RESUMO
Beauty salons (BS) are places that deal with a wide range of cosmetics with potentially hazardous chemicals, and their effluent should be properly treated before going to the sewage system, once it represents characteristics of industrial wastewater. This work provides an extensive characterization of a BS effluent and its respective electrochemical treatment by comparing NaCl, Na2SO4, and Na2S2O8 as supporting electrolytes with a boron-doped diamond (BDD) as anode, applying 10 or 30 mA cm-2 of current density (j). The inclusion of UVC irradiation was also performed but the improvements achieved in removing the organic matter were null or lower. The analysis of chemical oxygen demand (COD) removal, energy consumption, and total current efficiency (TCE) was required to prove the efficacy of the processes and the comparative study of the performance of different technologies. Precipitate analysis was also done due to the high turbidity of the raw effluent and the appearance of a precipitate before and during the electrolysis, mainly with Na2S2O8. The precipitate confirmed the presence of silicates and small amounts of heavy metals. The results clearly showed that 6 h of treatment with Na2SO4 achieved 58% of COD removal with an energy consumption of about 0.52 kWh m-3, being the best electrolyte option for treating BS effluent by applying 10 mA cm-2. Under these experimental conditions, the final wastewater can be directly discharged into the sewage system with a lower amount of visible precipitate, and with 73% less turbidity. The treatment here proposed can be used as an alternative to decision-makers and governments once it can be a step further in the implementation of better and advanced politics of water sanitation.
Assuntos
Águas Residuárias , Poluentes Químicos da Água , Oxirredução , Esgotos , Sulfatos/análise , Poluentes Químicos da Água/análise , Eletrólitos , Diamante/química , EletrodosRESUMO
A mild, practical, and environmentally friendly method for the hydrodecarboxylation of fatty acids using an acridine-based photoredox catalyst and thiophenol was developed. Cn-1 alkanes were synthesized in good to excellent yields (up to 99 %) from C10-C18 saturated fatty acids under visible light irradiation (405â nm). The developed protocol was employed for a mixture of fatty acids obtained from the hydrolysis of Licuri oil, affording a mixture of C9-C17 hydrocarbons in quantitative yield, which demonstrates the potential application of the method to produce drop-in biofuels.
RESUMO
The traditional transition metal-catalyzed cross-coupling reaction, although well suited for C(sp2)-C(sp2) cross-coupling, has proven less amenable toward coupling of C(sp3)-hybridized centers, particularly using functional group tolerant reagents and reaction conditions. The development of photoredox/Ni dual catalytic methods for cross-coupling has opened new vistas for the construction of carbon-carbon bonds at C(sp3)-hybridized centers. In this chapter, a general outline of the features of such processes is detailed.
RESUMO
A new method for the electrophilic α-alkynylation of ketones was developed using hypervalent iodine under mild and metal-free conditions. Carbonyl compounds containing an α-acetylene group were obtained in good to excellent yields for several ketones using 1-[(trimethylsilyl)ethynyl]-1,2-benziodoxol-3(1H)-one (TMS-EBX) as an alkynylation agent in the presence of t-BuOK and TBAF in THF as solvent. Under the same conditions, an aldehyde was alkynylated.
RESUMO
The aqueous tin-mediated Barbier reaction affords good to excellent yields and moderate syn diastereoselectivity under basic and acidic conditions. The high yields and stereoselectivity observed in the case of o-substituted aldehydes suggest a cyclic organotin intermediate or transition state in K2HPO4 solution. A practical and efficient aqueous tin allylation of methoxy- and hydroxybenzaldehydes can be carried out in HCl solution in 15 minutes to afford the corresponding homoallylic alcohols in high yields. Aliphatic aldehydes give moderate to excellent yields with reaction times ranging from 30 to 60 minutes. Under these conditions, crotylation gives exclusively the gamma-product and the syn isomer is formed preferentially. For 2-methoxybenzaldehyde, an equilibration of the isomers to a syn/anti ratio of 1:1 can be observed after several hours. Control experiments with radical sources or scavengers give no support for radical intermediates. NMR studies suggest a mechanism involving an organotin intermediate. The major organotin species formed depends on the reaction medium and the reaction time. The use of acidic solution reduces the reaction times, due to the acceleration of the formation of the allyltin(IV) species.