A sustained approach to environmental catalysis: Reutilization of chromium from wastewater

Wastewater pollution with heavy metals is an issue of great environmental concern. The future development of clean technologies for the treatment of wastewater loaded with heavy metals entails environment friendly and sustainable processes that may allow simultaneously the recovery of the metals and their reutilization as value-added catalysts to be used in environmental applications. This is the first review regarding the biorecovery of metals and their further reutilization as heterogeneous catalysts. In this regard, metallic residues that generally would be considered as a waste at the end of the treatment process can be reutilized and transformed into value-added catalysts to be used in environmental applications. This review is focused in two broad areas: the biorecovery of chromium by a combined biosorption system consisting of bacteria supported on zeolites, and the catalytic reutilization of the metal-loaded zeolites in the oxidation of organic compounds, both in gaseous and liquid phase. After an overview describing the main subjects in the field of heavy metals recovery, biosorption, zeolites and catalytic oxidation, in the following sections special emphasis will be given to the main results and findings regarding these clean technologies of biorecovery and reuse of metals in catalytic reactions of environmental concern.B. Silva is thankful for the Project “BioEnv—Biotechnology and Bioengineering for a sustainable world,” REF. NORTE-07-0124-FEDER-000048, cofunded by the Programa Operacional Regional do Norte (ON.2 – O Novo Norte), QREN, FEDER. The authors are grateful to FCT and FEDER (European Fund for Regional Development)-COMPETE-QREN-EU for financial support to the Research Centres, PEst-OE/EQB/LA0023/2013, and PEst-C/QUI/UI0686/2013 (F-COMP-01-0124-FEDER-037302)

Catalytic reutilization of Cr(VI) biosorption supports

This work reports the application of a biosorbent, Arthrobacter viscosus, to a zeolitic support (FAU zeolites) as a method for the treatment of Cr(VI)-containing solutions that allows the recovery of the Cr-laden supports as catalysts for liquid-phase oxidation reactions

Degradation of textile dyes in aqueous solutions using type-Fenton bimetallic zeolite catalysts

[Excerpt] Textile dyes are growing to be a problematic class of pollutants to the environment. The disposal of dyes in water resources has bad aesthetic and health effects, since most of them are carcinogenic and mutagenic [1,2], so it is important to remove them from the environment. Effective and economic treatment by advanced oxidation processes (AOPs) has been attracted great and continuous interest for the degradation of these pollutants [3]. [...]This work has been developed under the scope of the projects: BioTecNorte (operation NORTE-01-0145-FEDER-000004), PTDC/AAGTEC/5269/2014, and Centre of Chemistry (UID/QUI/00686/2013 and UID/QUI/0686/2016).info:eu-repo/semantics/publishedVersio

Novel environmental catalysts prepared with residual metals on bioactive nanomaterials

Volatile organic compounds (VOCs), which are emitted from many industrial processes and transport activities, constitute an important concern for the scientific community due to their role in atmospheric pollution and subsequent impact on human health. Among the various methods that can be applied to efficiently control VOCs emissions, catalytic oxidation over solid catalysts seems to be the most efficient and cost-effective technology. Catalysts used for the treatment of gas streams contaminated with VOCs are mostly based on noble metals. Using low cost transition metals such as chromium to replace the noble metal in the catalysts is quite desirable in terms of economical and practical consideration. The catalytic oxidation of 1,2-dichlorobenzene was investigated over NaY and NaX zeolites, loaded with chromium through the action of a robust biosorption system consisting of a bacterial biofilm supported on the zeolites. The results of biosorption showed that the maximum metal removal efficiency was 20%, in both systems based on NaYor NaX, starting from solutions with chromium(VI) concentrations ranging from 50 to 250 mgCr/L [1]. The bacterial biofilm, Arthrobacter viscosus, supported on the zeolite reduces Cr(VI) to Cr(III). The Cr(III) is retained in the zeolite by ion exchange. The new catalysts were characterized by spectroscopic methods (FTIR and ICP-AES), surface analysis (XRD) and thermal analysis (TGA). These catalysts, Cr/FAU, prepared through this new procedure present good activity and selectivity for 1,2-dichlorobenzene oxidation in wet air at 350oC. The study was extended to the oxidation of ethyl acetate and to the oxidation of ethanol [2]

Comparative study between natural and artificial zeolites as supports for biosorption systems

This study aims the definition of a new material that may act as a robust and yet cost effective biosorbent for treatment of wastewater with low concentration of heavy metals. A comparative study was made between two biosorption systems composed of an Arthrobacter viscosus biofilm supported on Cuban natural zeolites and on prepared NaY and NaX, in terms of their ability to retain ionic chromium. The bacterium is able to reduce Cr(VI) to Cr(III) and, only then, this smaller and positive ion may be entrapped in the zeolite cages by ion exchange. The first support was tested in a continuous flow semipacked bed column. The highest removal ratio, 42%, was achieved for initial chromium concentration of 10 mg/L, but the best up-take, 5.5 mg/gzeolite, was obtained for initial concentration of 70 mg/L. Biosorbents prepared with the same biofilm supported in NaY and NaX zeolites were also considered in batch studies, with a typical kinetics of biosorption processes, reaching 20% of initial chromium removal within an initial range of Cr(VI) concentration between 50 and 250 mg/L. These last structures were characterized by spectroscopic methods (FTIR and ICP-AES), surface analysis (DRX) and thermal analysis (TGA). All these techniques indicated that the biosorption process does not modify the morphology and structure of the FAU-zeolites.Departamento de Ciências da Terra da Universidade do Minho; La Habana University; Fundação para a Ciência e Tecnologia, Ministério da Ciência e Tecnologia, Portugal; FEDER

Fenton-type heterogeneous catalysts based in zeolites for water treatment

Water pollution is one of the most important environmental problems in the world. Large amounts of synthetic organic contaminants are released daily into different types of wastewaters and ultimately enter into natural water bodies. It is well known the vast majority of these compounds are persistent organic pollutants, owing to their high stability to sunlight irradiation and resistance to microbial attack. Advanced oxidation processes (AOPs) have been demonstrated to achieve good results for the elimination of organic pollutants from wastewater with very short treatment times. Fenton-type heterogeneous processes have received much attention for their low cost, high efficiency, and moderate conditions among these AOPs.1 In heterogeneous Fenton-type catalysis, iron (or other transition metals) is stabilized on/in the catalysts structure and thus can reduce hydroxide precipitation over a wider pH range.2 This work report the preparation of bimetallic heterogeneous catalysts based in NaY zeolite with Fe, Cu and Mn by ion-exchange method using different routes (Figure 1). Different characterization techniques show that the metals are cationic and show higher oxidation efficiency against the azo dyes, tartrazine and procion yellow, and the order of metal ion exchanging are important to improve their catalytic activity. The prepared bimetallic catalysts can be used at least three times without a significant loss of catalytic activity, proving to have a very high stability.We thank the Fundação para a Ciência e Tecnologia for financial support through Centre of Chemistry (UID/QUI/00686/2013 and UID/QUI/0686/2016) and BioTecNorte (operation NORTE-01-0145-FEDER-000004), and the INAGBE (Instituto Nacional de Gestão de Bolsas de Estudo, Angola) for the PhD grant of BLCS.info:eu-repo/semantics/publishedVersio

Science image in Portugal: studying high school students

In the development of activities for the dissemination of science and scientific work there are difficulties and challenges. People get in touch with science in different contexts, as in their workplace or their social life. However, it is in school that the largest number of interaction activities occurs, through communication and education practices. And high school is probably a key context to the promotion of science among young people. We have conducted an exploratory study on the image of science within Portuguese high school students, in order to collect useful data for communicating and attracting them to higher education. For this purpose, we have gathered a research team that includes two researchers of Basic Sciences (responsible for bringing to the project their vision and experience on science communication activities over the years) and two researchers of Communication Sciences (in charge of designing the study and its conceptual framework). This interdisciplinary team has been crossing experiences and knowledges gathered from their contact with communication science practices and their research in strategic communication. Within this context, we have developed a pilot survey that analyses the image of science and scientists hold by high school students within University of Minho’s area of influence (north of Portugal).(undefined

Bioremoval of hexavalent chromium by A. viscosus supported on Y and ZSM5 zeolites

Este resumo faz parte de: Book of abstracts of the Meeting of the Institute for Biotechnology and Bioengineering, 2, Braga, Portugal, 2010. A versão completa do livro de atas está disponível em: http://hdl.handle.net/1822/1096

Effect of concentration of the diazoalcene molybdenum complex immobilized in ureasil matrix

The complex trans-[FMo(NNCHCHCHCH2CH3)(Ph2PCH2CH2PPh2)2][BPh4], was dispersed in a hybrid matrix synthesized by a sol-gel process. The host matrix of the so-called ureasil is a network of silica to which oligopolyoxyethylene chains [POE, (OCH2CH2)n] are grafted by means of urea cross-links. The free complex and sol-gel materials were characterized by thermal analysis (DSC), surface analysis (XPS) and spectroscopic methods (FT-IR and UV/Vis). The data gathered indicates that the molybdenum(IV) complex is immobilized in the host matrix, and it exhibits structural properties different from those of the free form. These differences could arise either from distortions caused by steric effects imposed by the structure of hybrid matrix or by interactions with the matrix. These materials shows potential applications in heterogeneous catalysis in mild conditions

Improved biosorption for Cr(VI) reduction and removal by Arthrobacter viscosus using zeolite

The aim of the present work was to optimize the reduction and removal of chromium from aqueous solutions by a biosorption system consisting of a bacteria supported on a zeolite. The system proposed combines the biosorption properties of Arthrobacter viscosus, with the ion exchange capacity of NaY zeolite. Experiments were also performed without the zeolite for comparison purposes. Experimental parameters such as solution pH, biomass concentration and initial Cr(VI) concentration were investigated in order to assess their influence on the biosorption system. The results revealed that chromium biosorption was highly pH dependent. The lower pH values favored Cr(VI) reduction, while higher solution pH enhanced total chromium removal. After the optimization of the parameters in study, the highest content of chromium in the zeolite (0.9%) and best uptake (13.0 mgCr/gzeolite) were obtained for the experiment at pH 4, biomass concentration of 5 g L−1 and initial Cr(VI) concentration of 100 mg L−1. After the biosorption process, the samples were characterized by chemical analyses (ICP-AES) and X-ray photoelectron spectroscopy (XPS). The XPS spectra of bacteria revealed that the chromium loaded on the biomass surface was in the trivalent form.Dr. C.S. Rodriguez (C.A.C.T.I., Vigo University, Spain) is gratefully acknowledged for performing and interpreting the XPS analyses. Bruna Silva and Hugo Figueiredo thank FCT - Portugal (Fundacao para a Ciencia e Tecnologia) for the concession of their PhD grants. Cristina Quintelas is thankful to the same institution for the concession of a Pos-Doc grant. This work was partially funded by the Centre of Biological Engineering and Centre of Chemistry (University of Minho, Portugal) through an FEDER-COMPETE, FCT project (ref: FCT PEst-C/QUI/UI0686/2011)