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Emerging contaminants such as pharmaceutical residue brings harmful effects to the environment and human health as well. In Brazil, wastewater treatment plants (WWTPs) for influents and effluents do not remove efficiently that kind of residue due to the conventional biological-like treatment. In this context, alternative treatments, such as electrocoagulation can be used to achieve better removal efficiency based on electrolytic treatment. In this work, electrocoagulation processes (ECOF) were applied to remove antibiotics, such as trimethoprim (TMP) and amoxicillin (AMX) using a direct pulsed current (DPC). The electrocoagulation process was conducted using different anodes (304 and 316L steel electrodes and 1050 aluminum electrodes), and were evaluated experimental parameters such as corrosion rate, pH of the working solution and operational costs. In comparison with other electrodes, the 1050 aluminum electrode showed the larger corrosion rate, longer service life and smaller operational costs (energy and electrode consumptions). In addition, using of the pulsed direct current reduced the consumption energy of the electrocoagulation process by 30% when compared to the same process using direct current. During electrocoagulation process, the electrodes showed a complex hydrolysis equilibrium due to charge density transfer of the electrodes themselves which resulted in an acid-base equilibrium between hydrolysis products and AMX/TMP molecules. For 1050 aluminum electrodes, the pH of the electrolyte during electrocoagulation process changed from 3.0 to 5.5, and the cationic equilibrium containing Al3+ and Al(OH)2+ along the studied molecules was proposed. The same equilibrium approach was used in iron present in the steel electrodes: once the pH ranged from 3.0 to 7.0, the proposed equilibrium for this system evolves Fe3+, Fe(OH)2 and Fe(OH)3 compounds. To investigate the reactivity between AMX/TMP molecules and the electrodic surfaces, DFT calculations were conducted, and the analysis of molecular parameters in the experimental processes showed a passivation effect of AMX and TMP molecules towards 1050 aluminum electrode while AMX presented a corrosion effect in steel electrodes. Therefore, the 1050 aluminum electrode presented the best efficiency over steel electrodes in electrocoagulation process for AMX and TMP removal in wastewater, having potential to be applied in large scale application in a WWTP.

A numerical and experimental study of the multielement adsorption of Cd2+, Cu2+, Ni2+, and Pb2+ metal ions in batch and column system were carried out in aqueous solution using Tururi fibers as adsorbent. The kinetics and thermodynamic equilibrium parameters were studied. The adsorption kinetics was fitted to the homogeneous diffusion model and the results showed good linear correlation coefficients. Furthermore, a mathematical model was built to describe the mass transfer kinetics for fixed bed column tests. The effects of constant adsorption equilibrium, external mass transfer, and intraparticle diffusion resistance on breakthrough curves were studied. The equations which describe the phenomenology were discretized using the finite volumes method with the weight upstream differencing scheme and central difference scheme formulations. The results for the breakthrough curves obtained through simulation showed good agreement compared with the experimental data.

Buriti fibers were subjected to an alkaline pre-treatment and tested as an adsorbent to investigate the adsorption of copper, cadmium, lead and nickel in mono- and multi-element aqueous solutions, the results showed an increase in the adsorption capacity compared to the unmodified Buriti fiber. The effects of pH, adsorbent mass, agitation rate and initial metal ions concentration on the efficiency of the adsorption process were studied using a fractional 24−1 factorial design, and the results showed that all four parameters influenced metal adsorption differently. Fourier transform infrared spectrometry and X-ray fluorescence analysis were used to identify the groups that participated in the adsorption process and suggest its mechanisms and they indicated the probable mechanisms involved in the adsorption process are mainly ion exchange. Kinetic and thermodynamic equilibrium parameters were determined. The adsorption kinetics were adjusted to the homogeneous diffusion model. The adsorption equilibrium was reached in 30 min for Cu2+ and Pb2+, 20 min for Ni2+ and instantaneously for Cd2+. The results showed a significant difference was found in the competitiveness for the adsorption sites. A mathematical model was used to simulate the breakthrough curves in multi-element column adsorption considering the influences of external mass transfer and intraparticle diffusion resistance.

This review discussed the last 10 years progress in the use of lignocellulosic materials chemically modified as low-cost biosorbents. Thus, the chemical modifications, such as chemical pretreatment, oxidation, as well as the grafting of carboxyl groups, amines, amides, etc., on lignocellulosic fibers, that aim to increase the number of adsorption sites and maximize toxic metal ion adsorption capacity have been addressed. The literature presents results that indicated performances of biosorbents equal to or even higher than conventional methods and adsorbents. Many efforts have been concentrated on the improvements of these biosorbents through chemical modifications. However, some difficulties still exist, including the discharge of colored organic compounds resulting from the pretreatments and the development of fast, clean, and low-cost synthesis of selective and multifunctional adsorbents. Thus, the challenge for future research is to find solutions to these difficulties in order to finally make lignocellulosics biosorbents that can replace conventional adsorbent materials. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43286.

The present study aimed at verifying the acid surface modification of dry bean pods subjected to alkaline pretreatment using tannic acid, poly(acrylic acid), and poly(acrylamide-co-acrylic acid) and evaluate their performances as adsorbents in the metal ions removal. Factorial design was used as a tool to study the variables that affects the modification processes. The results showed that there was an increase in the adsorption capacity after acidic changes, mainly for the tannic acid, achieving 45% increasing of removal of all metal ions. The variable pH had negative significant effect in the modification with tannic acid. When the modifying agent was the poly(acrylic acid), the variable initial concentration presented a positive significant effect. That means more poly(acrylic acid) was immobilized in the surface of the bean pod, resulting in higher capacity of adsorption. Temperature was significant variable in the modification with poly(acrylamide-co-acrylic acid), resulting in a strongly negative effect. Analyses of material characterization showed that soluble lipid fraction was removed after the alkaline treatment. Although no morphological changes were observed, there was an improving in the availability of the adsorbents sites after chemical modification. Further, the material exhibited thermal stability up to about 300 °C. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 135, 45879.

The present paper aimed to evaluate the impact of microaeration on both the removal performance of some emerging micropollutants (pharmaceuticals, hormones, and bisphenol A) and the microbial community structure of an anaerobic reactor treating synthetic wastewater. Under anaerobic conditions, the removal efficiencies of the micropollutants were very low (< 10%). However, the microaeration (1.0 mL air·min-1 at 27 °C and 1 atm, equivalent to a QAIR/QINF ratio of 0.1) expressively improved the removal efficiencies of all compounds (> 50%). Therefore, supplementing anaerobic reactors with low amounts of oxygen seems to be an interesting strategy to enhance the removal of the micropollutants tested. However, further studies should be carried out with other compounds in order to evaluate the wide applicability of microaeration to different classes of micropollutants in lab- and full-scale treatment systems. Concerning the microbiota structure, both bacterial and archaeal communities were not compromised by the different operational conditions and preserved their functional organization with high richness during the whole experiment. RESUMO O presente trabalho teve como objetivo avaliar o impacto da microaeração tanto no desempenho de remoção de alguns micropoluentes emergentes (fármacos, hormônios e bisfenol A) quanto na estrutura da comunidade microbiana de um reator anaeróbio tratando uma água residuária sintética. Sob condições anaeróbias, as eficiências de remoção dos micropoluentes foram muito baixas (< 10%). Entretanto, a microaeração (1,0 mL de ar·min-1 a 27 °C e 1 atm, equivalente a uma relação QAR/QAF de 0,1) melhorou expressivamente as eficiências de remoção de todos os compostos (> 50%). Portanto, a suplementação de reatores anaeróbios com baixas quantidades de oxigênio parece ser uma estratégia interessante para melhorar a remoção dos micropoluentes testados. Entretanto, mais estudos devem ser realizados com outros compostos para avaliar a ampla aplicabilidade da microaeração a diferentes classes de micropoluentes em sistemas de tratamento em escala laboratorial e real. Com relação à estrutura da microbiota, tanto as comunidades de bactérias quanto as de arqueias não foram comprometidas pelas diferentes condições operacionais e preservaram sua organização funcional com elevada riqueza durante todo o experimento.