An innovative, fast and facile soft-template approach for the fabrication of porous PDMS for oil-water separation

Oil wastewater and spilled oil caused serious environmental pollution and damage to public health in the last years. Therefore, considerable efforts are made to develop sorbent materials able to separate oil from water with high selectivity and sorption capacity. However most of them are low reusable, with low volume absorption capacity and poor mechanical properties. Moreover, the synthesis is time-consuming, complex and expensive limiting its practical application in case of emergency. Here we propose an innovative approach for the fabrication of porous PDMS starting from an inverse water-in-silicone procedure able to selectively collect oil from water in few seconds. The synthesis is dramatically faster than previous approaches, permitting the fabrication of the material in few minutes independently from the dimension of the sponges. The porous material evidenced a higher volume sorption capacity with respect to other materials already proposed for oil sorption from water and excellent mechanical and reusability properties.This innovative fast and simple approach can be successful in case of emergency, as oil spill accidents, permitting in situ fabrication of porous absorbents

Biogas upgrading by chemical absorption using ammonia rich absorbents derived from wastewater

The use of ammonia (NH3) rich wastewaters as an ecological chemical absorption solvent for the selective extraction of carbon dioxide (CO2) during biogas upgrading to ‘biomethane’ has been studied. Aqueous ammonia absorbents of up to 10,000 gNH3 m−3 demonstrated CO2 absorption rates higher than recorded in the literature for packed columns using 20,000–80,000 g NH3 m−3 which can be ascribed to the process intensification provided by the hollow fibre membrane contactor used in this study to support absorption. Centrifuge return liquors (2325 g m−3 ionised ammonium, NH4+) and a regenerant (477 gNH4+ m−3) produced from a cationic ion exchanger used to harvest NH4+ from crude wastewater were also tested. Carbon dioxide fluxes measured for both wastewaters compared reasonably with analogue ammonia absorption solvents of equivalent NH3 concentration. Importantly, this demonstrates that ammonia rich wastewaters can facilitate chemically enhanced CO2 separation which eliminates the need for costly exogenic chemicals or complex chemical handling which are critical barriers to implementation of chemical absorption. When testing NH3 analogues, the potential to recover the reaction product ammonium bicarbonate (NH4HCO3) in crystalline form was also illustrated. This is significant as it suggests a new pathway for ammonia separation which avoids biological nitrification and produces ammonia stabilised into a commercially viable fertiliser (NH4HCO3). However, in real ammonia rich wastewaters, sodium bicarbonate and calcium carbonate were preferentially formed over NH4HCO3 although it is proposed that NH4HCO3 can be preferentially formed by manipulating both ion exchange and absorbent chemistry

Controlling shell-side crystal nucleation in a gas-liquid membrane contactor for simultaneous ammonium bicarbonate recovery and biogas upgrading

A gas–liquid hollow fibre membrane contactor (HFMC) process has been introduced for carbon dioxide (CO2) separation from biogas where aqueous ammonia (NH3) is used to chemically enhance CO2 absorption and initiate heterogeneous nucleation of the reaction product ammonium bicarbonate at the membrane–solvent interface. Aqueous ammonia absorbents (2–7 M) were initially used in single pass for CO2 separation from a synthetic biogas where nucleation of ammonium bicarbonate crystals was observed at the perimeter of the micropores. Recirculation of the aqueous ammonia absorbent encouraged the growth of ammonium bicarbonate crystals on the shell-side of the membrane that measured several microns in diameter. However, at high aqueous NH3 concentrations (3–7 M), lumen side crystallisation occurred and obstructed gas flow through the lumen of the HFMC. The suggested mechanism for lumen-side crystallisation was absorbent breakthrough into the lumen due to pore wetting which was promoted by low absorbent surface tension at high NH3 concentration. Preferential shell-side nucleation can therefore be promoted by (1) raising surface tension of the absorbent and (2) selection of a membrane with a more regulated pore shape than the PTFE membrane used (d/L 0.065) as both actions can diminish solvent ingress into the pore. This was evidenced using 2 M NH3 absorbent where shell-side crystallisation was evidenced without the onset of lumen side crystallisation. Raising surface tension through the inclusion of salt into the chemical absorbent also promoted greater CO2 flux stability. Importantly, this study demonstrates that chemically enhanced HFMC are an attractive prospect for gas–liquid separation applications where reaction product recovery offers further economic value

Pretreatment of secondary effluents in view of optimal ozone-based AOP removal of trace organic contaminants : bench-scale comparison of efficiency and energy consumption

This study compares the performance of several ozone-based advanced oxidation processes (AOPs), in combination with filtration, in terms of trace organic contaminant (TrOC) removal efficiency and energy and cost requirement. It was shown that the hydroxyl radical ((OH)-O-center dot) scavenging rate of the secondary wastewater effluent decreased as a result of an additional pretreatment step, leading to an increase of ozone and (OH)-O-center dot exposures at the same ozone dose. Adding filtration such as sand filtration or granular activated carbon filtration (GACF) as a pretreatment increased the removal efficiency of TrOCs by all tested ozone-based AOPs and reduced the minimum effective ozone dose for TrOC elimination. When the applied ozone dose is more than this minimum effective ozone dose, the elimination of TrOCs can be observed. For example, because of the use of anion resin filtration, 17 alpha-ethinylestradiol elimination contributed by the process of ozone-based AOP increased from 34.6 to 42.1% at an ozone dose of 1.0 g O-3/g dissolved organic carbon. Ozone-based AOPs coupled with filtration as a pretreatment were found to be more cost-efficient than the single AOPs at all ozone dose levels. The energy consumption of ozone-based AOPs was decreased by more than 25% when applying GACF as a pretreatment. In comparison with other filtration techniques, the pretreatment of secondary effluents by GACF before ozonation was proven to be the most cost-effective method for TrOC elimination

〔報告〕フィルム保管庫における酢酸雰囲気の改善の試み

Concentration of acetic acid in cabinets, film storage and adjacent room were measured. Two cabinets were filled with acetic acid generated from aged microfilms. Absorbents were placed in one of the cabinets to remove acetic acid. It was confirmed thatconcentration of acetic acid decreased one week after setting the absorbents. Concentration in the other cabinet in which acetic-acid-absorbents were not placed remained high. From this result, it may be said that the absorbents were effective in reducing acetic acid from the first cabinet. Some amount of acetic acid was detected in the film storage. This is probably due to leakage from the cabinets. Similarly, some amount of acetic acid was detected in the adjacent room. This is probably due to leakage from the film storage

Dyes removal from water using low cost absorbents

In this study, the removal capacity of low cost adsorbents during the adsorption of Methylene Blue (MB) and Congo Red (CR) at different concentrations (50 and 100mg•L-1) was evaluated. These adsorbents were produced from wood wastes (cedar and teak) by chemical activation (ZnCl2). Both studied materials, Activated Cedar (AC) and activated teak (AT) showed a good fit of their experimental data to the pseudo second order kinetic model and Langmuir isotherms. The maximum adsorption capacities for AC were 2000.0 and 444.4mg•g-1 for MB and CR, respectively, while for AT, maximum adsorption capacities of 1052.6 and 86.4mg•g-1 were found for MB and CR, respectively. © Published under licence by IOP Publishing Ltd

Aldehyde-containing urea-absorbing polysaccharides

A novel aldehyde containing polymer (ACP) is prepared by reaction of a polysaccharide with periodate to introduce aldehyde groups onto the C2 - C3 carbon atoms. By introduction of ether and ester groups onto the pendant primary hydroxyl solubility characteristics are modified. The ACP is utilized to absorb nitrogen bases such as urea in vitro or in vivo

Atmospheric Research and Monitoring Study of Hazardous Substances

Hazardous Waste Research and Information Center Illinois Department of Energy and Natural Resources