Application of calcium-rich mineral under nonwoven fabric mats and sand armor as cap layer for interrupting N and P release from river sediments

Abstract

This work investigates the applicability of thermally treated calcium-rich clay minerals (CRCMs), such as sepiolite (SPL), attapulgite (ATT), and dolomite (DLM) to hinder the nitrogen (N) and phosphorus (P) release from river sediments. A non-woven fabric mat (NWFM) or a sand layer were also capped as armor layers, i.e., placed over CRCMs to investigate the capping impact on the N/P release. The capping e ciency was evaluated in a cylindrical reactor, consisting of CRCMs, armor layers, sediments, and sampled water. We monitored N/P concentrations, dissolved oxygen (DO), oxidation reduction potential, pH, and electric conductivity in overlying water over 70 days. The DO concentrations in the uncapped and capped conditions were preserved for 30 days and 70 days (until the end of experiment duration), respectively. ATT showed higher e ciency for NH 4 -N and T-N than the other two materials, and the capping e ciency of NH 4 -N was measured as 96.4%, 93.7%, and 61.6% when capped with 2 cm sand layer, 1 cm sand layer, and NWFM layer, respectively. DLM showed a superior rejection capability of PO 4 -P to ATT and SPL, reported as 97.2% when capped with 2 cm sand armor. The content of weakly adsorbed-P was lower in the uncapped condition than in the capping condition. It can be concluded that ATT and DLM can be used as capping agents to deactivate N and P, respectively, to reduce water contamination from sediments of the eutrophic river.

Application of Activated Seashells and Sand Armor for Disrupting N and P Release from River Sediments

“…Higher NH 4 -N concentrations were observed for MS/SA0 and MS/SA1 than that for NAC/SA0 (untreated), indicating that MS/SA0 and MS/SA1 capping accelerated NH 4 -N release from sediments to overlying water rather than disrupting NH 4 -N release. The acceleration of the NH 4 -N releases by MS/SA0 and MS/SA1 was attributed to the Ca 2+ and Mg 2+ ions eluted from the MS-released NH 4 -N adsorbed on the surface of the sediments via ion exchange [60]. The much higher EC values of MS/SA0 and MS/SA1 (Figure 2c) were also consistent with the large number of ions eluted from the MS capping material to the overlying water, affecting the release of NH 4 -N from sediments.…”

Valorization of Fenton sludge by pyrolysis as a green adsorbent for arsenate removal

“…The increased amount of Ca leaching from FS-BC at higher pyrolysis temperatures is in line with their higher pH (Table 1), given that calcium is considered a base cation. 37,38 Figure 2(a)-(f) shows the XRD pattern of FS-BC, indicating its crystalline structure. Peaks associated with iron were detected in the FS-BC XRD pattern.…”