Alkaline Cleaning Solution Research Articles

Hyperbranched polymer wrapped UIO-66-NH2 as covalent intermediate layer to enhance polyamide membrane for Li+/Mg2+ separation and acid/alkaline stability

Herein, hyperbranched polyamide covalently wrapped UIO-66-NH2 nanoparticles (PA-UIO-66-NH2) were designed and synthesized via the in-situ self-condensation polymerization of 3,5-diaminobenzoic acid. Mixed matrix intermediate layer thus was prepared by doping it into the diazotization-coupling reaction, to tune the pore size and hydrophilic of the polysulfone (PSF) support. The interfacial polymerized polyamide (PA) nanofilm formed on modified PSF support exhibited optimized improved size exclusion and Donnan effect on separation of Li+/Mg2+. Experimental data showed that the Li+/Mg2+ separation factor (32.24 at Mg2+/Li+ ratio of 15.3) of the PA/m-PSF-2 membrane tuned with such intermediate layer reached 13.27 times that of the controlled PA/PSF-0, and surpassed some commercial PA (NF 270, DL, and DK) and literature reported membranes. Moreover, the related LiCl/water flux enhanced from 1.39 to 1.88 times compared with that of the PA/PSF-0 membrane, up to 244.25 kg m−2 h−1. Such mixed matrix intermediate layer can adsorb and isolate acidic or alkaline cleaning solutions, significantly reducing the impact of cleaning solutions on the rejection rate and water flux of the PA nanofilm during actual application. This work demonstrated that the mixed matrix covalent intermediate layer was an effective approach to construct the fine-tuned structural and robust PA nanofiltration (NF) composite membrane.

Direct Membrane Filtration (DMF) of municipal wastewater – A study on the prevention and remediation of fouling

Direct membrane filtration (DMF) has gained a lot of attention in recent years because of its potential to treat low-strength and low temperature wastewater, where biological based treatments are inefficient. However, fouling is a major concern which keeps this technique from being more widely used. The main aim of this study was to investigate membrane fouling, its mitigation approaches and the organic/nutrient retention during DMF of municipal wastewater by adjusting operational parameters and pretreating the sewage. In a laboratory-scale setup employing crossflow to mitigate fouling, both ultrafiltration and microfiltration membranes were utilized. Physicochemical pre-treatment of sewage with polyaluminum chloride and polyamide significantly inhibited membrane fouling and improved organics/nutrient retention. Subsequent experiments with physiochemically pre-treated sewage, using microfiltration and ultrafiltration separately, revealed that (i) an increase in crossflow velocity from 1 to 2 m s −1 improved filtration performance by reducing irreversible fouling, (ii) elevating transmembrane pressure from 0.18 to 0.4 bar increased both reversible and irreversible fouling, and (iii) periodic relaxation increased the extent of irreversible fouling, contributing to higher overall fouling in ultrafiltration. When employing DMF for sewage concentration, ultrafiltration demonstrated superior filtration performance and organics retention compared to microfiltration. Furthermore, through pre-precipitation and microsieving (100 μm) followed by DMF with ultrafiltration membranes, a remarkable removal efficiency of 92 % for chemical oxygen demand (COD), 98 % for total phosphorus (TP), and 100 % for total suspended solids (TSS) was achieved. By cleaning the fouled membranes using an alkaline cleaning solution (Ultrasil-10) at 50 °C, combined with a crossflow of 1 m s−1, the permeability was completely restored. Overall, this study demonstrates that by optimizing operational settings and cleaning conditions, a sustainable DMF process for wastewater treatment with controlled membrane fouling and improved resource recovery can potentially be developed for upscaling. Short abstractThis study investigated the effectiveness of direct membrane filtration for municipal wastewater treatment. It was found that physicochemical pre-treatment with polyaluminum chloride and polyamide significantly reduced membrane fouling and improved nutrient retention. Ultrafiltration membranes demonstrated superior performance and nutrient retention compared to microfiltration membranes. By optimizing operational parameters and cleaning conditions, a sustainable direct membrane filtration process with controlled fouling and improved resource recovery can be developed for wastewater treatment.

Research on the removal efficiency and membrane fouling analysis of nanofiltration membranes under the combined pollution of emerging contaminants

Based on the research background of five emerging contaminants (ECs)— sulfadiazine (SD), sulfamethoxazole (SMZ), malathion, hexachlorobenzene (HCB), and bisphenol A (BPA)—which can be detected in trace amounts in a river basin in southern China, a spiking experiment was conducted to effectively address the potential impact risks of these contaminants. The experiment aimed to investigate the removal efficiency and membrane fouling of nanofiltration membranes (NF) under the combined pollution of these ECs. The experimental results show that under the combined pollution of these ECs, the NF exhibits good removal efficiency for all five ECs, with removal rates of approximately 83 ± 2 %, 84 ± 3 %, 76 ± 3 %, 73 ± 6 %, and 80 ± 5 % for SD, SMZ, malathion, HCB, and BPA, respectively. Additionally, NF also has high efficiency in removing other pollutants, with removal rates for chromaticity, CODMn, and total hardness at 80 ± 2 %, 60 ± 3 %, and 62 ± 2 %, respectively, and over 80 % of fluorescent substances were removed. Analysis of the key operating indicators of the NF under the combined pollution of ECs revealed that the membrane flux decreased slightly faster compared to without the combined pollution of ECs, and both the membrane fouling index and membrane resistance increased to a certain extent. Furthermore, the analysis of the NF chemical cleaning solutions showed that these ECs can be detected in both alkaline and acid cleaning solutions. Analysis of membrane dissection on NF revealed that severe cake layer contamination formed on the membrane surface both under and without the combined pollution of ECs, the presence of ECs is worse than the absence of ECs.

Enhanced particle removal ability of two representative nonionic surfactants: A reasonable interpretation based on DFT and coarse-grained molecular dynamics methods

Cleaning of copper surfaces after chemical mechanical polishing is indispensable for removing particle residues, which is a critical step in integrated circuits manufacturing. This paper introduces two nonionic surfactants, coconut oil diethanolamine (CDEA) and fatty alcohol polyoxyethylene ether (AEO-9), into a basic alkaline cleaning solution comprising tetraethyl ammonium hydroxide and lysine to investigate their abilities to enhance particle removal performance. Cleaning performance was measured with scanning electron microscopy, which showed that the two surfactants achieved excellent particle removal efficiency (above 95 %), with CDEA performing slightly better in all tested concentrations. Concerning critical micelle concentration, surface tension tests showed that CDEA (at 1500 ppm) had superior wettability and dispersive capacity compared with AEO-9 (at 2000 ppm) and could prevent particle redeposition more effectively. Using density functional theory, CDEA was found to have more polar groups to form hydrogen bonds with the hydrophilic surface of colloidal silica particles or bond with the copper substrate, explaining CDEA’s ability to lower the surface tension of the cleaning solution and improve the zeta potential between particles and the copper substrate. Finally, based on the Martini forcefield, simulations of coarse-grained molecular dynamics provided valuable theoretical insights into the different dispersion abilities of the two nonionic surfactants that CDEA had a more significant diffusion coefficient (0.073 Å2/ps) and was able to form micelles more efficiently in solution compared with that of AEO-9 (0.066 Å2/ps).

Alleviation of RO membrane fouling in wastewater reclamation plants using an enhanced acid-base chemical cleaning method

Membrane fouling has always been a critical constraint in the operation of the reverse osmosis (RO) process, and chemical cleaning is essential for mitigating membrane fouling and ensuring smooth operation of the membrane system. This paper presents an optimized chemical cleaning method for the efficient cleaning of RO membranes in full-scale applications. Compared to the regular cleaning method (cleaning with 0.1 % NaOH + 1 % ethylenediaminetetraacetic acid + 0.025 % sodium dodecyl benzene sulfonate followed by 0.2 % HCl), the optimized cleaning method improves the cleaning efficiency by adding sodium chloride to the alkaline cleaning solution and citric acid to the acid cleaning solution. Notably, the membrane flux recovery rate with the optimized cleaning method is 45.74 %, and it improves the cleaning efficiency by 1.65 times compared to the regular cleaning method. Additionally, the optimized cleaning method removes 30.46 % of total foulants (organic and inorganic), which is 2.11 times higher than the regular cleaning method. The removal of inorganic ions such as Fe, Ca, and Mg is significantly improved with the optimized cleaning method. For organic matter removal, the optimized cleaning method effectively removes more polysaccharides, proteins, and microbial metabolites by disrupting the complex structures of organic matter. Furthermore, it also changes the microbial community structure on the RO membrane surface by eliminating microorganisms that cannot withstand strong acids, bases, and high salt environments. However, Mycobacterium can adapt to these harsh conditions, showing a relative abundance of up to 84.13 % after cleaning. Overall, our results provide a new chemical cleaning method for RO membranes in full-scale applications. This method effectively removes membrane foulants and enhances the understanding of the removal characteristics of foulants on RO membrane surfaces by chemical cleaning.

The Resistance of Polyethersulfone Membranes on the Alkaline Cleaning Solutions.

Polyethersulfone (PES) is a polymer popularly used to produce ultrafiltration (UF) membranes. PES is relatively hydrophobic; thus, hydrophilic ingredients are added to the membrane matrix to reduce the fouling intensity. Ingredients such as polyvinylpyrrolidone (PVP) reduce the resistance of PES to NaOH solutions. This study investigated the possibility of using PES membranes for the separation of alkaline cleaning solutions. For this purpose, self-made PES membranes and commercial ultrafiltration PES membranes (UE10-10 kDa and UE50-100 kDa) containing PVP additive were used. The membranes were soaked for 18 months in alkaline (pH = 11.3-11.5) solutions of car washing fluids. It has been found that long-term contact with these solutions caused changes in the structure of the surface layer, especially of membranes containing PVP. As a result, the separation of dextran (100-200 kDa) decreased by 30-40% for PES membranes, 30-40% for UE10 and 40-60% for UE50. Despite these changes, the separation efficiency (rejection of COD, NTU and anionic surfactants) of synthetic car wash wastewater (mixture of surfactants and hydrowax) was similar to the results obtained for pristine membranes.

Synergistic Effect of Composite Complex Agent on BTA Removal in Post-Cu-CMP: Experimental and Theoretical Analysis

Nowadays the development of nanoscale-interconnected integrated circuit chips makes the chemical mechanical polishing (CMP) and post-CMP cleaning more challenging. In general, organic residues such as benzotriazole (BTA) can adsorb on the wafer surface after CMP process and form thin films to prevent the contact between cleaning solution and the wafer surface, which thus can seriously affect the post-CMP cleaning process. And the efficient removal of BTA remains problematic due to the potential introduction of additional impurities. Therefore, a new alkaline cleaning solution based on citric acid (CA) was proposed to improve the removal efficiency of BTA. Results exhibit that the cleaning efficiency of BTA residues can reach 98.86% with 400 ppm tetraethyl ammonium hydroxide (TEAH) and 0.6 wt% CA (pH = 10.5). X-ray photoelectron spectroscopy (XPS) measurements show that the cleaning solution can coordinate with copper ions to break the ionization balance of Cu-BTA. In addition, the electronic properties and reaction sites on copper surface were determined by quantum chemical calculation and density functional theory (DFT). The theoretical analysis indicates that CA has hydroxyl and carboxyl functional groups, and its presence with TEAH can promote the complexation of Cu ions, which accelerates the breakage of Cu-BTA and the desorption of BTA from the copper surface.

Synergistic Effect of Complexing Agent TAD and Corrosion Inhibitor PZ on BTA Removal in Copper Post-CMP Cleaning

Benzotriazole (BTA) as a common corrosion inhibitor in the chemical mechanical polishing (CMP) process, can effectively protect the copper (Cu) surface, but its organic residues will form a passivation film on the wafer surface to prevent the contact between the cleaning solution and the wafer surface, so the removal of BTA is a major problem in the post-CMP cleaning. In this paper, N,N’-Bis(3-aminopropyl)−1,2-ethanediamine (TAD) and pyrazole (PZ) were used as the main components in the alkaline cleaning solution and fatty alcohol polyoxy ethylene ether (JFCE) was added as an auxiliary surfactant to investigate the removal of BTA. The complexation ability of TAD and the corrosion inhibition ability of PZ were verified by electrochemical experiments, and the reaction sites of the interaction between TAD and Cu surface were analyzed by quantum chemical calculations. Meanwhile, the mechanism of the synergistic removal of BTA by TAD and PZ was investigated by electrochemical methods. The final optimized cleaning solution consisted of 1 mmol L−1 TAD, 0.1 mmol L−1 PZ and 1 wt% JFCE and its good cleaning performance was verified by contact angle measurements, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), which provided guidance for the development of the cleaning solution.

Application of an optimized alkaline cleaning solution for inhibitor removal during the post-CMP process: Performance evaluation and mechanism analysis

With the continuous miniaturization of the feature size of semiconductor integrated circuits, the development of chemical mechanical polishing (CMP) technology for copper interconnection has been promoted, and at the same time, more stringent requirements and challenges have been put forward for post-CMP cleaning technology. Benzotriazole (BTA), which has been used as an inhibitor to decrease metal corrosion especially in copper CMP process, is the main object to be removed after the CMP process due to its highly hydrophobic nature. However, the current post-CMP cleaning method cannot achieve an effective balance between high removal efficiency of BTA and excellent surface quality after CMP cleaning. Therefore, a novel and efficient alkaline cleaning solution for post-CMP cleaning of copper is proposed, which is based on tetraethylammonium hydroxide (TEAOH), l-glutamate (Glu) and polyvinylpyrrolidone (PVP). The cleaning effect of copper surface was characterized by contact angle measurement, electrochemical system, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The ion exchange of TEAOH and Glu promotes desorption of BTA molecules from the copper surface. The presence of PVP plays a key role in improving the surface quality after cleaning. This cleaning solution was proved to be effective for BTA removal and achieving a nearly defect-free clean surface.

Origins of wear-induced tungsten corrosion defects in semiconductor manufacturing during tungsten chemical mechanical polishing

During chemical mechanical polishing (CMP) process optimization, a unique corrosion defect was identified in the tungsten (W) contact plugs, which were investigated to develop practical solutions to improve CMP mass productivity. The corrosion defect occurred in the absence of external incident energy and was observed to occur only at the W plugs connected to the P+/n-well close to the wafer edge. To examine the root cause of the corrosion, a series of experiments was carried out at each W CMP step, using in-line defect inspection. Additional experiments were conducted using on-line inductively coupled plasma mass spectrometry (ICP-MS) to understand pH- and potential-dependent electrochemical dissolution behaviors of W. Experimentally, W corrosion was confirmed to be exacerbated if the surface oxide of the W plugs is removed by the deionized water (DIW) rinsing step under wafer pressurization, then exposed to DIW and alkaline cleaning solution. Although the DIW rinsing step is commonly performed to clean polishing pads right after the main polishing, a small amount of applied pressure (0.5 psi) without slurry supply can lead to corrosion defects. This wear-induced corrosion of the W plugs can be prevented by removing the applied pressure during the post DIW rinsing step of W CMP.

Design and construct alkali-responsive nanocontainers for self-healing thin-film composite reverse osmosis membranes

Poor chlorine resistance is a major factor affecting service life of aromatic polyamide reverse osmosis membranes. Herein, alkali-responsive polymer nanocontainers are designed and constructed via emulsified cross-linking and electrostatic self-assembly of sodium alginate, chitosan, and polyaspartic acid around chitosan nanoparticles, and the nanocontainer is integrated into polyamide layer of thin film composite membranes. The nanocontainer does not only provide more channels for water molecules to improve membrane permeability, but also during routine alkaline washing process, polyaspartic acid at the outer layer reacts with alkaline agent to release healing agents: sodium alginate and chitosan to heal damaged sites to restore membrane performances. For example, with the addition of 0.005 wt% nanocontainers, water flux was increased by 32.8% compared to pristine membranes without sacrificing NaCl rejection. After soaking in alkaline cleaning solution, NaCl rejection of the membrane degraded by 2000 ppm active chlorine can be recovered by 97.3%. Therefore, self-healing nanocontainers can greatly improve chlorine resistance, water flux, and stability of polyamide reverse osmosis membranes.

Composite complex agent based on organic amine alkali for BTA removal in post CMP cleaning of copper interconnection

The combination of FA/OII chelating agent and double complexing agent ammonium citrate can shift the ionization to the right (the dissolution of Cu-BTA), effectively break the Cu-N bond, and accelerate BTA removal on the copper surface. • Ammonium citrate's nucleophilic attack may occur near C2 and O4 atoms. • The electrophilic attack may occur near N22 and N26 atoms. • The pH value of the cleaning solution is stable at 10.24 for optimal removal of BTA. • Effect and mechanism of composite complex agent were studied by electrochemical, contact angle, SEM, FTIR and XPS. • Composite complex agent can complex copper ions, form copper amine complex and break the ionization balance of Cu-BTA. Benzotriazole (BTA) is a common corrosion inhibitor in chemical mechanical polishing (CMP). It is also the main pollutant to be removed in post CMP cleaning. In this paper, a new type of alkaline cleaning solution based on composite complexing agent was proposed for BTA removal. The optimal concentration and pH value of the cleaning solution were explored using electrochemical measurement and contact angle measurement. When the components were 200 ppm FA/OII chelating agent and 0.1 vol% ammonium citrate (pH = 10.24), BTA residue on copper surface can be effectively removed. Density Functional Theory (DFT) proved that ammonium citrate's nucleophilic attack may occur around C2 and O4 atoms, respectively. The electrophilic attack of ammonium citrate may occur around N22 and N26 atoms, respectively. The results of scanning electron microscopy (SEM) showed that a lower surface roughness was obtained after cleaning. Fourier transform infrared spectrometer (FTIR) and X-ray photoelectron spectroscopy (XPS) measurements confirmed that the cleaning solution could complex copper ions, break the ionization balance of Cu-BTA and accelerate its dissolution, so as to remove BTA effectively.

New insights into effect of alkaline cleaning on fouling behavior of polyamide nanofiltration membrane for wastewater treatment

Membrane fouling is an intractable issue in wastewater treatment by nanofiltration (NF) membrane, and alkaline cleaning is the most effective approach to remove organic fouling on NF membrane. However, it was found that pore swelling of NF membrane induced by alkaline cleaning might reduce cleaning efficiency, and it is never quantified and its effect on membrane fouling behavior is still mysterious. In this work, membrane pore swelling effect (~9.7%, increment of effective pore size) induced by alkaline cleaning (pH 11) is confirmed and its effect on fouling behavior of the polyamide NF membrane is investigated based on experimental and modelling results. It is found that the alkali-induced pore swelling phenomenon would disappear after water filtration at neutral pH for 30 min, and if such cleaned membrane is faced by the small foulants during this pore shrinkage period, the concentration polarization and membrane fouling would be severer, and the subsequent alkaline cleaning is less effective because more foulants enter the enlarged pores and are tightly embedded in the membrane. Thus, the irreversible fouling of the NF membrane increases from 20% to 40% while its permeability recovery declines from 100% to 67% after six fouling/cleaning cycles. When an anionic surfactant sodium dodecyl sulfate (SDS, 10 mM) is added in the alkaline cleaning solution, the adsorption of SDS in/on the membrane can not only improve its hydrophilicity and negative charge, but also quickly eliminate the alkali-induced pore swelling effect and avoid the accumulation of foulants in the pores, thereby enhancing the antifouling performance of the NF membrane. Using the alkaline SDS cleaning, the irreversible fouling of the NF membrane maintains below 10% while its permeability recovery keeps above 100% in six continuous fouling/cleaning cycles.

Effect of EDTA-based alkaline cleaning solution on TAZ removal in post CMP cleaning of copper interconnection

1,2,4-triazole (TAZ) has been proved to be an alternative to Benzotriazole (BTA) as an corrosion inhibitor in chemical mechanical polishing (CMP) of multilayer copper interconnection for integrated circuit. It has also become the main object to be removed in post CMP cleaning. In this paper, a new type of alkaline cleaning solution based on EDTA was proposed to remove TAZ on copper surface. The optimal concentration ratio and pH value of the alkaline cleaning solution were explored using electrochemical measurement, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) and scanning electron microscopy (SEM). When the components of the cleaning solution were 25mg/L ethylenediaminetetraacetic acid (EDTA) and 600mg/L dodecylbenzene sulfonic acid (LABSA) (pH = 10.6), the Cu-1,2,4-trazole compounds formed by TAZ contamination on the copper surface can be effectively removed. Density Functional Theory (DFT) was used to confirm that EDTA could break the bond of Cu-1,2,4-triazole through the strong interaction between O16、H2、H36 and copper surface. No corrosion was observed on the cleaned copper surface and surface roughness was lower, which indicated that the cleaning solution was suitable for the removal of TAZ on copper surface.

Research Treatment Studies for Cleanable Waste Water for Cleaning Pipes


 
 
 Currently, many methods of treating waste water are known using various lubricating coolant compositions, but there is no universal treatment method. The most suitable ways of reducing the harmful impact of waste water in the metallurgical industry on the water environment are 1) the local treatment of waste water of various compositions, 2) the removal or reduction of the total amount of waste treatment liquid emissions as a result of their regeneration, and 3) reuse of treated waste water in closed water circulation systems and technical water supply to enterprises. During production of bimetallic finned tubes by cold deformation method, alkaline cleaning solutions are used to clean the surface from lubricating-cooling liquid. As a result, there is a need to dispose of spent liquids. The spent detergent solution is a three-phase emulsion. The upper layer is oil-oil products, medium liquid with increased PH index, and aluminates precipitate. A spent emulsion, i.e. an end-of-life emulsion that has lost its functional and operational properties, needs to be decomposed and disposed of.
 Keywords: finned bimetallic tube, air cooler, lubricating coolant, oil – emulsion
 
 

Experimental validation and molecular dynamics simulation of removal of PO residue on Co surface by alkaline cleaning solution with different functional groups

Potassium oleate (PO) is a promising inhibitor for cobalt wiring chemical mechanical polishing (CMP) of integrated circuit (IC) to replace benzotriazole (BTA). The insoluble Co-PO complex formed on cobalt surface in the process of CMP become the main organic residues object of post CMP cleaning. In this paper, tetramethylammonium hydroxide (TMAH) and three complexing agents with different functional groups were used to form alkaline cleaning solution to remove the organic residue of Co-PO complex on cobalt surface. The cleaning effect was characterized by contact angle, electrochemistry, atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS). Furthermore, the cleaning mechanism was revealed by molecular dynamics simulation based on density functional theory (DFT). The results show that the carboxyl group in Ethylenediamine tetraacetic acid (EDTA) is more easily to chelate with Co(II), which could break the Co-PO complex to remove PO on the cobalt surface. The mechanism of removing corrosion inhibitors by complexing agents will be helpful to the post-CMP cleaning of new generation Cobalt wiring.

Compressed earth blocks stabilized with glass waste and fly ash activated with a recycled alkaline cleaning solution

Sustainable alternatives are increasingly demanded as a sound response, from the construction industry, to the worldwide growing concerns with the environment. Such effort is justifiable by the degree of the contribution of this human activity to the problem, and it has thus propelled the development of a major trend in terms of funded research. The study reported in this paper focused on the physical-mechanical properties of compacted earth blocks formed by a common Portuguese silty clay (as the mineral skeleton), stabilized with a sustainable alkali activated cement exclusively produced from wastes and residues, including coal fly ash and glass waste, in a 50/50 wt ratio combination, and activated with an alkaline solution from the aluminium industry, using activator/precursor weight ratios of 0.50, 0.57 and 0.75. After optimising the alkaline activated cement (AAC), the AAC/Soil blocks were fabricated, using the response surface method to define their composition based on curing periods of 28 and 180 days at controlled ambient temperature. Uniaxial compressive strength (UCS) and several durability tests were performed, and the material was characterised using FTIR and SEM. The results evidenced the effectiveness of the alkaline cementing agent in forming a binding matrix for the soil particles. An average compressive strength of 17.23 MPa, in unsaturated conditions, was obtained for the blocks. The newly formed soil-binder structure was very capable to withstand wetting and drying cycles, ice-thaw cycles and erosion. The microstructure of the material was further analysed, using scanning electron microscopy and energy dispersive spectroscopy. The results demonstrated the real possibility of using this type of cement as a viable alternative to traditional soil stabilisation binders used in earth construction.

Synergistic effect of composite complex agent on BTA removal in post CMP cleaning of copper interconnection

Benzotriazole (BTA) is a common corrosion inhibitor for chemical mechanical polishing (CMP) of multilayer copper wiring of integrated circuit. It is also the main object to be removed in post CMP cleaning. In this study, a new type of alkaline cleaning solution based on composite complex agent was proposed to remove BTA effectively. The optimal cleaning concentration ratio and pH value of the new complex complexing agent were explored through electrochemical measurement and contact angle measurement. When the components of cleaning solution were 250 ppm diethylenetriaminepentaacetic acid (DTPA), 1000 ppm FA/OII chelating agent and 100 ppm polyethyleneimine (PEI) (pH = 10.5), the contact angle of copper surface contaminated by BTA can be reduced from 58.1° contaminated by BTA to 25.1°. Density Functional Theory (DFT) proved that DTPA could reduce the adsorption energy of BTA on copper surface. The result of atomic force microscopy (AFM) and scanning electron microscopy (SEM) on copper surface showed that composite complexing agent does not cause corrosion and a lower surface roughness was obtained after cleaning. X-ray photoelectron spectroscopy (XPS) results verified that the cleaning solution could complex copper ions, break the Cu-N bond and promote the decomposition of the Cu-BTA adsorbed chemically on Cu2O, so as to remove BTA effectively.

Application of membrane distillation to anaerobic digestion effluent treatment: Identifying culprits of membrane fouling and scaling

Membrane distillation (MD) has great potential in the treatment of high-salinity and low-biodegradability wastewater, but membrane fouling restricts its real applications. In this work, MD was applied to treat anaerobic digestion effluent, and the feed pH was adjusted to investigate the membrane organic fouling and inorganic scaling. The results show that the fouling of MD membranes during the treatment of anaerobic digestion effluent was substantially alleviated at a low feed pH (pH=5). Scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS) and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) were used to characterize the fouled membranes. The MD membrane scaling was primarily attributed to the deposition of calcium-, magnesium-, phosphate-, and silicon-related inorganic compounds during the treatment of cow dung anaerobic digestion effluent. Feed acidification significantly decreased inorganic scaling as well as fouling by organic matter, and organic fouling dominated the fouling process in the low-pH environment. By comparing the components in acid and alkaline cleaning solutions, it was found that the deposition of organics on the membranes via adsorption to inorganic scaling was the primary cause of more severe organic fouling with increasing feed pH. Hence, restricting inorganic scaling could be an effective way to control MD membrane fouling by organics during treatment of anaerobic digestion effluent.

Sustainable alkaline activation of fly ash, aluminium anodising sludge and glass powder blends with a recycled alkaline cleaning solution

Introduction of new residues and wastes in the development of alkaline activated materials is a major concern regarding the spreading and dissemination of this technique. Such increase in the spectrum of available raw materials will decrease the need for long-distance transportation of the more traditional precursors that have been tirelessly used in the past two decades (e.g. fly ash, blast furnace slag). Additionally, the use of commercial activators severely hinders its environmental and financial performance, promoting the need to develop waste-based activators. In this paper, wastes from the aluminium anodising and extrusion processes and from the production of optical lenses were combined with low-calcium fly ash, to produce binders exclusively made from wastes and residues. The performance was assessed through uniaxial compression strength tests, which were accompanied by the monitorisation of several physical properties, including temperature, pH and weight; and by a thorough microscopic analysis, including scanning electron microscopy, coupled with energy dispersive spectroscopy, and x-ray diffraction, for mineralogy characterisation. Results show that the addition of glass powder and aluminium anodising sludge to class-F fly ash optimised the final precursor, which was then successfully activated with a disposed solution, originally used to clean the aluminium extrusion steel dies. The inclusion of soluble silicon and aluminium in the precursor raised the compression strength after short-term curing, compared with pastes prepared only with fly ash.