Resource recovery and remediation of highly alkaline residues : a political-industrial ecology approach to building a circular economy

Highly alkaline industrial residues (e.g., steel slag, bauxite processing residue (red mud) and ash from coal combustion) have been identified as stocks of potentially valuable metals. Technological change has created demand for metals, such as vanadium and certain rare earth elements, in electronics associated with renewable energy generation and storage. Current raw material and circular economy policy initiatives in the EU and industrial ecology research all promote resource recovery from residues, with research so far primarily from an environmental science perspective. This paper begins to address the deficit of research into the governance of resource recovery from a novel situation where re-use involves extraction of a component from a bulk residue that itself represents a risk to the environment. Taking a political industrial ecology approach, we briefly present emerging techniques for recovery and consider their regulatory implications in the light of potential environmental impacts. The paper draws on EU and UK regulatory framework for these residues along with semi-structured interviews with industry and regulatory bodies. A complex picture emerges of entwined ownerships and responsibilities for residues, with past practice and policy having a lasting impact on current possibilities for resource recovery

Development of paper-based color test-strip for drug detection in aquatic environment: Application to oxytetracycline

The wide use of antibiotics in aquaculture has led to the emergence of resistant microbial species. It should be avoided/minimized by controlling the amount of drug employed in fish farming. For this purpose, the present work proposes test-strip papers aiming at the detection/semi-quantitative determination of organic drugs by visual comparison of color changes, in a similar analytical procedure to that of pH monitoring by universal pH paper. This is done by establishing suitable chemical changes upon cellulose, attributing the paper the ability to react with the organic drug and to produce a color change. Quantitative data is also enabled by taking a picture and applying a suitable mathematical treatment to the color coordinates given by the HSL system used by windows. As proof of concept, this approach was applied to oxytetracycline (OXY), one of the antibiotics frequently used in aquaculture. A bottom-up modification of paper was established, starting by the reaction of the glucose moieties on the paper with 3-triethoxysilylpropylamine (APTES). The so-formed amine layer allowed binding to a metal ion by coordination chemistry, while the metal ion reacted after with the drug to produce a colored compound. The most suitable metals to carry out such modification were selected by bulk studies, and the several stages of the paper modification were optimized to produce an intense color change against the concentration of the drug. The paper strips were applied to the analysis of spiked environmental water, allowing a quantitative determination for OXY concentrations as low as 30 ng/mL. In general, this work provided a simple, method to screen and discriminate tetracycline drugs, in aquaculture, being a promising tool for local, quick and cheap monitoring of drugs

Electrokinetic delivery of persulfate to remediate PCBs polluted soils: Effect of different activation methods

Persulfate-based in-situ chemical oxidation (ISCO) for the remediation of organic polluted soils has gained much interest in last decade. However, the transportation of persulfate in low-permeability soil is very low, which limits its efficiency in degrading soil pollutants. Additionally, the oxidation-reduction process of persulfate with organic contaminants takes place slowly, while, the reaction will be greatly accelerated by the production of more powerful radicals once it is activated. Electrokinetic remediation (EK) is a good way for transporting persulfate in low-permeability soil. In this study, different activation methods, using zero-valent iron, citric acid chelated Fe²⁺, iron electrode, alkaline pH and peroxide, were evaluated to enhance the activity of persulfate delivered by EK. All the activators and the persulfate were added in the anolyte. The results indicated that zero-valent iron, alkaline, and peroxide enhanced the transportation of persulfate at the first stage of EK test, and the longest delivery distance reached sections S4 or S5 (near the cathode) on the 6th day. The addition of activators accelerated decomposition of persulfate, which resulted in the decreasing soil pH. The mass of persulfate delivered into the soil declined with the continuous decomposition of persulfate by activation. The removal efficiency of PCBs in soil followed the order of alkaline activation > peroxide activation > citric acid chelated Fe²⁺ activation > zero-valent iron activation > without activation > iron electrode activation, and the values were 40.5%, 35.6%, 34.1%, 32.4%, 30.8% and 30.5%, respectively. The activation effect was highly dependent on the ratio of activator and persulfate

Bioleaching for resource recovery from low-grade wastes like fly and bottom ashes from municipal incinerators: A SWOT analysis

Bioleaching (or microbial leaching) is a biohydrometallurgical technology that can be applied for metal recovery from anthropogenic waste streams. In particular, fly ashes and bottom ashes of municipal solid waste incineration (MSWI) can be used as a target material for biomining. Globally, approximately 46 million tonnes of MSWI ashes are produced annually. Currently landfilled or used as aggregate, these contain large amounts of marketable metals, equivalent to low-grade ores. There is opportunity to recover critical materials as the circular economy demands, using mesophile, moderately thermophile, and extremophile microorganisms for bioleaching. A Strengths, Weaknesses, Opportunities and Threats (SWOT) analysis was developed to assess the potential of this biotechnology to recover critical metals from MSWI wastes. Bioleaching has potential as a sustainable technology for resource recovery and enhanced waste management. However, stakeholders can only reap the full benefits of bioleaching by addressing both the technical engineering challenges and regulatory requirements needed to realise and integrated approach to resource use

Numerical prediction of diffusion and electric field-induced iron nanoparticle transport

Zero valent iron nanoparticles (nZVI) are considered very promising for the remediation of contaminated soils and groundwaters. However, an important issue related to their limited mobility remains unsolved. Direct current can be used to enhance the nanoparticles transport, based on the same principles of electrokinetic remediation. In this work, a generalized physicochemical model was developed and solved numerically to describe the nZVI transport through porous media under electric field, and with different electrolytes (with different ionic strengths). The model consists of the Nernst–Planck coupled system of equations, which accounts for the mass balance of ionic species in a fluid medium, when both the diffusion and electromigration of the ions are considered. The diffusion and electrophoretic transport of the negatively charged nZVI particles were also considered in the system. The contribution of electroosmotic flow to the overall mass transport was included in the model for all cases. The nZVI effective mobility values in the porous medium are very low (10−7–10−4 cm2 V−1 s−1), due to the counterbalance between the positive electroosmotic flow and the electrophoretic transport of the negatively charged nanoparticles. The higher the nZVI concentration is in the matrix, the higher the aggregation; therefore, low concentration of nZVI suspensions must be used for successful field application.This work has been funded by the research grant SFRH/BD/76070/2011, by project PTDC/AGR-AAM/101643/2008 NanoDC under Portuguese National funds through “Fundação para a Ciência e a Tecnologia” and by FP7-PEOPLE-IRSES-2010-269289-ELECTROACROSS. The Department of Civil and Environmental Engineering at Lehigh University is acknowledged for the funding of equipment development, testing and analysis of the nZVI transport experiments

Evaluation of photoanode materials used in biophotovoltaic systems for renewable energy generation

Biological photovoltaic (BPV) cells are living solar panels capable of producing clean energy by extracting electrons from sunlight (in daytime) and stored carbon in microbial cells (during the night or on cloudy days), irrespective of the organic substrate supply. The physicochemical properties of anode surfaces harbouring microbial communities in BPV systems influence the electrochemical charge transfer rate at the electrode. Hence, these properties play a significant role in regulating the kinetics of metabolic reactions in the biotic compartment while providing an electron transfer path. Various electrically conductive materials have been explored as solid-state anodes to improve the power output and economic viability of BPV systems. However, the current systems still suffer from low power density due to electrodes' electrochemical limitations and a lack of systematic optimization of the device. This review provides a comprehensive insight into the recent developments in different anode materials, their dimensional structure, and their impact on the performance of BPV systems in the last two decades. Moreover, the existing limitations of electrode materials in BPV systems are summarized, and outlooks for future anode advancements are foreseen

Methanogenesis from Mineral Carbonates, a Potential Indicator for Life on Mars

Priorities for the exploration of Mars involve the identification and observation of biosignatures that indicate the existence of life on the planet. The atmosphere and composition of the sediments on Mars suggest suitability for anaerobic chemolithotrophic metabolism. Carbonates are often considered as morphological biosignatures, such as stromatolites, but have not been considered as potential electron acceptors. Within the present study, hydrogenotrophic methanogen enrichments were generated from sediments that had received significant quantities of lime from industrial processes (lime kiln/steel production). These enrichments were then supplemented with calcium carbonate powder or marble chips as a sole source of carbon. These microcosms saw a release of inorganic carbon into the liquid phase, which was subsequently removed, resulting in the generation of methane, with 0.37 ± 0.09 mmoles of methane observed in the steel sediment enrichments supplemented with calcium carbonate powder. The steel sediment microcosms and lime sediments with carbonate powder enrichments were dominated by Methanobacterium sp., whilst the lime/marble enrichments were more diverse, containing varying proportions of Methanomassiliicoccus, Methanoculleus and Methanosarcina sp. In all microcosm experiments, acetic acid was detected in the liquid phase. Our results indicate that chemolithotrophic methanogenesis should be considered when determining biosignatures for life on Mars

Options for managing alkaline steel slag leachate: A life cycle assessment

Management of steel slag (a major by-product of the steel industry) includes the treatment of highly alkaline leachate (pH > 11.5) from rainwater infiltration of slag deposits to prevent adverse impact upon surface or ground waters. This study aims to compare different treatment options for steel slag leachate through a life cycle assessment (LCA). Five options were compared: active treatment by acid dosing (A-H2SO4), active treatment by carbon dioxide dosing (A-CO2), active treatment by calcium chloride dosing (A-CaCl2), passive treatment by cascade and reedbeds with pumping (P-P), and passive treatment by cascade and reedbeds in a gravity-driven configuration (P-G). The functional unit was 1 m3 of treated leachate with pH < 9, considering 24 h and 365 days of operating, maintenance operations every year, and service life of 20 years. Inventory data were obtained from project designers, commercial suppliers, laboratory data and field tests. The environmental impacts were calculated in OpenLCA using the ELCD database and ILCD 2011 method, covering twelve impact categories. The A-CaCl2 option scored worse than all other treatments for all considered environmental impact categories. Regarding human toxicity, A-CaCl2 impact was 1260 times higher than the lowest impact option (A-CO2) for carcinogenics and 53 times higher for non-carcinogenics (A-H2SO4). For climate change, the lowest impact was calculated for P-G < P-P < A-H2SO4 < A-CO2 < A-CaCl2, while for particulate matter/respiratory inorganics, the options ranked as follows P-G < P-P < A-CO2 < A-H2SO4 < A-CaCl2. The major contributor to these impact categories was the Solvay process to produce CaCl2. Higher uncertainty was associated with the categories particulate matter formation, climate change and human toxicity, as they are driven by indirect emissions from electricity and chemicals production. Both passive treatment options had better environmental performance than the active treatment options. Potential design measures to enhance environmental performance of the treatments regarding metal removal and recovery are discussed and could inform operational management at active and legacy steel slag disposal sites

Recovery of Al, Cr and V from steel slag by bioleaching: batch and column experiments

Steel slag is a major by-product of the steel industry and a potential resource of technology critical elements. For this study, a basic oxygen furnace (BOF) steel slag was tested for bacterial leaching and recovery of aluminium (Al), chromium (Cr), and vanadium (V). Mixed acidophilic bacteria were adapted to the steel slag up to 5% (w/v). In the batch tests, Al, Cr, and V were bioleached significantly more from steel slag than in control treatments. No statistical difference was observed arising from the duration of the leaching (3 vs 6 d) in the batch tests. Al and Cr concentrations in the leachate were higher for the smaller particle size of the steel slag (< 75 µm), but no difference was observed for V. In the column tests, no statistical difference was found for pH, Al, Cr and V between the live culture (one-step bioleaching) and the supernatant (two-step bioleaching). The results show that the culture supernatant can be effectively used in an upscaled industrial application for metal recovery. If bioleaching is used in the 170-250 million tonnes of steel slag produced per year globally, significant recoveries of metals (100% of Al, 84% of Cr and 8% of V) can be achieved, depending on the slag composition. The removal and recovery percentages of metals from the leachate with Amberlite®IRA-400 are relatively modest (< 67% and < 5%, respectively), due to the high concentration of competing ions (SO42-, PO43-) in the culture medium. Other ion exchange resins can be better suited for the leachate or methods such as selective precipitation could improve the performance of the resin. Further research is needed to minimise interference and maximise metal recovery

Humor in mathematics teaching

HUMOR: OUR VIEW FOR MATHEMATICS TEACHING Our assumptions and context. Process humor and be able to produce is clearly a sign of intelligence, revealing, when done well, complex reasoning. Humor has an important social role, assuming as a cognitive experience that as well as creating a sense of well-being, predisposes people to work and can improve the productivity of that work. Mathematics is a discipline in which the reasoning occupies a very prominent place, both as a science as a school area. At the same time, students' interest for mathematics is not always the same and some have initially not very favorable feelings (Toh, 2009; Wanzer, Frymier & Irwin, 2010). Recent curriculum changes to the teaching of mathematics have been, in most countries of the world, showing the need for students to develop skills of critical nature, such as communication, thinking and problem solving along with the acquisition of mathematical knowledge. Also in Portugal, it is claimed the importance of promoting learning that combine the construction of mathematical knowledge with its use, when performing mathematical tasks and communicating mathematical ideas and mathematical reasoning. In the early years of schooling, corresponding to primary education in many countries, the use of texts such as short stories or comics, from which we can develop challenging mathematical tasks, is reported in the literature as having potential to promote learning specified in curricular documents (Wanzer, Frymier., & Irwin, 2010). In particular, some texts focus on mathematical topics in a humorous way and to be understood, students must develop their mathematical competence. The development of mathematical tasks from stories and other humorous presents big challenges to teachers (Flores & Moreno, 2011). Our questions. In this context, we put some questions: Primary teachers use in their classes tasks or situations that present, in a humorous way, mathematical ideas? What resources do they use? Also: How to select, adapt or build texts and tasks which have, in a humorous way, mathematical ideas with didactic potential for education in the early years of schooling? If the resources for this purpose have been produced and if teachers have been sensitized for their use, are they able to integrate them in their classes? Our intentions. This research project seeks to address these questions, focused on: (i ) assessment of teachers’ practices and underlying knowledge, resources available for the use of texts with mathematical ideas presented in a humorous way; (ii) selection, adaptation and construction of mathematical tasks from texts that present, in a humorous way, mathematical ideas with didactic potential in education for the early years of schooling; and ( iii ) integration and use, by primary school teachers, of texts that present , in a humorous way, contexts for the teaching of mathematics. So, the project is organized into three tasks and as a methodological design that combines qualitative elements with quantitative elements, the first one prevailing