High-capacity and selective ammonium removal from water using sodium cobalt hexacyanoferrate

A new NH4+adsorbent with high capacity and selectivity, sodium cobalt(II) hexacyanoferrate(II) ( NaCoHCF, NayCo (II) [Fe2+(CN)6]x$zH2O), was prepared. The adsorption performance was investigated by varying the mixing ratio of [Fe (CN) 6 ] 4-to Co2+ during synthesis, Rmix. The ammonia capacity was found to be proportional to Rmix, indicating that the NH4+ capacity can be increased by increasing the Na+-ion content in NaCoHCF. To conduct a detailed study, we prepared homogeneous nanoparticles by flow synthesis using a micromixer withRmix¼1.00. Even on the addition of a saline solution (NaCl) with anNa+-ion concentration of 9350 mg L−1, the capacity was maintained : qmax¼ 4.28 mol kg−1. Using Markham–Benton analysis, the selectivity factor, defined by the ratio of equilibrium constants for NH4+to that for Na+, was calculated to bea¼96.2, and 4.36 mol kg−1was found to be the maximum capacity. The high selectivity of NaCoHCF results in good NH4+-adsorption performance, even from seawater. In comparison with other adsorbents under the same conditions and even for a NH4Clsolution, NaCoHCF showed the highest capacity. Moreover, the coexisting Na+caused no interference with the adsorption of ammonium by NaCoHCF, whereas the other adsorbents adsorbed ammonia only slightly from the saline solution. We also found that the pores for NH4+adsorption changed their sizes and shapes after adsorption

Decontamination of Radioactive Cesium Released from Fukushima Daiichi Nuclear Power Plant -13277

ABSTRACT Peculiar binding of Cesium to the soil clay minerals remained the major obstacle for the immediate Cs-decontamination of soil and materials containing clay minerals like sludge. Experiments for the removal of Cesium from soil and ash samples from different materials were performed in the lab scale. For soil and sludge ash formed by the incineration of municipal sewage sludge, acid treatment at high temperature is effective while washing with water removed Cesium from ashes of plants or burnable garbage. Though total removal seems a difficult task, water-washing of wood-ash or garbage-ash at 40 ºC removes >90% radiocesium, while >60% activity can be removed from soil and sludge-ash by acid washing at 95 ºC

Desorption of Ammonia Adsorbed on Prussian Blue Analogs by Washing with Saturated Ammonium Hydrogen Carbonate Solution

Prussian blue analogs (PBAs) have been reported as promising ammonia (NH3) adsorbents with a high capacity compared to activated carbon, zeolite, and ion exchange resins. The adsorbed NH3 was desorbed by heating and washing with water or acid. Recently, we demonstrated that desorption was also possible by washing with a saturated ammonium hydrogen carbonate solution (sat. NH4HCO3aq) and recovered NH3 as an NH4HCO3 solid by introducing CO2 into the washing liquid after desorption. However, this has only been proven for copper ferrocyanide and the relationship between the adsorption/desorption behavior and metal ions in PBAs has not been identified. In this study, we investigated the adsorption/desorption behavior of PBAs that are complexes of first row transition metals with hexacyanometalate anions. Six types of PBAs were tested in this study and copper ferricyanide exhibited the highest desorption/adsorption ratio. X-ray diffraction results revealed high structural stability for cobalt hexacyanocobaltate (CoHCC) and nickel ferricyanide (NiHCF). The Fourier transform infrared spectroscopy results showed that the NH3 adsorbed on the vacancy sites tended to desorb compared to the NH3 adsorbed on the interstitial sites as ammonium ions. Interestingly, the desorption/adsorption ratio exhibited the Irving-Williams order

Life Cycle Assessment of Nitrogen Circular Economy-Based NOx Treatment Technology

Humans are significantly perturbing the global nitrogen cycle, leading to excess reactive nitrogen in the environment. Nitrogen oxides as a key reactive nitrogen species are mainly controlled by selective non-catalytic reduction and selective catalytic reduction. Converting nitrogen oxides to ammonia, defined as ReNOx, emerges as an alternative method under a disparate design concept. However, little is known about its overall environmental performance. In this study, we conducted for the first time a life cycle assessment of ReNOx. Compared with the eco-index in the condition of 200 °C with a conversion rate of 95%, it would increase substantially in the condition of 160 °C with a conversion rate of 80% and in the case without a sound NH3 treatment. Feedstock format change, adsorption material performance deterioration, and recovery rate decline would increase the eco-index by 8%, 12%, and 18%, respectively. The eco-index was decreased by 31% in the optimized scenario with a renewable energy source and an increased conversion rate. The environmental impacts were compared with traditional methods at impact, damage, and eco-index levels. Finally, the implications on process arrangement in the flue gas system, the externality for power generation, and the contribution to the nitrogen circular economy were examined. The results can serve as a reference for its developers to improve the technology from the environmental perspective