No abstract

Contamination of water by heavy metals is a major environmental concern due to the potential ecological impact on human health and aquatic ecosystems. In this work, we studied the chemical modification of various fruit peels such as banana (BP), granadilla (GP), and orange ones (OP) in order to obtain novel bio-adsorbents to improve the removal of Zn(II) ions from 50 mg·L−1 synthetic aqueous solutions. For this purpose, sodium hydroxide and calcium acetate were employed to modify the fruit peels. The moisture, extractives, lignin, hemicellulose, and cellulose contents of the raw materials were determined according to ASTM standards. The obtained bio-adsorbents were characterized by scanning electron microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR) and thermogravimetric analysis (TGA). The results showed the OP bio-adsorbents performed better, especially when the concentration of the modifier solutions increased, e.g., the OP particles modified using 0.8 M NaOH and Ca(CH3COO)2 solutions resulted in 97% removal of Zn(II) contaminating ions and reached a maximum adsorption capacity of 27.5 mg Zn per gram of bio-adsorbent. The adsorption processes were found to follow a pseudo-second order model. The error function sum of square error indicated the Freundlich isotherm (non-linear regression) as best fit model. The obtained results are particularly interesting for material selection in wastewater treatment technologies based on contaminant adsorption.

The adsorption/degradation of caffeine and irgasan from aqueous artificial solutions by using.Lignocellulosic residues (LR) impregnated with TiO2 nanoparticles was studied. Three different LR were used: bamboo (Guadua angustifolia), laurel (Cordia allidora) and moringa (Moringa oleifera Lam.), each one with three nominal particle size ranges: 75–149, 45–75, and ≤45 μm. Commercially available TiO2 nanoparticles were added to these residues using the wet impregnation technique. The chemical composition of the LR was determined according to ASTM standards. FTIR spectroscopy and scanning electron microscopy were used to determine the functional groups and morphology of the modified materials, respectively. Adsorption/degradation tests were carried out in batch systems as a function of adsorbent concentration, contact time, nanoparticle content on the impregnated residues and light type influence. The maximum adsorption capacity was (37.1 mg. g-1/55.3 mg.g-1), using 40 wt.% nanoparticle-impregnated ≤45 μm laurel residues during 180 minutes, for a (7.0/0.7 g.L-1) concentration of (caffeine/irgasan). The caffeine adsorption isotherms were well described by the Langmuir and Freundlich models, while the Freundlich model describes irgasan adsorption. The use of UV radiation accelerated threefold the removal process.

Plastic waste generated by the Ecuadorian agro-industrial sector represents one of the main environmental impacts, particularly in floricultural and banana production, as a result of its use as a greenhouse cover and as a protective element for the fruit cluster, respectively. The situation become more complicated because of the level of degradation caused by environmental exposure and the degree of contamination due to the use of agrochemicals that plastics present once their useful life has expired. The current research was divided into two stages: characterization of plastic waste and conditioning prior to reprocessing. The results revealed the plastic waste of the floricultural and banana sector, whose predominant material corresponds to LDPE and HDPE, respectively, presents a level of contamination that allows them to be considered as “non-hazardous” waste, which allows them to be recycled, but their processes must be properly controlled and carried out by qualified people. The level of degradation in the exposed banana bags showed losses of mechanical properties of tensile less than 50%, which means that the material is not degraded and it is feasible to recycle it directly. Additionally, the FTIR-ATR spectra on both sides of the film in the samples did not register representative bands of oxidation. On the other hand, in the greenhouse waste, the losses of mechanical properties of tensile strength above 50% as well as the noticeable formation of carbonyl groups in the structure of the material showed the degradation of the plastic. Therefore, the feasibility of recycling will depend on the incorporation of virgin material. The conditioning of the waste for subsequent recycling revealed the need of a washing process consisting of four stages: initial cleaning, pre-wash, washing, and air-drying.

Water bodies and aquatic ecosystems are threatened by discharges of industrial waters. Ecotoxicological effects of components occurring in untreated and treated wastewaters are often not considered. The use of a linear, multi-compartmented, non-forced, static system constructed with PET bottles is proposed for the quality assessment of treated waters, to deal with such limitations. Two synthetic waters, one simulating wastewater from the textile industry and the other one simulating wastewater from the cassava starch industry, were prepared and treated by homogeneous Fenton process and heterogeneous photocatalysis, respectively. Untreated and treated synthetic waters and their dilutions were placed into compartments of the non-forced exposure system, in which zebrafish (Danio rerio), the indicator organism, could select the environment of its preference. Basic physical–chemical and chemical parameters of untreated and treated synthetic waters were measured. The preference and avoidance responses allowed verification of whether or not the quality of the water was improved due to the treatment. The results of these assays can be a complement to conventional parameters of water quality.

El objetivo del estudio fue evaluar la eficiencia de una laguna de estabilización aerobia piloto anexa al tratamiento primario existente para los lixiviados producidos en un botadero controlado ubicado en la Provincia de Pichincha-Ecuador. Se caracterizó el lixiviado a la entrada y salida del sistema cada 14 días por un tiempo de retención de 51 días por dos periodos. El lixiviado que alimento la laguna alcanzó una concentración máxima de DBO5 de 722 mg L-1 y DQO de 1338 mg L-1. Luego del tratamiento, el lixiviado redujo la DBO5 a 9 mg L-1 y DQO a 91 mg L-1 para el primer periodo de muestreo y 62 mg L-1 de DBO5 y 294 mg L-1 de DQO para el segundo periodo, es decir, una eficiencia de remoción en función de DQO fue del 91,17% y 98,24% de DBO5. Además, la remoción de coliformes fecales fue de 99,99%. Adicionalmente, se examinaron varios parámetros físico-químicos para analizar el aporte a la calidad del lixiviado. Con los datos de concentración de materia orgánica y aforo del lixiviado se determinó los parámetros de diseño del tratamiento biológico anexo al tratamiento primario existente.

The production of plastic materials in 2016 was approximately 280 million tons, of which about 75% were disposed of in landfills. The constant accumulation of this type of waste has caused negative impacts on flora and fauna due to its low biodegradability. As an alternative to this complex problem, this work proposes the formulation of biopolymer mixtures based on polylactic acid (PLA) and native starch, as a viable option to minimize the impact caused by conventional plastics.

The search for inexpensive and environmentally friendly alternatives for used motor oil (UMO) purification has become a topic of research. In this study, the use of bentonite clay modified by acid activation is proposed. Sulfuric acid, acetic acid (v-acid/w-clay ratio=20, 40 and 60%) and sulfuric/acetic mixtures (1:1 ratio) were used in the bentonite clay activation. The activated clays were used in the UMO treatment in a ratio of 1:4 w/v, using batch adsorption processes (contact time=12 min). To determine the structural and morphological modifications produced by the acid activation process, the clays were characterized by Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy. The oil clarification efficiency was quantified by UV-Vis spectroscopy, acidity, alkalinity and viscosity index. It was determined that sulfuric acid and the sulfuric/acetic activations presented a similar bentonite structure transformation, which appears in the cations leaching of intermediate layer. The treated oil with the highest clarifications (with respect to UMO) were the ones treated using bentonite activated with sulfuric acid 40 v/w% and sulfuric/acetic acid (1:1 ratio) with clarifications of 70 and 68%, respectively. The oil treated with clay activated with sulfuric acid (40%) reduced its viscosity, acidity and alkalinity by 23%, 80% and 29%, respectively.