Removal behavior of Cu(II) during Cr(VI) reduction by cast iron powder in absence and presence of ultrasound

ABSTRACT

Cu(II) is an important and typical heavy metal ion in the wastewater containing Cr(VI), and its removal during Cr(VI) reduction by zero valent iron (ZVI) may make it separately be recovered as a kind of copper resource. In this study, the removal behavior of Cu(II) during Cr(VI) reduction by cast iron powder in absence and presence of ultrasound was investigated by atomic absorption spectrometry (AAS), X-ray powder diffractometer (XRD), scanning electron microscope-energy dispersion spectrum (SEM-EDS) and X-ray photoelectron spectroscopy (XPS). The AAS tests indicated that the ultrasound could not only obviously enhance the removal of Cu(II) but also improve the reduction rate of Cr(VI). The XRD and SEM-EDS analyses showed that Cu(II) in the solution was reduced to metallic copper and then was deposited at the surface of ZVI. The ultrasound could remove the Fe-Cr oxides and hydroxides at the ZVI surfaces, resulting in the active surfaces of iron increased. The XPS analyses demonstrated that the surface of metallic copper would be transformed into the film of copper oxide (CuO) in the ultrasound system. The obtained metallic copper and copper oxide could be recovered alone by traditional method of the acid pickling.     

In situ micro-Raman spectroscopy to investigate pitting corrosion product of 1024 mild steel in phosphate and bicarbonate solutions containing chloride and sulfate ions

The nature of the corrosion products generated by localized attack on 1024 mild steel have been investigated in the presence of chloride and/or sulfate ions in bicarbonate and phosphate aqueous solutions. A spectroelectrochemical cell was used for in situ measurements of the Raman spectra of the corrosion products generated during pitting. These products were identified as the so-called green rust compounds. The assignment of the hydroxyl groups in green rust is confirmed by isotopic substitution. The composition of the green rust generated in bicarbonate or phosphate solution containing chloride and/or sulfate ions has been determined. A correlation between the green rust composition and the electrochemical behaviour after the initiation of pitting has been noted and discussed.     

Functionalized galactoglucomannan‐based hydrogels for the removal of metal cations from aqueous solutions

New types of hydrogels derived from O‐acetyl galactoglucomannan (AcGGM) hemicellulose have been synthesized and characterized. The objective of this work was to analyze the sorption capacity (S) of three types of hydrogels containing AcGGM derivatives incorporated into the carboxylic groups of the polymer chain in the AA hydrogel, sulfonic groups in the APA hydrogel, and amide groups in the acrylamide (Aam) hydrogel. These hydrogels are capable of interacting and removing ions such as cadmium [Cd(II)], copper [Cu(II)], lead [Pb(II)], nickel [Ni(II)], and zinc [Zn(II)]. The results show that AA and Aam hydrogels had a lower sorption capacity of ions compared to the APA hydrogel, which had a high sorption capacity. The maximal sorption capacity was determined by the successive enrichment method, obtaining Pb(II) amount of 48.3 mg/g of AA hydrogel, 65.8 mg/g of APA hydrogel, and 40.8 mg/g of Aam hydrogel. Hence, Pb(II) ions are greatly retained by the three hydrogels. These results are promising for the development of new materials with potential applications in metal ion removal. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44093.     

Application of electrochemical noise to evaluate outdoor atmospheric corrosion of copper after relatively short exposure periods

This study focused on the application of electrochemical noise to assess the protection level of corrosion products formed on copper during relatively short exposure time in different outdoor atmospheres. Electrochemical noise, cathodic reduction measurements and gravimetric (mass loss) analysis were applied to copper samples exposed at urban and rural/industrial areas in Cuba for 4 months. Measurements of Electrochemical current noise indicated that the poorest protective corrosion products were formed on samples exposed to atmospheres with high concentration of H₂S which agreed with the corrosion rate determined by mass loss and electrochemical chronopotentiometry (cathodic reduction). The electrochemical noise methodology proposed in this work showed acceptable and reproducible results by using an electrochemical cell in which the electrolyte was formed by a distilled-water wetted cloth in contact with the compounds present on a corroded metallic surface. This methodology indicated that the corrosion protection level of the corrosion products formed on copper is related to the corrosivity of the atmosphere.     

一种通用型微乳化金属切削液的研制

通过正交实验和配方优化研制出具有自主品牌的,适用于金属材料：不锈钢、铜、铝及铝合金、钛合金等材料的切削、磨削、钻孔及数控加工的微乳化切削液,性能达到或超过国内外同类产品,对机床、工件无锈蚀,对人体和生态无害,具有较好的防锈性和极压性。     

Influence of Copper Ions on Adherence of Vitreous Coatings to Stainless Steel

An investigation was made of the effect of copper oxide in promoting the adherence of vitreous coatings to AISI type 321 stainless steel. It was found that copper ions in the coating produced a significant increase in adherence on both pickled and sandblasted surfaces but that the effect of the copper decreased with increased firing temperature and increased firing time for the pickled specimens. X-ray examination of specimens revealed that the copper ions were reduced to metallic copper near the interface during firing; however, examination of sections with the metallographic microscope showed no selective corrosion of the stainless-steel surface. It was observed that the curve obtained when plotting the copper oxide content of the coating against the adherence index was of the same type as that obtained for cobalt oxide on ingot iron.     

Corrosion of carbon steel influenced by anaerobic biofilm in natural seawater

The bacteria in the anaerobic biofilm on rusted carbon steel immersed in natural seawater were characterized by culturing and molecular biology techniques. Two types of anaerobic bacterium, sulfate-reducing bacteria (SRB) Desulfovibrio caledoniensis and iron-reducing bacteria Clostridium sp. uncultured were found. The compositions of the rust layer were also analyzed and we found that iron oxide and sulfate green rust were the major components. To investigate the corrosion mechanisms, electrochemical impedance spectra was obtained based on the isolated sulfate-reducing bacteria and mixed bacteria cultured from rust layer in laboratory culture conditions. We found that single species produced iron sulfide and accelerated corrosion, but mixed species produced sulfate green rust and inhibited corrosion. The anaerobic corrosion mechanism of steel was proposed and its environmental significance was discussed.     

Characterization of copper oxidation by linear potential sweep voltammetry and UV-Visible-NIR diffuse reflectance spectroscopy

The aim of this study was to characterize the compounds grown on copper during oxidation at low temperature (T<573 K) in air by electrochemical and optical methods. The following oxides have been characterized: a precursor Cu _x O of mixed valency character, a non stoichiometric cuprous oxide, CuO and its precursor. The mechanism of reduction has been established for layers containing CuO and a non stoichiometric copper(I) oxide. CuO is reduced before cuprous oxide. In complicated cases, it is impossible to draw conclusions from the characteristics of the electrochemical reduction (the first step of CuO reduction and the reduction of Cu(I) species specific of the non-stoichiometry are observed at the same potential). Nevertheless, the association of a non-destructive technique such as diffuse reflectance spectroscopy and electrochemical methods allows identification of the different species present in corrosion layers on copper surfaces.     

Classification of suppressor additives based on synergistic and antagonistic ensemble effects

Three fundamental types of suppressor additives for copper electroplating could be identified by means of potential transient measurements. These suppressor additives differ in their synergistic and antagonistic interplay with anions that are chemisorbed on the metallic copper surface during electrodeposition. In addition these suppressor chemistries reveal different barrier properties with respect to cupric ions and plating additives (Cl, SPS). While the type-I suppressor selectively forms efficient barriers for copper inter-diffusion on chloride-terminated electrode surfaces we identified a type-II suppressor that interacts non-selectively with any kind of anions chemisorbed on copper (chloride, sulfate, sulfonate). Type-I suppressors are vital for the superconformal copper growth mode in Damascene processing and show an antagonistic interaction with SPS (Bis-Sodium-Sulfopropyl-Disulfide) which involves the deactivation of this suppressor chemistry. This suppressor deactivation is rationalized in terms of compositional changes in the layer of the chemisorbed anions due to the competition of chloride and MPS (Mercaptopropane Sulfonic Acid) for adsorption sites on the metallic copper surface. MPS is the product of the dissociative SPS adsorption within the preexisting chloride matrix on the copper surface. The non-selectivity in the adsorption behavior of the type-II suppressor is rationalized in terms of anion/cation pairing effects of the poly-cationic suppressor and the anion-modified copper substrate.Atomic-scale insights into the competitive Cl/MPS adsorption are gained from in situ STM (Scanning Tunneling Microscopy) using single crystalline copper surfaces as model substrates.Type-III suppressors are a third class of suppressors. In case of type-I and type-II suppressor chemistries the resulting steady-state deposition conditions are completely independent on the particular succession of additive adsorption. In contrast to that a strong dependence of the suppressing capabilities on the sequence of additive adsorption (“first comes, first serves” principle) is observed for the type-III suppressor. This behavior is explained by a suppressor barrier that impedes not only the copper inter-diffusion but also the transport of other additives (e.g. SPS) to the copper surface.     

An experimental investigation of the influence of the grain size of the metal surface on pool boiling heat transfer

The influence of the grain size of metallic surfaces on nucleate boiling was investigated experimentally. Surfaces of electrodeposited copper, nickel, brass and chromium were studied with particular emphasis on copper (146 grains per inch to 1678 grains per inch). The pool boiling heat transfer studies were conducted by transferring heat produced electrically through a 6-in. diameter heating surface to a pool of boiling water contained in a glass boiler. A log-log plot of the Q/A versus δT_m data showed a definite effect of the grain size of the surface on nucleate boiling heat transfer, the heat transferred at a given δT_m increasing as the grain size increased. For copper plated surfaces, the Rohsenow Equation for nucleate pool boiling gave values for C_st and r, which showed a linear relationship when plotted separately against the number of grains per unit length of the surface. A slightly modified form of the Rohsenow correlation has been proposed which takes into account the influence of the grain size of the surface metal for predicting boiling heat transfer.     

Preparation of a hydroxyethyl–titanium dioxide–carboxymethyl cellulose hydrogel cage and its effect on the removal of methylene blue

A novel TiO₂ hydrogel cage model was built for the removal of methylene blue (MB), an organic pollutant. This TiO₂ hydrogel cage was prepared with the biomass materials of hydroxyethyl cellulose (HEC) and carboxymethyl cellulose (CMC), and this hydrogel cage structure was characterized by scanning electron microscopy, transmission electron microscopy, and X‐ray diffraction. The contents of the encased TiO₂ and its swelling properties with different CMC proportions of this hydrogel cage were studied to obtain a suitable crosslinking network structure and optimal synthesis conditions. Compared to an equivalent amount of pure TiO₂, the much higher removal efficiency of MB with our prepared TiO₂ hydrogel cage was attributed to the synergistic effect of the photocatalytic degradation for TiO₂ and the adsorption enrichment for cellulose hydrogels. Furthermore, the adsorption kinetics of the intraparticle diffusion model were used to study the adsorption enrichment process of the TiO₂ hydrogel cage. In addition, on the basis of the results of photocatalytic degradation and recycling experiments, excellent performances with respect to self‐cleaning, regenerative ability, and easy recovery, were shown for this HEC–TiO₂–CMC cage material, which demonstrated ideal application potential for MB removal. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44925.     

Robust polymeric hydrogel using rod‐like amidodiol as crosslinker: Studies on adsorption kinetics and mechanism using dyes as adsorbate

Herein, we report the preparation of robust polyacrylic acid hydrogel using rod‐like amidodiol as physical crosslinker. Polyacrylic acid–amidodiol hydrogels were characterized for its chemical structure, rheology, swelling, diffusion, and adsorption properties. Kinetics and mechanism of adsorption were investigated by UV–visible spectroscopy using dyes such as rhodamine 6G and methylene blue as adsorbate. Results suggested pseudo second‐order kinetics of multilayer adsorption and hydrogel could retain its shape even after swelling. Effect of amidodiol on the adsorption of dyes was investigated. Extent of interaction between adsorbate–adsorbate and adsorbent–adsorbate was studied using Gile's model. The generated results may provide a low cost simple technology for developing robust polymeric hydrogel adsorbent. The adsorption characteristics results can be exploited for setting up pilot plant adsorbent for the removal of such organic toxic materials. Finally, we have demonstrated its application for the removal of dyes from waste water collected from textile and paper industries. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40908.     

Heavy metal removal using hydroxypropyl cellulose and polyacrylamide gels,kinetical study

In this article we report the removal of Pb, Ni and Cu using a hydrogel made with hydroxypropyl cellulose (HPC) and polyacrylamide (PAAm). The hydrogel successfully removed those metals, as shown by the results of atomic absorption spectroscopy; the polymer removed 53% of Pb, 52% of Ni and 51% of Cu. Different pHs were tried for these polymers. The highest metal removal was found at 40°C. The adsorption kinetics fitted Langmuir and Freundlich isotherms. Metal particles were detected on the hydrogel with electron microscopy and energy–dispersive X–ray spectroscpy, confirming that the gel removed the metals from the testing solutions. This polymer is a good option for treating wastewater and industrial waters as it removes metals and is composed of nontoxic materials. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43285.     

Effects of residual white rust of inorganic zinc silicate primer on corrosion protection of epoxy-coated carbon steel

Inorganic zinc silicate primer is widely used in shipbuilding as a preconstruction primer (or shop primer) on steel plates; however, white rust of zinc is formed on inorganic-zinc-silicate-coated steel surfaces exposed to outdoor conditions such as rain and humidity. In this study, effects of residual white rust of inorganic zinc silicate primer on corrosion protection of epoxy-coated carbon steel were examined by water ballast simulation and condensation chamber tests. Pull-off adhesion, blistering, and cathodic disbondment tests were also performed for the same purpose. Test results clearly indicated that the residual white rust did not affect the corrosion protection when the steel surface was treated with light to heavy sweep blasting.     

微乳型油墨清洗剂的研制与清洗性能

研制了一种由乳化剂、表面活性剂、溶剂、复合缓释剂及其它助剂构成的O/W型微乳液,研究了温度、水与清洗剂的复配比对清洗剂使用性能的影响。结果表明,该微乳液可替代汽油、煤油用于印刷机件上油墨的清洗,且防锈缓蚀和安全性能超过汽油、煤油等溶剂型清洗剂;清洗剂的使用温度和水与清洗剂的复配比对微乳型油墨清洗剂的使用性能有较大影响,适宜的使用温度以30℃为宜,适宜的水与清洗剂的复配比为(3.0~4.0)∶1.0;在水与清洗剂的复配比为4.0∶1.0,清洗温度不低于25℃的条件下,对油墨的去除率超过95%。     

Silane-modified polyvinylimidazole(1) for corrosion protection on copper at elevated temperatures

Silane-modified N-polyvinylimidazole [PVI(1)] copolymers have been synthesized from various mole ratios of γ-methacryloxypropyltrimethoxysilane (γ-MPS) and N-vinylimidazole, VI(1). Fourier transform infrared reflection-absorption spectroscopy (FTIR-RAS) is used to investigate the modified PVI(1) on copper surfaces. The silane-modified PVI(1) has good corrosion protection and adhesion promotion capabilities for copper substrate under severe environments. The relationship between coating thickness and corrosion protection is studied at elevated temperatures. The relationship between the mole ratio of comonomers and the corrosion processes of a copper surface has also been investigated at elevated temperatures. The corrosion protection improves drastically with increased VI(1) content. An adhesion study of the silane-modified PVI(1) film on a copper surface is also carried out using the ASTM adhesive tape test. From the adhesion strengths between the modified PVI(1) films and copper surface, it has been observed that modified PVI(1) acts as an adhesion promoter and does not depend on the mole ratio of γ-MPS/VI(1) within the range of this experiment. Good adhesion of an anticorrosion coating is important for the corrosion protection of a copper surface. © 1993 John Wiley & Sons, Inc.     

Synthesis,characterization and corrosion protection of poly-4-methyl-3-mercapto-1,2,4-triazole/TiO2 composite on copper

The present work deals with the electrochemical synthesis of poly-4-methyl-3-mercapto-1,2,4-triazole (p-MMTA)/TiO₂ composite on metallic copper to evaluate its corrosion protection. The composite was characterized by FT-IR, cyclic voltammetry, X-ray diffraction and energy dispersive X-ray analysis. The distribution of inorganic particles in the polymeric matrix was evidenced from the scanning electron microscopic studies. The corrosion performance of composite coating was evaluated by electrochemical impedance spectroscopy and Tafel polarization measurements in 3.5 % NaCl medium. The p-MMTA/TiO₂ composite showed an excellent corrosion protection ability, which was evidenced from the results of electrochemical measurements. The enhanced ability could be due to the barrier effect of composite coatings against corrosive species and also due to the synergistic effect between organic polymer and inorganic particles.     

Electrochemical remediation of metal-bearing wastewaters Part II: Corrosion-based inhibition of copper removal by iron (iii)

A hitherto undocumented inhibition to electrodeposition of Cu(ii) from dilute (<200 mg L–1) wastewaters was traced to the presence of Fe(iii) at concentrations comparable to those of copper ion. This inhibition was found to differ from heterogeneous side-reduction of Fe(iii) that is well known to decrease faradaic efficiency for copper removal. Based on bench-scale electrolysis as well as cyclic voltammetry studies, an inhibition mechanism was qualitatively identified that involved copper corrosion by Fe(iii). This corrosion process was found to be strongly favoured by sluggish heterogeneous reduction of Fe(iii) at carbon electrode materials. One procedure shown to substantially improve copper removal from solutions demonstrating corrosion inhibition was alkali precipitation of iron. Real mine drainage wastewater that was pretreated in this manner was consistently depleted of copper by flow-through electrolysis to levels below 50 g L–1.     

Nanocomposite hydrogels for selective removal of cationic dyes from aqueous solutions

Removal of organic dyes from waste water has received a significant attention in recent years. In this work, a set of nanocomposite hydrogels (NHs) were prepared and their capacity to absorb crystal violet (CV), a cationic dye, and acid yellow‐23 (AY), an anionic dye, from aqueous solutions was determined. NHs were prepared by in situ formation of Fe₃O₄ magnetic nanoparticles (MNPs) inside poly(acrylamide‐co‐4‐styrene sulfonic acid sodium salt) (P[AAm‐co‐SSA]) hydrogel matrices. The dye absorption capacity of the magnetic NHs (MNHs) was compared with simple hydrogels (hydrogels or SHs) without the MNPs The prepared hydrogels were characterized by FTIR, XRD, thermogravimetric analysis, high resolution TEM, field emission SEM, and vibrating sample magnetometer measurement. From HRTEM, it was confirmed that the prepared MNPs in hydrogel matrices were in the size range of about 8 to 10 nm. The MNHs showed greater swelling behavior as well as greater removal efficiency of cationic dye from aqueous solutions in comparison to the SHs. With increase of SSA mole percentage, dye removal efficiency was also increased for both types of hydrogels. The present study indicates that the hydrogels containing MNPs can be potentially used as an efficient absorbent material for removal of cationic dyes from waste water. POLYM. ENG. SCI., 56:776–785, 2016. © 2016 Society of Plastics Engineers     

环保型除锈剂的研究

传统无机酸酸洗对钢铁基体的腐蚀性强,并且会产生酸雾。制备出一种环保型除锈剂。确定了除锈剂的成分,并分析了各成分的作用。研究了有机酸、缓蚀剂、表面活性剂、渗透剂对除锈时间和除锈效果的影响。