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The growing global concern with water resources management has driven the search for more effective treatments for industrial effluents. The produced water is inserted in this scenario as one of the largest effluents generated by the oil industry. Besides, it cannot be discarded or reused without proper treatment due to its complex and toxic chemical composition. A bibliometric study was performed on the Scopus database from inception to 2020 in order to map the evolution of scientific publications related to the advanced oxidation processes based on reactions with ozone and Fenton's reagent. The results reinforced the efficiency of such processes for treating the produced water and the increasing of publications in the last few years, although the first document appeared only in 1995. China was the leading country in this research area, followed by Brazil and the USA. The most relevant journals were the Environmental Science & Technology and the Journal of Hazardous Materials. The research trends pointed out that the use of Fenton, photo-Fenton, and ozonation processes has been associated with other treatment methods to enhance the removal of contaminants in the produced water samples. However, the documents selected revealed the limitation on these processes due to the high costs with energy consumption. The present study can help other researchers mainly due to the few studies in this area, which demonstrates the importance of this prospection to support the development and application of advanced oxidation processes on produced water treatments. [ABSTRACT FROM AUTHOR]

Hospital laundries are responsible for a significant part of the amount of wastewater that is generated in hospitals. Hospital laundry wastewater represents a complex mixture of chemicals that arouse concerns about possible environmental risks. The objective of the present study was to evaluate the cytotoxicity of different laundry effluents from the Regional University Hospital of Maringá, Paraná, Brazil, on Allium cepa L. meristematic root cells. The effluents were characterised as rinsing, wetting, prewashing, washing, softening, wastewater (the effluent generated at the end of the washing process), the wastewater that was treated by physicochemical (PC) processes and the wastewater that was treated by advanced oxidation processes (PC + UV, PC + H2O2 and PC + UV/H2O2). The mitotic indexes were calculated by scoring 5000 cells per group and the statistical analyses were performed by one-way ANOVA, followed by Tukey's post-test (α = 0.05). Results showed that the rinsing, wetting, prewashing and wastewater laundry effluents were cytotoxic at 24 h of exposure, significantly reducing the mitotic index. Despite the slight cytotoxicity of the PC + UV/H2O2 treatment, physicochemical and advanced oxidation processes efficiently reduced the critical parameters of wastewater, such as the biochemical and chemical oxygen demands, to tolerable levels of effluent discharge. It is essential to perform constant monitoring of these effluents in order to reduce the possible occurrence of environmental impacts. [ABSTRACT FROM AUTHOR]

Sodium percarbonate (SPC, 2Na 2 CO 3 ∙3H 2 O 2), is a compound that can be used under multiple environmental applications. In this work, SPC was employed as oxidant in the treatment of soil contaminated with diesel oil. The soil samples were collected during the earthmoving stage of RNEST Oil Refinery (Petrobras), Brazil. Then, the samples were air-dried, mixed and characterized. Subsequently, raw soil was contaminated with diesel and treated by photo-Fenton reaction (H 2 O 2 /Fe2+/UV). SPC played a significant role in the generation of hydroxyl radicals under the catalytic effect of ferrous ions (Fe2+), hydrogen peroxide (H 2 O 2) and radiation. These radicals provoked the photodegradation of polycyclic aromatic hydrocarbons (PAHs), in the soil remediation. A factorial design 33 was carried out to assess the variables which most influenced the decrease in total organic carbon (TOC). The study was performed with the following variables: initial concentration of [H 2 O 2 and [Fe2+, between 190.0 and 950.0 mmol L−1 and 0.0–14.4 mmol L−1, respectively. UV radiation was supplied from sunlight, blacklight lamps, and system without radiation. All experiments were performed with 5.0 g of contaminated soil in 50.0 mL of solution. The initial concentration of Fe2+ showed the statistically most significant effect. The oxidation efficiency evaluated in the best condition showed a decrease from 34,765 mg kg−1 to 15,801 mg kg−1 in TOC and from 85.750 mg kg−1 to 20.770 mg kg−1 in PAHs content. Moreover, the sums of low and high molecular weight polycyclic aromatic hydrocarbons (LMW-PAHs and HMW-PAHs) were 19.537 mg kg−1 and 1.233 mg kg−1, respectively. Both values are within the limits recommended by the United Sates Environmental Protection Agency (USEPA) and evidenced the satisfactory removal of PAHs from contaminated soil, being an alternative to classic oxidation protocols. Image 1 • Soil collected from refinery area was artificially contaminated with Diesel oil. • Sodium Percarbonate (SPC)-assisted Fenton was highly efficient in PAHs mineralization. • Diesel-contaminated soil was successfully remediated by SPC-assisted Fenton reaction. • The parameters of the treated soil complied with USEPA and Brazilian legislation. [ABSTRACT FROM AUTHOR]

Niobium-based metal oxides are emerging semiconductor materials with barely explored properties for photocatalytic wastewater remediation. Brazil possesses the greatest reserves of niobium worldwide, being a natural resource that is barely exploited. Environmental applications of solar active niobium photocatalysts can provide opportunities in the developing areas of Northeast Brazil, which receives over 22 MJ m2 of natural sunlight irradiation annually. The application of photocatalytic treatment could incentivize water reuse practices in small and mid-sized textile businesses in the region. This work reports the facile synthesis of Nb2O5 catalysts and explores their performance for the treatment of colored azo dye effluents. The high photoactivity of this alternative photocatalyst makes it possible to quickly obtain complete decolorization, in less than 40 min of treatment. The optimal operational conditions are defined as 1.0 g L−1 Nb2O5 loading in slurry, 0.2 M of H2O2, pH 5.0 to treat up to 15 mg L−1 of methyl orange solution. To evaluate reutilization without photocatalytic activity loss, the Nb2O5 was recovered after the experience and reused, showing the same decolorization rate after several cycles. Therefore, Nb2O5 appears to be a promising photocatalytic material with potential applicability in wastewater treatment due to its innocuous character and high stability. [ABSTRACT FROM AUTHOR]

Pulp and paper mill wastewater (PPMWW) contains high concentrations of recalcitrant compounds that cause toxicity to organisms. Advanced oxidation processes (AOPs) have the ability to degrade these compounds and reduce overall toxicity. Physicochemical characterization and Lactuca sativa toxicity test were conducted to compare the effectiveness of two post-treatments: UV/H 2 O 2 and photo-Fenton. A comparison of four phytotoxicity indexes was carried out. PPMWW from a Brazilian treatment plant was characterized by high values of phenols, color, integrated spectral area (ISA), and chemical oxygen demand (COD), and caused significant inhibition to seedling development. The use of both post-treatments allowed the removal of over 75% of phenols, color, ISA, and COD. Although UV/H 2 O 2 was more effective in removing phenols and ISA, photo-Fenton better reduced phytotoxicity. The most sensitive phytotoxicity indexes were RGIC 0.8 and GIC 80% , whereas SGC 0 , REC -0.25 and REC -0.50 better showed the effectiveness of the post-treatments. We suggest the combined use of two phytotoxicity indexes: one that evaluates the effects on seed germination and, another, on root elongation, e.g., SGC 0 and RGIC 0.8 . Additionally, we recommend the use of ISA for monitoring programs of wastewater treatments because it is a cost-effective approach that allows narrowing down the search and identification of compounds present in complex mixtures., (Copyright © 2020 Elsevier Inc. All rights reserved.)