The removal of arsenic from （ground）-water by adsorbent loaded in polymeric microspheres

Arsenic is a natural tasteless and odourless element,existing in the earth’s crust at average levels of between two and five thousands micrograms per liter (parts per million) . Arsenic is highly toxic to humans, who are exposed to it primarily from air,food and water. The occurrence of arsenic in groundwater is due to geological composition of soil. High concentrations of arsenic in water are the result of dissolution or desorption of ferric oxides and the oxidation of mineral arsenopyrites. Arsenic in drinking water has an important impact on the human health,especially in the less developed countries. Different methods exist to remove arsenic from aquatic media,and one of them is by adsorption. In this work,the adsorption of both As(III) and As(V) by means of novel microspheres has been investigated. In particular,TiO2 has been embedded into polymeric microspheres PES (PolyEtherSulphone) and PEEK-WC (PolyEtherEther-Ketone) . The main advantages of this encapsulation adsorption material are: no loss of adsorbents into the water stream,easy to be used and scaled-up.     

Investigating the effect of SPRM on mechanical strength and thermal conductivity of highly porous alumina ceramics

For recycling waste refractory materials in metallurgical industry, porous alumina ceramics were prepared via pore forming agent method from α-Al₂O₃ powder and slide plate renewable material. Effects of slide plate renewable material (SPRM) on densification, mechanical strength, thermal conductivity, phase composition and microstructure of the porous alumina ceramics were investigated. The results showed that SPRM effectively affected physical and thermal properties of the porous ceramics. With the increase of SPRM, apparent porosity of the ceramic materials firstly increased and then decreased, which brought an opposite change for the bulk density and thermal conductivity values, whereas the bending strength didn’t decrease obviously. The optimum sample A2 with 50 wt% SPRM introducing sintered at 1500 °C obtained the best properties. The water absorption, apparent porosity, bulk density, bending strength and thermal conductivity of the sample were 31.7%, 62.8%, 1.71 g/cm³, 47.1 ± 3.7 MPa and 1.73 W/m K, respectively. XRD analysis indicated that a small quantity of silicon carbide and graphite in SPRM have been oxidized to SiO₂ during the firing process, resulting in rising the porous microstructures. SEM micrographs illustrated that rod-like mullite grains combined with plate-like corundum grains to endow the samples with high bending strength. This study was intended to confirm the preparation of porous alumina ceramics with high porosity, good mechanical properties and low thermal conductivity by using SPRM as pore forming additive.     

Hydrogen production from methane steam reforming: parametric and gradient based optimization of a Pd-based membrane reactor

In this work three mathematical models for methane steam reforming in membrane reactors were developed. The first one is a steady state, non isothermal, non isobaric and one dimensional model derived from material and energy balances and validated using experimental data from the literature. It is referred as full model. The influence of two different intrinsic kinetics available, as well as, the influence of five important parameters on methane conversion (X_CH4_{\mathrm{CH}_{4}}) and hydrogen recovery (Y_H2_{\mathrm{H}_{2}}) were parametrically evaluated through simulations. The second model, referred as meta-model, was obtained though the response surface technique. This meta-model was included into a constrained optimization problem solved using NPSOL. The third model, referred as a simplified model, takes into account only mass balances from the full model. Using this model, a gradient based method (DIRCOL) was used to perform the optimization of the sum of methane conversion and hydrogen recovery. High methane conversions and hydrogen recoveries were reached through these methodologies.     

Boron removal by membrane contactors: the water that purifies water

The potential of membrane contactors for treating boron containing waters were investigated. In particular, experimental tests at lab scale on flat membrane modules with 40 cm² of membrane area were carried out, to identify the effect of different parameters, such as temperature, flow rate, boron concentration, etc. on the efficiency of the process. Water was chosen as the extractant in order to avoid the pollution of the feed stream and two symmetric microporous hydrophilic flat membranes with different pore size and porosity were used. From these tests, it results that the boron removal increases with the extractant temperature and with the operating flow rates. However, it is independent on the initial boron concentration in the feed water. Moreover, higher removals are obtained with the membrane with larger pore size and higher porosity. Based on the experimental results, an integrated reverse osmosis-membrane contactor system, where the membrane contactor works on the reverse osmosis permeate, was proposed and designed for a 100 m³/h fresh water production (with a boron content ≤0.4 ppm). In particular, membranes with higher porosity and lower thickness than those used in the experimental tests were considered for the calculations, in order to work at 25°C (so, there is no need of heating the extractant stream) with reasonable membrane areas. The comparison of the proposed plant to that actually used, has shown that the proposed one appears to be more effective in terms of size, energy and chemical consumption, flexibility and modularity.     

Methane steam reforming in a Pd-Ag membrane reformer: An experimental study on reaction pressure influence at middle temperature

In this experimental work, methane steam reforming (MSR) reaction is performed in a dense Pd-Ag membrane reactor and the influence of pressure on methane conversion, CO_x-free hydrogen recovery and CO_x-free hydrogen production is investigated. The reaction is conducted at 450 °C by supplying nitrogen as a sweep gas in co-current flow configuration with respect to the reactants. Three experimental campaigns are realized in the MR packed with Ni-ZrO catalyst, which showed better performances than Ni-Al₂O₃ used in a previous paper dealing with the same MR system. The first one is directed to keep constant the total pressure in both retentate and permeate sides of the membrane reactor. In the second case study, the total retentate pressure is kept constant at 9.0 bar, while the total permeate pressure is varied between 5.0 and 9.0 bar. As the best result of this work, at 450 °C and 4.0 bar of total pressure difference between retentate and permeate sides, around 65% methane conversion and 1.2 l/h of CO_x-free hydrogen are reached, further recovering 80% CO_x-free hydrogen over the total hydrogen produced during the reaction. Moreover, a study on the influence of hydrogen-rich gas mixtures on the hydrogen permeation through the Pd-Ag membrane is also performed and discussed.     

Impact of different weather years on the design of hydrogen supply pathways for transport needs

Renewable energy sources (RES) will play a crucial role in future sustainable energy systems. In scenarios analyzing future energy system designs, a detailed spatial and temporal representation of renewable-based electricity generation is essential. For this, sufficiently representative weather data are required. Most analyses performed in this context use the historical data of either one specific reference year or an aggregation of multiple years. In contrast, this study analyzes the impact of different weather years based on historical weather data from 1980 through 2016 in accordance with the design of an exemplary future energy system. This exemplary energy system consists of on- and offshore wind energy for power-to-hydrogen via electrolysis, including hydrogen pipeline transport for most southwestern European countries. The assumed hydrogen demand for transportation needs represents a hypothetical future market penetration for fuel cell-electric vehicles of 75%. An optimization framework is used in order to evaluate the resulting system design with the objective function of minimizing the total annual cost (TAC) of the system. For each historical weather year, the applied optimization model determines the required capacities and operation of wind power plants, electrolyzers, storage technologies and hydrogen pipelines to meet the assumed future hydrogen demand in a highly spatially- and temporally-detailed manner, as well as the TAC of the system. Following that, the results of every individual year are compared in terms of installed capacities, overall electricity generation and connection to the transmission network, as well as the cost of these components within each region. The results reveal how sensitive the final design of the exemplary system is to the choice of the weather year. For example, the TAC of the system changes by up to 20% across two consecutive weather years. Furthermore, significant variation in the optimization results regarding installed capacities per region with respect to the choice of weather years can be observed.     

Perovsldte-type oxygen-permeable membrane BaCo0.7Fe0.2Nb0.1O3-δ for partial oxidation of methane in coke oven gas to hydrogen

Perovskite-type oxygen-permeable membrane reactors of BaCo_0.7Fe_0.2Nb_0.1O_3−δ (BCFNO) packed with Ru-based catalyst had high oxygen permeability and could be used for hydrogen production by partial oxidation of methane in coke oven gas (COG). At 1173 K, 94% of methane conversion, 85% of H2 selectivity, 107% of CO selectivity, and as high as 15.4 mL·cm⁻²·min⁻¹ of oxygen permeation flux were obtained. The BCFNO membrane itself had poor catalytic activity to partial oxidation of CH₄ in COG. During continuous operation for 70 h at 1173 K, no degradation of the membrane reaction performance was observed. XRD and SEM characterization also demonstrated that the BCFNO membrane reactor exhibited good stability in partial oxidation of methane in COG.     

Air gap membrane distillation on the different types of membrane

Seawater desalination through the air gap membrane distillation (AGMD) process shows merit for its ambient operational conditions and low energy consumption. In this paper nine types of commercially available membranes were characterized to understand the membranes more comprehensively. The density, porosity, mean pore radius, liquid entry pressure (LEP), and contact angle (CA) of the membranes were determined. AGMD experiments were performed for the membranes to investigate the membrane difference on permeation flux and salt rejection. The effects of operating parameters such as temperature, flow rate, and NaCl concentration were studied. The 0.22 μm pore size PTFE membrane showed excellent performance for its higher permeability and higher hydrophobicity than other membranes. The mass transfer coefficients for three types of PTFE membranes were calculated from the results of the experiments.