In this study, a novel biochar-supported zero valent iron (BC-nZVI) was synthesized through a green method. A high performance on the simultaneous removal of Cu²⁺ and bisphenol A (BPA) by a combination of BC-nZVI with persulfate (BC-nZVI/PS) system was successfully achieved. The simultaneous efficiencies of Cu²⁺ and BPA could reach 96 and 98% within 60 min, respectively. Both HO• and SO₄•⁻ were two major reactive species in BC-nZVI/PS system, and SO₄•⁻ was primary radical responsible for the degradation of BPA. Four kinds of Cu species, such as Cu(OH)₂, CuO, Cu₂O and Cu⁰ were generated via the adsorption and reduction of the BC-nZVI, whereas six kinds of products of BPA including p-isopropenyl phenol and 4-isopropylphenol were generated via the combined oxidation of SO₄•⁻ and HO•. The possible reaction mechanism for the simultaneous removal of Cu²⁺ and BPA by BC-nZVI/PS system contained a synergistic effect between the reduction of Cu²⁺ and the oxidation of BPA. This is the first report on the feasibility of the remediation of coexistence of heavy metal and organic compound in aquatic environment using the BC-nZVI/PS system.

The intensive use of Cu-based pesticides in agriculture could have an unintended impact on the ecosystems and human health via different exposure pathways. This paper presents the results of experiments involving colloidal stability, aggregation, and dissolution of Cu₂O commercial pesticide under various environmental conditions in view of ecological implications. The investigated pesticide contains ∼750 g kg⁻¹ Cu (75% weight of product), Cu₂O particles with sizes < 1 μm, and nominal size fraction of Cu₂O nanoparticles. The co-presence of Ca²⁺ (20 mM) and humic acid (HA, 15 mg L⁻¹) significantly modulates (p < 0.001) the colloidal stability and mobility of particles. The dissolution of Cu at pH 5.5 was about 85%, 90%, and 75% weight more than the dissolution of Cu at pH 7.0, pH 8.5, and pH 7.0 and pH 8.5 combined, respectively in all dispersions. However, increasing HA content from 0 to 15 mg L⁻¹ reduced the dissolution of Cu by 56%, 50%, and 40% weight at pH 5.5, 7.0, and 8.5, respectively. Thus, pH below 7.0 is a critical factor to control the dissolution and bioavailability of Cu that may pose ecotoxicity and environmental pollution, whereas pH above 7.0 and the presence of HA attenuate the pH effect. These findings provide insight into how the potential mobility and bioavailability of Cu is modulated by the water chemistry under various environmental scenarios and media.

Antifouling paints incorporate biocides in their composition seeking to avoid or minimize the settlement and growing of undesirable fouling organisms. Therefore, biocides are released into the aquatic environments also affecting several nontarget organisms and, thus, compromising ecosystems. Despite global efforts to investigate the environmental occurrence and toxicity of biocides currently used in antifouling paints, the specific active ingredients that have been used in commercial products are poorly known. Thus, the present study assessed the frequencies of occurrence and relative concentrations of biocides in antifouling paint formulations registered for marketing worldwide. The main data were obtained from databases of governmental agencies, business associations, and safety data sheets from paint manufacturers around the world. The results pointed out for 25 active ingredients currently used as biocides, where up to six biocides have been simultaneously used in the examined formulations. Cuprous oxide, copper pyrithione, zinc pyrithione, zineb, DCOIT, and cuprous thiocyanate were the most frequent ones, with mean relative concentrations of 35.9 ± 12.8%, 2.9 ± 1.6%, 4.0 ± 5.3%, 5.4 ± 2.0%, 1.9 ± 1.9%, and 18.1 ± 8.0% (w/w) of respective biocide present in the antifouling paint formulations. Surprisingly, antifouling paints containing TBT as an active ingredient are still being registered for commercialization nowadays. These results can be applied as a proxy of biocides that are possibly being used by antifouling systems and, consequently, released into the aquatic environment, which can help to prioritize the active ingredients that should be addressed in future studies.

Owing to high treatment efficiency under neutral condition and no extra energy required, copper-mediated activation of persulfate (PS) has been widely used for the degradation of refractory organic pollutants in water. The dispersion stability of copper nanoparticle in water, however, remains a great challenge. Meanwhile, chemical oxidative modification of graphene oxide (GO) can improve the dispersion stability of GO in water. In this paper, cuprous oxide (Cu₂O) was deposited on the surface of GO. GO/Cu₂O nano-composites with different mass ratios, i.e., m(GO):m(Cu₂O) of 1:2, 1:5, 1:10, and 1:25, were prepared. When m(GO):m(Cu₂O) was 1:2, the amount of GO/Cu₂O nano-composite was 1.00 g/L and CPDS:CDCF was 15:1, and the catalytic degradation rate of diclofenac (DCF) was up to 90%. Corresponding physicochemical properties of the resulting samples were comprehensively characterized by using SEM, TEM, XRD, Raman, FT-IR, and XPS. DCF degradation by activating peroxydisulfate (PDS) via GO/Cu₂O nano-composite was also investigated in detail. It is found that the synergistic effect, namely GO adsorption and multivalent copper ion electron transfer, makes GO/Cu₂O nano-composite reveal higher reactivity. Moreover, GO/Cu₂O nano-composite possesses good stability in consecutive cycling test. EPR analyses shows that ·OH and SO₄·⁻ radicals are involved in DCF degradation. It is indicated that the DCF degradation process contain hydroxylation and the cleavage of C-N bond, which is explored by GC–MS. In our research, well-dispersed GO/Cu₂O nano-composite with high capacity and good cycling stability was fabricated successfully. Compared with pure Cu₂O nanoparticle, GO/Cu₂O nano-composite exhibits the better performance for DCF removal. A novel well-dispersed cuprous oxide (Cu₂O) deposited on surface of GO was fabricated with high catalytic performance. Its heterogeneous activation of peroxydisulfate (PDS) for diclofenac (DCF) degradation was investigated. GO/Cu₂O nano-composite was proved high capacity and good cycling stability. Meanwhile, the possible DCF degradation pathway was explored. Compared with pure Cu₂O nanoparticle, GO/Cu₂O nano-composite exhibits better performance for DCF removal.

Ni, Cu, and Ni-Cu metal oxides supported on granular activated carbon (GAC) were synthesized and used in catalytic ozonation of heavy oil produced water. The effect of preparation conditions on their catalyst composition, catalyst structure, and catalytic activity was investigated. The catalyst structure was characterized by X-ray power diffraction (XRD). The results revealed that the Ni-Cu/GAC has the highest catalytic activity, followed by Cu/GAC and Ni/GAC. Metal oxide loading rate depended on impregnation process, whereas dispersion of metal oxides was controlled by calcination process. The XRD analysis showed that the principal active phase was Cu₂O for Cu/GAC and Ni-Cu/GAC catalyst and NiO for Ni/GAC catalyst. The most active plane was Cu₂O₍₂₀₀₎ and then followed by Cu₂O₍₁₁₀₎ and Cu₂O₍₁₁₁₎ for Cu-supported catalysts. Higher calcination temperature and time favored the generation of Cu₂O but increased the crystalline diameter. It also suggested that promoting the generation of NiO and Cu₂O phase and reducing the crystalline diameter could improve the catalytic activity. During Ni-Cu/GAC preparation, existence of Ni(NO₃)₂ could accelerate the adsorption of Cu(NO₃)₂, promoting the generation of Cu₂O, and improve the dispersion of Cu₂O phase. Graphical Abstract ᅟ

The preparation of rhombic dodecahedral cuprous oxide (rdCu₂O) decorated with various amounts of reduced graphene oxide (rGO) is carried out by using a wet-chemical route. The resultant nanocomposites (denoted as rdCu₂O-xrGO, x = amounts of rGO) possess unique crystal facets of Cu₂O and superior electronic properties of rGO, which are tested as photocatalysts in the degradation of methyl orange (MO) under visible light irradiation. Among all the rdCu₂O-xrGO photocatalysts, the rdCu₂O-1rGO is found to degrade ca. 98% of MO in the presence of very low catalyst concentration (0.0625 g L⁻¹) within 120 min under visible light illumination. This obtained result may be owing to the well interfacial contact of rhombic dodecahedral Cu₂O nanoparticles with high electronic conductivity of rGO sheets that can increase the separation of photo-induced electron-hole pairs, stabilize the Cu₂O, and enhance MO adsorption, which are proofed by using X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, photoluminescence, and UV-Vis diffuse reflection spectroscopy. Most importantly, these efficient photocatalysts can be reusable and retain surpassing photoactivity in terms of MO degradation after cyclic tests, which may provide a possible opportunity for practical applications in purifying wastewater via direct sunlight.

In the present work, an ultrasound-assisted reverse-precipitation method was applied as a new approach for the synthesis of CuₓO/Fe₂O₃/MoC. In the sonication method, a bath type sonicator as a simple, cost-effective, and low intensity sonicator was used. To determine the influence of ultrasonic waves on the morphology and application of nano-hybrid as nano-sorbent, it was also synthesized using the reverse precipitation method. The products were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier transform infrared (FTIR), transmission electron microscopy (TEM), Zeta-potential measurement, and vibrating sample magnetometer (VSM) techniques. The XRD analysis confirmed that the sono-synthesized sample has higher crystallinity than the conventional one and CuO/Cu₂O/MoC/Fe₂O₃ phase was obtained under ultrasound. According to the TEM and FESEM, sono-synthesized nanoparticles were rod-like with a width and length of 3 nm and 40 nm, respectively. Also, a well-dispersed shape and uniform morphology of nanoparticles were obtained using sonication. In comparison with the conventional nano-hybrid, this structure results in more void and accessible sites for adsorption of pollutants. The efficiency of resulting nanoparticles in adsorption of reactive dyes as a model of the pollutant was evaluated by sorption and sono-sorption processes. The sono-synthesized sample removed the pollutants more efficient than the conventional sample. The removal efficiencies were about 99% for the removal of reactive dyes using the sono-synthesized sample and sono-sorption method. Besides, determining factors including pH, pollutant concentration, temperature, and contact time were optimized in the sono-sorption and sorption processes. A colorimetric method based on RGB value was used to determine dye concentration in aqueous media. The images were taken by a smartphone and analyzed by ImageJ software. The accuracy of RGB results was confirmed by a UV–Vis spectrophotometer. Graphical abstract The figures on the left side show the FESEM images of nano-sorbent synthesized in the presence of ultrasonic irradiation (US method) and the absence of it (MS method). A well-dispersed shape and uniform morphology of nanoparticles were obtained using sonication. The scheme on the right side illustrates the process of sono-sorption for the removal of dyes and determination of their concentration using the colorimetric method. A colorimetric method based on RGB value was used to determine dye concentration in aqueous media. The graph shows the removal efficiencies of RY84 onto nanosorbent. The removal efficiencies were about 99% for the removal of reactive dye using the sono-synthesized sample and sono-sorption method

Copper and zinc composite oxides (Cu₂O/ZnO) were synthesized by an impregnation-reduction-air oxidation method. A series of Cu₂O/ZnO/rGO ternary composites were prepared by coupling with graphene oxide (GO) with different mass fractions in a solvothermal reaction system. The microscopic morphology, crystal structure, and optical characteristics of the photocatalysts were characterized. The degradation of p-Nitrophenol (PNP) and polyacrylamide (PAM) by photocatalytic materials under simulated solar irradiation were studied, and the degradation kinetics were also investigated. The results showed that cubic Cu₂O was modified by ZnO nanorods and distributed on rGO nanosheets. The ternary Cu₂O/ZnO/rGO nanocomposites have stronger simulated solar absorption ability and higher photodegradation efficiency than pure ZnO and binary Cu₂O/ZnO nanocomposites. When the amount of Cu₂O/ZnO/rGO-10 was 0.3 g L⁻¹, the degradation rate of 10 mg L⁻¹ PNP reached 98% at 90 min and 99.6% of 100 mg L⁻¹ PAM at 30 min. The photocatalytic degradation processes of PNP and PAM all followed the pseudo-first-order kinetic model. Free radical trapping experiments showed that superoxide radicals were the main active substances to improve photocatalytic efficiency. In addition, after four recycles, the catalytic efficiency of Cu₂O/ZnO/rGO-10 was still over 90%. It showed that Cu₂O/ZnO/rGO-10 was a promising catalyst for wastewater treatment because of its good photostability and reusability.

The simultaneous photocatalytic removal of nitrate from aqueous environment in presence of organic hole scavenger using TiO₂ has long been explored. However, the use of unmodified TiO₂ in such reaction resulted in non-performance or release of significant amount of undesirable reaction products in the process, a problem that triggered surface modification of TiO₂ for enhanced photocatalytic performance. Previous studies focused on decreasing rate of charge carrier recombination and absorption of light in the visible region. Yet, increasing active sites and adsorption capacity by combining TiO₂ with a high surface area adsorbent such as activated carbon (AC) remains unexploited. This study reports the potential of such modification in simultaneous removal of nitrates and oxalic acid in aqueous environment. The adsorptive behaviour of nitrate and oxalic acid on TiO₂ and TiO₂/AC composites were studied. The Langmuir adsorption coefficient for nitrate was four times greater than that of oxalic acid. However, the amount of oxalic acid adsorbed was about 10 times greater than the amount of nitrate taken up. Despite this advantage, the materials did not appear to produce more active photocatalysts for the simultaneous degradation of nitrate and oxalic acid. The photocatalytic activity of TiO₂ and its carbon-based composites was improved by combination with Cu₂O particles. Consequently, 2.5 Cu₂O/TiO₂ exhibited the maximum photocatalytic performance with 57.6 and 99.8% removal of nitrate and oxalic acid, respectively, while selectivity stood at 45.7, 12.4 and 41.9% for NH₄⁺, NO₂⁻ and N₂, respectively. For the carbon based, 2.5 Cu₂O/TiO₂-20AC showed removal of 12.7% nitrate and 80.3% oxalic acid and achieved 21.6, 0 and 78.4% selectivity for NH₄⁺, NO₂⁻ and N₂, respectively. Using the optimal AC loading (20 wt%) resulted in significant decrease in the selectivity for NH₄⁺ with no formation of NO₂⁻, which unveils that selectivity for N₂ and low/no selectivity for undesirable products can be manipulated by controlling the rate of consumption of oxalic acid. In contract, no nitrate reduction was observed with Cu₂O promoted TiO₂-T and its TiO₂-(T)-20AC, which may be connected to amorphous nature of TiO₂-T and perhaps served as charge carrier trapping sites that impeded activity.

Storing and exhibiting cultural heritages are the basic social functions of museum. Since it is impossible to store or display objects without using containers, cases, or holders, the equipment quality is of great importance. Evaluating the suitability of the equipment should not only learn the mechanical behavior but also focus on the materials because some of them (such as woods) may do harm to the objects due to contaminants released. A convenient test by the deposited metal film method has been proposed previously in order to evaluate more potential museum materials in limited time. The conformance between this method and the Oddy test, the classic method for evaluating and selecting museum materials, is mainly studied in this work. The two testing systems were compared from several aspects such as sample appearance, corrosion product, surface morphology, and metallic content by naked eye and modern characterization measures like X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy. The corrosion mechanisms were deduced according to the corrosion products, including Cu → Cu₂O → CuO and Cu → Cu₂O → Cu(OH)₂·H₂O → Cu(HCOO)(OH). The suitability of potential materials for the conservation of metal objects was defined according to the metallic contents of coupons (calculated by atomic ratio) which were classified by the Oddy test. The critical values distinguishing permanently usable from temporarily usable are approximately determined as 70% for copper and 75% for silver, and those distinguishing temporarily usable from unusable are approximately determined as 55% for copper and 60% for silver. The corresponding metal films were classified based on the metallic content standard derived, and then typical appearances of the films assigned to different suitability levels were suggested. Special phenomena, such as the failure in detecting some corrosion products, is attributed to low yield and uneven distribution of ultrafine corrosion products on the films, the covering effect caused by other corrosion products on the copper coupons, and the weakening effect resulted from intensive metal peaks, while some unexpected corrosion conditions on the coupons and the films, are related to the characteristics of general corrosion and pitting corrosion. The results indicate the potential application of the deposited metal film method, giving an optional choice to evaluate and select museum materials with less time. The evaluation methods were preliminarily established from three aspects, such as artificial judgment, metallic content analysis, and corrosion product identification. The artificial judgment is generally applicable, and the other two are useful for verifying the result if possible. More actual cases and further calibration work are essential for further development of the deposited metal film method.