J.A. Muñoz

Biosorption of cadmium, lead and copper with calcium alginate xerogels and immobilized Fucus vesiculosus.

This paper determines the effect of immobilized brown alga Fucus vesiculosus in the biosorption of heavy metals with alginate xerogels. Immobilization increased the kinetic uptakes and intraparticle diffusion rates of the three metals. The Langmuir maximum biosorption capacity increased twofold for cadmium, 10 times for lead, and decreased by half for copper. According to this model, the affinity of the metals for the biomass was as follows: Cu>Pb>Cd without alga and Pb>Cu>Cd with alga. FITR confirmed that carboxyl groups were the main groups involved in the metal uptake. Calcium in the gels was displaced by heavy metals from solution according to the egg-box model. The restructured gel matrix became more uniform and organized as shown by scanning electron microscopy (SEM) characterization. F. vesiculosus immobilized in alginate xerogels constitutes an excellent biosorbent for cadmium, lead and copper, sometimes surpassing the biosorption performance of alginate alone and even the free alga.

Iron Speciation in Dissimilatory Fe(III)-reducing Cultures

A protocol has been developed for determination of iron distribution and speciation in the solid and liquid phases of dissimilatory Fe(III)-reducing bacteria cultures. Sampling methods and sample processing have been improved. Three different extraction conditions have been tested for iron measurement: hydrochloric acid, ammonium oxalate and hydroxylamine hydrochloride. Separate collection of samples for liquid and solids analysis was tested, providing the best insight into Fe distribution. One sample was taken from the aqueous phase after solid settlement in vials to determine the concentration of dissolved iron species; the other was taken from agitated flasks, in which iron was extracted from solids prior to the analysis. Extraction with HCl 1Mfor 24 h proved the least labor-intensive procedure, with extraction efficiency adequate for our purposes. The extractant properties of HCl, less aggressive than the others, dissolved only the bio-available fraction of Fe(III).

Continuous metal biosorption applied to industrial effluents: a comparative study using an agricultural by-product and a marine alga

AbstractFixed-bed column experiments have been conducted to evaluate the removal of metals from real industrial wastewaters. nThe effluents tested were provided by two different metallurgical companies: Industrial Goñabe, a galvanizing plant, and Sao Domingos mine, an abandoned sulfide mine. Sugar-beet pulp, a by-product of the sugar industry, and brown alga Fucus vesiculosus were used as biosorbents. The influence of pH on the sorption process was insignificant for the tests using Industrial Goñabe wastewater. On the contrary, an increase of pH improved metal sorption uptake and yield and saturation rate in the case of the Sao Domingos wastewater. A lower metal concentration in Sao Domingos wastewater resulted in a higher availability of metal-binding sites on the biomass. Better sorption parameters for both real wastewaters were obtained using brown alga Fucus vesiculosus. At pH 5, Zn sorption in continuous mode increased from 36 to 48% for Industrial Goñabe wastewater and from 34 to 37% for Sao Domingos wastewater. In the latter case, copper sorption increased from 73 to 88%. Breakthrough points that determine the service time of columns were reached later using alga as biosorbent. For Zn, column adsorption performance improved substantially with alga and its service time by 5 times. In the case of Cu, the breakthrough point of the second column was not reached during 1750xa0min of experimentation. nThe results obtained reaffirm the industrial applicability of these techniques.

Interrelation between Cells and Extracellular Polymeric Substances (EPS) from Acidiphilium 3.2Sup(5) on Carbon Surfaces

The interrelation between cells and extracellular polymeric substances (EPS) from the acidophilic bacterium Acidiphilium 3.2Sup(5) was investigated on two different carbon surfaces (carbon fibre cloth and graphite rods). This bacterium was chosen due to its ability to directly transfer electrons to carbon surfaces in aerobic conditions, which makes its use especially attractive in microbial fuel cells (MFC). The characterization of the bacterial adhesion and interrelation with the EPS was carried out using a combination of scanning (SEM) and transmission (TEM) electron microscopy. The extraction of the EPS was performed using EDTA and their characterization accomplished by chemical analyses and FTIR spectroscopy. The cellular lysis provoked by the extraction of EPS was determined by the protein/carbohydrate ratio. Chemical analyses showed that the main components of the EPS were proteins and carbohydrates, whereas FTIR spectroscopy showed the presence of a great majority of carboxyl, hydroxyl and amino groups. The tendency of cells was to adhere to superficial carbon imperfections, which after certain time were covered by a matrix of EPS.

The Influence of Disimilatory Fe(III) Reducers on Iron Ore Dissolution

The biological reduction rate of Fe(III) was studied using dissimilatory ferric reducing bacterial cultures (FeRB) in an attempt to establish a biotechnological via for the metallurgical treatment of iron ores. Enrichment cultures of dissimilatory ferric reducers were obtained from samples collected from a flooded acidic open pit in an abandoned Pb and Zn sulphide mining site nearby La Unión (Murcia, Spain). Adapted cultures were able to reduce 3 g/L of soluble Fe(III) with 100 efficiency in 36 hours. The growth of mixed cultures was also tested in solids. Ferrihydrite and ammonium jarosite served as electron acceptors in cultures where lactate acted as electron donor. Bacterial growth was also positive in both cases. This result represents an effective alternative to the chemical reduction of ferric minerals that avoids extreme temperatures when pyrometallurgical reactors are used. In addition, three species of FeRB were isolated and identified as Serratia fonticola, Aeromonas hydrophila and Clostridium celerecrescens. One of them, Aeromonas hydrophila, results of particular interest and, at the present moment, is being studied in depth. The particular significance of Aeromonas hydrophila is related to the characteristics of its exhausted cultures, where ferrous iron remains solved at pH values next to 7. At the present moment, the identification and characterization of the Fe(II) soluble complex is being account.

Mechanisms involved in sorption of metals by chemically treated waste biomass from irrigation pond

AbstractnSeveral analytical techniques (FTIR, SEM–EDS and acid–base titration) have been used to characterize an irrigation pond biomass after chemical modification with different pretreatment agents (NaHCO3, Na2CO3 and NaOH, with and without a subsequent washing treatment) in order to explain the observed increase in different metals sorption uptake (Cd2+, Cu2+, Ni2+, Pb2+ and Zn2+). It was found that chemical pretreatments favoured anchoring of Na+ on the active sites of the biomass and in turn metal uptake by ion exchange. In addition, higher cell wall porosity was observed, which increased the availability of new innermost active centres in the biomass. The active sites were loaded with Ca2+, which was also involved in the metal ion exchange process.

Scratch as Educational Tool to Introduce Robotics

There are many necessities that need to be improved in STEM (Science, Technology, Engineering and Math) education. The robotics represents a promising educational tool. Nowadays, robotic education tools arise with the aim of promoting the innovation and the motivation of the students during the learning process. Robots are becoming more common in our daily life; thus, it is important to integrate robots at all levels of our society. The aim of this paper is to present the use of Scratch - a widely-used tool - in order to guide educational robotics as the first step in introducing students into robotics. The robotics requires several skills such as systems thinking, programming mindset, active learning, mathematics, science, judgement and decision making, good communication, technology design, complex problem solving and persistence. These skills can be easily developed using Scratch. The obtained outcomes from the educational robotic course demonstrate how children without previous experience in programming or robotics can start learning both through experiences in the classroom. The result of this work shows that it is better to make very easy challenges, to adapt the difficulty to each of the children. Furthermore, it is necessary to develop previous concepts. Moreover, it is necessary to work the design, instead of programming directly. Additionally, it is important to combine theory and practice with the aim of including fun tasks intertwined with the challenges that are posed to apply theory in problem solving.

Bioremediation of Sulfide Mine Tailings: Response of Different Soil Fractions

Bioremediation phenomena of soils contaminated with heavy metals have not been considered a key sustainability issue for the mining industry until recently. At least, this is what can be deduced from the huge amount of mining activities spread out worldwide. Nevertheless, mine wastes accumulated over long periods of time have a negative impact on the landscape and pose serious threats to ecosystems. Far from being solved, this issue is becoming more acute as the metalliferous mining industry is seriously affected by the cutoff grades decline of natural resources. The mining district of Sierra Cartagena-La Union in southeast Spain, with a total area of 100 km2, is a good example of poor mine practices. Metal extraction (Ag, Pb, and Zn) from sulfide mineral ores in this mining area dates back before Roman times. Consequently, large amounts of mining wastes have been accumulated over the centuries close to human settlements. Facts like this, underestimated in the past, could be a potential source of metal propagation with possible detrimental effects on human health. In this work, a bioremediation study has been accomplished in a metalliferous contaminated soil considering different particle size fractions. Each fraction, including the global material waste, has been chemically characterized using an ad hoc approach, followed by its mineralogical characterization. The investigation has been focused on the effect of bioaugmentation on metal mobilization and redistribution of heavy metals (Zn, Pb, Cu, Fe) among different soil fractions.