O efeito de dois diferentes anodos metálicos na eletrocoagulação de efluentes oleosos sintéticos

In the present work, electrocoagulation process (EC) aluminum and iron were comparing as materials for anode and stainless steel as cathode, under different operational parameters, such as: initial concentration of oil, area-volume relation (SA/V), pH, electrodes geometry, current density and sludge production. Chemical oxygen demand (COD) and turbidity removals were selected as performance criteria. The current density, SA/V and electrode geometry were found to be the most significant parameters. The results have shown that electrocoagulation, using both kind of anodes materials (Fe/Al), successfully removes the COD and turbidity in experimental conditions such as: the current density, 9.4 mA/cm2, distance between electrodes, 10 mm; SA/V, 30.35 m2/m3 and 30 minutes of operation. Removal efficiencies over 99% and 98% were measured for COD and turbidity, using anodes of aluminum. Likewise 94.8% of COD and 98.5% of turbidity were removed from synthetic wastewater, using anode of iron. The sludge produced after electrocoagulation treatment was 2.2 kg/m3 for aluminum and 2.76 kg/m3 for iron. Key words: electrocoagulation, emulsions, wastewaters.No presente trabalho, foi avaliado o processo de eletrocoagulação (EC), comparando eletrodos de alumínio e ferro como material de anodo e aço inoxidável como material de catodo, operando com diferentes parâmetros tais como: concentração inicial do óleo, relação área-volume (SA/V), pH, geometria dos eletrodos, densidade de corrente e produção de lodos. A redução da demanda química de oxigênio (DQO) e turbidez foram às variáveis respostas analisadas. A densidade de corrente, SA/V, e geometria dos eletrodos foram os parâmetros com maior influência no processo. Os resultados mostraram que a eletrocoagulação, para os dois tipos de materiais de anodos (Fe/Al), conseguem uma excelente redução da DQO e da turbidez nas seguintes condições experimentais: densidade de corrente: 9,4 mA/cm2, distanciamento entre os eletrodos, 10 mm, SA/V, 30,35 m2/m3 e 30 minutos de operação. Eficiências de redução de 99% e 98% foram alcançadas para a DQO e a turbidez com anodos de alumínio. Do mesmo modo 94,8% da DQO e 98,5% da turbidez para o caso do ferro foi reduzido do efluente sintético. A borra produzida foi de 2,2 kg/m3 para alumínio e 2,76 kg/m3 para o ferro. Palavras-chave: eletrocoagulação, emulsões, águas residuais

Scientometric study of treatment technologies of soil pollution: present and future challenges

There are few bibliometric studies showing current technologies and their combinations for the remediation of contaminated soils. For this reason, a scientometric study was carried out in order to know the trends in soil contamination treatment technologies. The study considered original articles and reviews published in the Scopus and Web of Science databases between January 2010 and June 2021, evaluating: (a) characteristics of the publications, (b) main research sources, (c) citations and production by journals, (d) keywords used, (e) countries, institutions and authors active in research production, (f) most cited articles and (g) trends in soil treatment and remediation techniques. The results showed: (a) continuous growth of publications on soil remediation in the “Environmental Science” subject area and a limited contribution of the “Soil Science” and “Agriculture and Biological Science” subject areas, (b) leadership of countries such as China, USA, India, Italy and Spain in research production, (c) phytoremediation, bioremediation and biodegradation were the most studied treatment technologies in the last decade and (d) recent research (from 2020) studied pesticides and herbicides, including Chlorimuron-ethyl and also microplastics and other emerging pollutants. It is also noted that the current trend of combinations of techniques for the treatment of soil contamination is attractive for future research.Campus San Juan de Luriganch

Cinética de descontaminación de aguas de curtiembre utilizando biofloculantes

En esta investigación se evaluó la cinética de reducción de la turbidez inicial (1455 UNT) de aguas residuales de una industria curtiembre mediante la aplicación de biofloculantes directos elaborados a partir del alga Chondracanthus chamissoi (alginato) y de las mudas del crustáceo Emerita analoga (quitosano). Se recolecto el material biológico precursor en las playas de Lima, Perú, a partir de este material; se produjo ácido algínico fibroso y posteriormente alginato de sodio. Se usaron los procesos de desmineralización, desproteinización y posterior desacetilación para obtener el quitosano a partir de las mudas del crustáceo. Se evaluó el efecto del pH, la dosis de los biofloculantes, el tiempo de equilibrio del proceso. Además, se determinó el orden cinético de la velocidad de floculación mediante la prueba de jarras. Los resultados indicaron una remoción de la turbidez superior al 99 % dentro de los primeros 30 minutos para dosis de 0.2 a 2 g/l de floculantes y pH ácido (igual a 4); no se registraron diferencias significativas a distintos valores de pH (4-12) y dosis (0.2 a 2 g/l). El ajuste lineal entre el tiempo de floculación y la turbidez generó ecuaciones cinéticas significativas de primer orden para ambos floculantes con constantes de velocidad k1 del orden de 10-4 (1/NUT.min) y tiempos de reducción de la mitad de material particulado (vida media: τ1/2) inferiores a los 10 minutos. Esto se puede considerar como un criterio para medir la eficiencia del proceso de floculación directa en el tratamiento de aguas industriales de curtiembre.Campus San Juan de Luriganch

[pt] ELETROFLOTAÇÃO DE FINOS DE CASSITERITA E QUARTZO UTILIZANDO A CEPA RHODOCOCCUS OPACUS COMO BIORREAGENTE

Neste trabalho foi realizado o estudou da eletroflotação de finos de cassiterita e quartzo, utilizando o microrganismo Rhodococcus opacus como biorreagente. Os ensaios de eletroflotação foram realizados em tubo de Hallimond modificado, usando aço inox como cátodo e uma tela de Ti/RuO2 como ânodo. As características da superfície do microrganismo e os possíveis mecanismos de interação envolvidos na bioadesão foram avaliados com base em medições de potencial zeta, análises por espectrometria no infravermelho e análises de micrografias obtidas no microscópio eletrônico de varredura (MEV). Após a interação foi observado um caráter hidrofóbico nas partículas de ambos os minerais, e verificado pelas medidas de ângulo de contato. Através de ensaios de adesão foi observada uma maior afinidade do microrganismo pela cassiterita. Estes ensaios também indicaram o pH da solução como o parâmetro de maior influencia, sendo que, maiores quantidades de bactéria aderida foram obtida em valores de pH em torno de 3,0; com 5 min de interação. O tamanho médio da bolha Sauter, obtido pelo método de difração laser, foi de 26 micrometros, usando 50 mg/L de microrganismo e 51,4 mA/cm2 de densidade de corrente. A densidade de corrente e concentração de bactérias mostraram-se os parâmetros de maior influencia no tamanho das bolhas. Assim, bolhas de tamanho menor foram obtidas quando os valores destes parâmetros foram incrementados. A melhor flotabilidade para a cassiterita foi observada em pH 5,0, sendo 64.5 por cento com uma concentração de bactérias de 50 mg/L. Para o quartzo a porcentagem foi em torno de 30 por cento em toda a faixa de pH e concentração da bactéria. Os ensaios de microflotação mostraram que R. opacus contribuiu para uma elevada flotação da cassiterita e uma limitada flotação do quartzo. Ensaios de flotabilidade para uma mistura sintética de cassiterita-quartzo (1:1) foram também realizados, sendo obtidas recuperações médias de cassiterita de 67,8 por cento com um teor no concentrado de 64,4 por cento, partindo de um teor de alimentação igual a 42,9 por cento de SnO2.In this work, the electroflotation of quartz and cassiterite fine was carried out using Rhodococcus opacus as bioreagent. The electroflotation cell was Hallimond tube modified, with stainless steel as cathode and Ti/RuO2 mesh as anode. The characteristics of the microorganism surface and the corresponding interaction mechanisms in the bioadhesion were evaluated based on the zeta potential, infrared spectroscopy, scanning electron microscopy and contact angle measurements. After the interaction the resulting particles exhibited hydrophobic character, as verified by the increase of the contact angle. The results, also, showed that the microorganism has a higher affinity for cassiterite particles. It was observed a strong influence of pH on adhesion. The higher adhesion values were obtained around pH 3 and the time required to reach equilibrium was 5 min for both minerals. Current density and bacterial concentration seem to be the main parameters affecting the mean diameter of bubbles. Fine bubbles were obtained when the values of these parameters increased. The mean bubble size obtained (Sauter) by the laser diffraction method was 26 micrometers with an organism concentration of 50 mg/L and current density of 51.4 mA/cm2. The best flotability of cassiterite (64.5 per cent) was observed at pH 5.0 with a R. opacus concentration of 50 mg/L. For quartz the maximum flotability achieved was 30 per cent throughout the all pH range and bacteria concentration tested. It is shown through microflotation tests that R. opacus is able to float cassiterite very well and quartz limitedly. Also, the flotability of cassiterite was evaluated in tests by using a synthetic mineral mixture. An average recovery of 67.8 per cent of cassiterite was obtained with a concentrated grade of 64.4 per cent, starting from 42,9 per cent in the feed grade (SnO2)

Chemical Characteristics and Identification of PM10 Sources in Two Lima Districts, Peru

This study evaluates the concentration of PM10 and PM2.5 and identification of source in the districts of San Juan de Lurigancho and Puente Piedra (PPD) in Lima-Peru. The samples were collected from April to May 2017 by the National Meteorology and Hydrology Service of Peru (Senamhi). The concentration of PM10 and PM2.5, measured by gravimetric techniques, exceeded the international (WHO) and national standards; with maximum values for PM10 and PM2.5 of 160 and 121.56 µg/ m3 in PPD and 295.06 and 154.58 µg/ m3 in SJL. Identification of sources by the Positive Matrix Factorization Model (PMF 5.0) and Principal Component Analysis (ACP), showed similar sources for both districts. In SJL, the combination of vehicular traffic and resuspension of soil dust, marine aerosol and iron and steel industry was determined, while in PPD the resuspension of soil dust, vehicular source, industrial activity and marine aerosol.El presente estudio evalúa la concentración de PM10 y PM2.5 e identifica las fuentes contaminantes en los distritos de San Juan de Lurigancho (SJL) y Puente Piedra (PPD), Lima-Perú. Las muestras fueron colectadas por el servicio nacional de Meteorología e Hidrología del Perú en Abril a mayo del 2017. La concentración de PM10 y PM2.5, registradas a través de técnicas gravimétricas, excedieron el estándar internacional (OMS) y nacional; encontrándose valores máximos para PM10 y PM2.5 de 160 y 121.56 µg/ m3 en PPD y 295.06 y 154.58 µg/ m3 en SJL. La identificación de fuentes contaminantes para PM10 y PM2.5, obtenidas mediante el Modelo de Factorización de Matriz Positiva (PMF v. 5.0) y análisis por componentes principales (ACP), mostraron fuentes similares para ambos. En SJL se determinó la combinación de tráfico vehicular + resuspensión de polvo de suelo, aerosol marino e industria de hierro y acero; mientras que, en PPD se logró identificar la resuspensión de polvo del suelo, fuente vehicular, actividad industrial y aerosol marino

Chemical characteristics and identification of PM10 sources in two districts of Lima, Peru

This study evaluates the concentration of PM10 and PM2.5 andidentifies the sources of pollution in the districts of San Juan de Lurigancho (SJL) and Puente Piedra (PPD) located in the eastern and northern zones of the Metropolitan area of Lima,Peru. The samples were collected between April and May 2017 by the National Meteorology and Hydrology Service of Peru (SENAMHI). The concentrations of PM10 and PM2.5, measured using gravimetric techniques, exceeded the international (WHO) and national reference values; with maximum values for PM10 and PM2.5 of 160 and 121.56 µg/ m3 in PPD and 295.06 and 154.58 µg/ m3 in SJL respectively. Pollution sources were identified using the Positive Matrix Factorization Model (PMF 5.0) and Principal Component Analysis (PCA), and showed similar sources for both districts. In SJL, sources were determined to be a combination of vehicular traffic and the resuspension of soil dust, marine aerosols and iron and steel industry by-products, while in PPD they consisted of the resuspension of soil dust, vehicular traffic, industrial activity and marine aerosols