters, smoother machined surfaces, and shallower recast layers and HAZ.

Research on quantitative characterization methods for two-dimensional cleanliness and three-dimensional removal rate of aircraft skin laser paint removal

The quantitative assessment of aircraft skin paint removal can more objectively reflect the efficacy of laser paint stripping. Post-laser paint removal, a comprehensive evaluation was conducted through both two-dimensional image analysis and three-dimensional profile analysis. This yielded two-dimensional cleanliness parameters based on the coverage of residual paint and three-dimensional removal efficiency metrics based on the volume of the stripped coating. The findings revealed that the two-dimensional cleanliness levels achieved by laser paint removal at varying degrees were recorded as 21.17%, 45.02%, 57.35%, 79.16%, and 97.79% respectively. Correspondingly, the three-dimensional removal rates were quantified at 85.94%, 87.97%, 89.12%, 94.84%, and 99.52% respectively. This research successfully provides an intuitive and quantitative characterization of both the two-dimensional cleanliness and three-dimensional removal rate in laser paint stripping, offering valuable references and a solid foundation for the objective and practical evaluation of laser paint removal effectiveness.

Synergistic Removal of Rare Earth Elements from Radioactive Molten Salt via Electrodeposition and Adsorption.

Recycling waste salt in the dry reprocessing of nuclear fuel and reducing electric energy consumption in the electrorefining process are crucial steps toward addressing significant challenges in this field. The present study proposes a novel approach to purify waste salt by selectively adsorbing excessive fission products using 5A molecular sieves (5A), based on the principles of electrorefining, with the ultimate aim of achieving sustainable development in nuclear fuel. First, Lutetium (Lu)-Bi alloy was synthesized through constant potential electrolysis in the LiCl-KCl-LuCl3 melt, resulting in a 90.59% extraction rate of Lu(III) on the Bi electrode. Subsequently, following the electrolysis process, the waste salt underwent high-temperature adsorption with a 5A for purification. The results of the experiment indicate that the utilization of 5A for adsorption can lead to a remarkable removal efficiency of Lu, reaching an impressive rate of 99.70%. Consequently, when combined with electrolytic reduction, the overall extraction rate of Lu is significantly enhanced to a remarkable 99.98%. Finally, experiments on the coexistence of rare earth elements were conducted, revealing a significant removal rate for Y, Ho, Tm, Yb, and Lu. This study presents innovative solutions for effectively utilizing waste salt in the nuclear fuel cycle.

Hybrid approach for parametric optimization of wire-electrochemical spark micromachining of borosilicate glass

This work intends to implement a hybrid strategy for the multiobjective optimization of a wire-electrochemical spark micromachining (WECSMM) process, integrating the Taguchi technique and response surface approach. Initially, the optimum level of process variables, such as, thickness of workpiece, feed velocity of wire, concentration of electrolyte, and applied voltage, are evaluated using the characteristic loss function of Taguchi. After the process variables are optimized, the response surface model is built and refined using the central values that represent the best values. An experimental plan for borosilicate glass slicing was carried out during WECSMM, utilizing the L9 Taguchi design process. For simultaneous optimization, the two attribute criteria like surface roughness ( Ra) and material removal rate (MRR) have been chosen. When comparing the outcomes of a single strategy with the hybrid approach, the results demonstrate a significant increase in both quality aspects. As contrasted to Taguchi Methodology (TM), the couple approach was shown to increase MRR by 192% and lower Ra by 10%, respectively.

Efficiency of Nitrate Removal from Groundwater by Adsorption on Raw and Treated Bentonite

The objective of this study was to treat groundwaters with a high initial nitrate (NO3−) content (125 mg/L, and 177 mg/L) by adsorption onto a local bentonite in its raw state (RB), treated with a ratio of H2SO4/bentonite = 0.2 (B0.2), and another treated with a ratio of H2SO4/bentonite = 0.6 (B0.6). Non-linear modelling of the nitrate adsorption kinetics of two water samples showed the pseudo-first-order model was the best fit, confirming that nitrate retention on each adsorbent was due to chemisorption. The intra-particle diffusion curves were multi-linear, indicating that there are other mechanisms influencing nitrate ion adsorption on bentonite than intra-particle diffusion. The effectiveness of the adsorbents tested was in the following order: B0.6 > B0.2 > RB. This finding demonstrates that acid activation of the clay improves its characteristics. The optimal adsorbent dose was found to be 1 g/L after changing the bentonite dose from 0.1 to 4 g/L. The pH of the treatment affects nitrate removal rates. The greatest results are achieved at pH levels close to 6. It also appears that the treatment was more effective for water with low initial nitrate levels.

Strong Chelating Agent Accelerated High Performance on Copper Polishing

Abstract Sustainability in Cu chemical mechanical polishing (CMP) processing for highly integrated device manufacturing demands electric energy saving and slurry consumption reduction, which can be achieved through faster CMP. A strong chelating agent, quinaldic acid (QA), was chosen to accelerate the polishing rate on Cu in an acidic H2O2-BTA system. The strong complexing capability of QA with Cu ions can facilitate the formation of a porous and loose copper oxide film on the Cu surface in acidic H2O2 solution and soften the microhardness of the Cu surface, which is beneficial for fast Cu removal in CMP process. The chemistry of QA with Cu in acidic solution was studied by electrochemical methods and physical measurements. The optimized QA containing polishing slurry produced a high Cu removal rate about 1.8 um/min with a good flatness.