Search

Benzoic acid can affect the iron-oxide mineral dissolution and react with hydroxyl radical. This study investigated its effect on 1,2-dichloroethane removal process by siderite-catalyzed hydrogen peroxide and persulfate. The variation of benzoic acid concentrations can affect pH value and soluble iron concentrations; when benzoic acid varied from 0 to 0.5 mmol/L, pH increased while Fe and Fe concentrations decreased, resulting in 1,2-dichloroethane removal efficiency which decreased from 91.2 to 5.0 %. However, when benzoic acid varied from 0.5 to 10 mmol/L, pH decreased while Fe and Fe concentrations increased, resulting in 1,2-dichloroethane removal efficiency which increased from 5.0 to 83.4 %. [ABSTRACT FROM AUTHOR]

A novel sequential permeable reactive barrier (multibarrier), composed of oxygen-releasing compound (ORC)/clinoptilolite/spongy iron zones in series, was proposed for ammonium-nitrogen-contaminated groundwater remediation. Column experiments were performed to: (1) evaluate the overall NH-N removal performance of the proposed multibarrier, (2) investigate nitrogen transformation in the three zones, (3) determine the reaction front progress, and (4) explore cleanup mechanisms for inorganic nitrogens. The results showed that NH-N percent removal by the multibarrier increased up to 90.43 % after 21 pore volumes (PVs) at the influent dissolved oxygen of 0.68∼2.45 mg/L and pH of 6.76∼7.42. NH-N of 4.06∼10.49 mg/L was depleted and NO-N (i.e., NO-N + NO-N) of 4.26∼9.63 mg/L was formed before 98 PVs in the ORC zone. NH-N of ≤4.76 mg/L was eliminated in the clinoptilolite zone. NO-N of 10.44∼12.80 mg/L was lost before 21 PVs in the spongy iron zone. The clinoptilolite zone length should be reduced to 30 cm. Microbial nitrification played a dominant role in NH-N removal in the ORC zone. Ion exchange was majorly responsible for NH-N elimination in the clinoptilolite zone. Chemical reduction and hydrogenotrophic denitrification both contributed to NO-N transformation, but the chemical reduction capacity decreased after 21 PVs in the spongy iron. [ABSTRACT FROM AUTHOR]