The immobilization of sedimentary phosphorus (P) by capping sediments with amended calcium peroxide material (ACPM) and CaO 2 was investigated, the sediments and overlying water from a black-odor river. Under the capping with ACPM and CaO 2 , the pH and dissolved oxygen (DO) in the overlying water were higher than in the control. This contributed to the more loss of external P under the ACPM (the phosphate sorption was fitted well by the Langmuir equation, the maximum P sorption capacity up to 29.28 mg P g −1 ). Additionally, ACPM improves the decrease of the reduction materials (e.g., NH 4 + -N, Fe 2+ ) in the pore water compared to that associated with CaO 2 , resulting in a less obvious dissolved inorganic P (DIP) in the pore water, but the accumulation of DIP in the pore water with CaO 2 suggested an explosive release once the micro-environment conditions encounters adverse conditions. The sharp reduction of Fe/Al-P and Res-P contributes to the increase of DIP in the pore water, with a release of up to 390.60 mg P kg −1 DW (dry weight), whereas the value is only 62.55 mg P kg −1 DW when capped with ACPM. Correspondingly, the percentage of the bioavailable P to Tot-P decreases rapidly from 17.27% (control, 0–2 cm) to 7.21% (ACPM, 0–2 cm) and 10.57% (CaO 2 , 0–2 cm), indicating the obvious P immobilization. The implication is that the application of CaO 2 is not suitable for direct use, while the combination with other materials (e.g., WPS) is a better choice.
Xudong Bu,Yurong Zhang,Haiqing Guo,Sheng Wang,Xueyan Du
The ion removal capacity of carbon based capacitive deionization (CDI) is limited by the double-layer mechanism. Replacing one electrode of the conventional carbon-based symmetric CDI with a battery-like ion insertion material to obtain hybrid capacitive deionization (HCDI) can significantly improve the adsorption capacity . Various ion insertion materials have been adopted for HCDI, however, how to optimize the performance of the HCDI system by matching the two electrodes with different ions removal mechanism remains challenging. In this work, a HCDI desalination cell was demonstrated by using NaTi 2 (PO 4 ) 3 /reduced graphene oxide composites (NTP-rGO-700) as the cathode and activated carbon (AC) as the anode. Based on the mass balance strategy of electrodes and the electrochemical behavior of hybrid capacitors with different AC:NTP-rGO-700 mass ratios, the HCDI desalination cell was assembled with the optimal AC:NTP-rGO-700 mass ratio of 2:1. At an operating voltage of 1.6 V and a current density of 125 mA·g −1 , the specific adsorption capacity (SAC) of the HCDI cell can reach 51 mg·g −1 with an average salt adsorption rate (ASAR) of 2 mg·g −1 ·min −1 , and the energy consumption (E m ) is 136.53 kJ·mol −1 . This work provides an efficient approach for developing high performance HCDI cell.
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