No abstract

No abstract

Tannery wastewater contains large quantities of organic and inorganic compounds, including toxic substances such as sulfides and chromium salts. The evaluation of wastewater quality in Chile nowadays is based on chemical specific measurements and toxicity tests. The goal of this research was to characterize tannery wastewater and to relate its physical/chemical parameters with its acute toxicity effect on Daphnia pulex. To distinguish the most important toxic compounds, physical/chemical techniques were applied to a grab sample of a final effluent based on the Phase I toxicity identification evaluation (TIE) procedure. In addition, the toxicity of a beamhouse effluent after an activated sludge reactor treatment was investigated on Daphnia magna (introduced species) and D. pulex (native species). Effluent from different tannery processes (soaking, beamhouse, tanning and final) demonstrated high values of chemical organic demand (COD; 2840-27,600 mg L(-1)), chloride (1813-16,500 mg L(-1)), sulfate (230-35,200 mg L(-1)), and total solids (8600-87,100 mg L(-1)). All effluents showed extremely toxic effects on D. pulex, with 24-h mean lethal values (LC(50)) ranging from 0.36% to 3.61%. The Phase I TIE profile showed that toxicity was significantly reduced by air stripping, filtration, and a cationic exchange resin, with toxicity reductions ranging between 46% and 76%. The aerobically treated beamhouse effluent showed significantly less toxicity for both species (43%-74%). The chemical parameters demonstrated that the remaining toxicity of the treated beamhouse effluent was associated with its ammonia (120 mg N-NH(3) L(-1)) and chloride (11,300 mg Cl(-) L(-1)) contents.

The mining industry is the major producer of acid mine drainage (AMD). The problem of AMD concerns at active and abandoned mine sites. Acid mine drainage needs to be treated since it can contaminate surface water. Constructed wetlands (CW), a passive treatment technology, combines naturally-occurring biogeochemical, geochemical, and physical processes. This technology can be used for the long-term remediation of AMD. The challenge is to overcome some factors, for instance, chemical characteristics of AMD such a high acidity and toxic metals concentrations, to achieve efficient CW systems. Design criteria, conformational arrangements, and careful selection of each component must be considered to achieve the treatment. The main objective of this review is to summarize the current advances, applications, and the prevalent difficulties and opportunities to apply the CW technology for AMD treatment. According to the cited literature, sub-surface CW (SS-CW) systems are suggested for an efficient AMD treatment. The synergistic interactions between CW components determine heavy metal removal from water solution. The microorganism-plant interaction is considered the most important since it implies symbiosis mechanisms for heavy metal removal and tolerance. In addition, formation of litter and biofilm layers contributes to heavy metal removal by adsorption mechanisms. The addition of organic amendments to the substrate material and AMD bacterial consortium inoculation are some of the strategies to improve heavy metal removal. Adequate experimental design from laboratory to full scale systems need to be used to optimize equilibria between CW components selection and construction and operational costs. The principal limitations for CW treating AMD is the toxicity effect that heavy metals produce on CW plants and microorganisms. However, these aspects can be solved partially by choosing carefully constructed wetlands components suitable for the AMD characteristics. From the economic point of view, a variety of factors affects the cost of constructed wetlands, such as: detention time, treatment goals, media type, pretreatment type, number of cells, source, and availability of gravel media, and land requirements, among others.

The green synthesis of nanoparticles allows for obtaining nanomaterials using plant extracts, avoiding the use of toxic and dangerous chemical compounds. The aim of this study was to evaluate the effect of phenolic compounds in plant extracts on the synthesis of iron oxide nanoparticles (Fe x O y -NPs) with photocatalytic activity. Accordingly, the phenolic content in 11 plant extracts was evaluated by the Folin-Ciocalteu (F-C) method, and the iron-reducing capacity was evaluated by the ferric-reducing antioxidant power method (FRAP). From the F-C and FRAP analyses, the Luma apiculata (LAL), Phragmites australis (PAL) and Eucalyptus globulus (EGL) extracts were selected and analyzed by HPLC coupled with a diode array detector (DAD) to identify and quantify the phenolic compounds. Using the three selected extracts, Fe x O y -NPs were synthesized, which were then characterized by UV-Vis spectroscopy, FTIR, DLS, zeta potential, SEM-EDX, and Raman and diffuse reflectance spectroscopy. The SEM-EDX, DLS and zeta potential analyses showed that the Fe x O y -NPs were spherical, stable and nanosized. The FRAP, F-C and FTIR analyses indicated the role of phenolic compounds in the formation and stabilization of Fe x O y -NPs. It was possible to establish a direct relationship between the composition of the phenolic compounds and the reducing capacity of the extracts. In addition, it was found that phenolic compounds and their concentrations are associated with the size and type of Fe x O y -NPs obtained. Furthermore, it was proposed that types of phenolic compounds influence the formation of different phases of Fe x O y -NPs. The photocatalytic activity of the Fe x O y -NPs was demonstrated by diffuse reflectance spectroscopy and decolorization of a dye under visible radiation.

No abstract

No abstract

No abstract