title: Sulfate radical-advanced oxidation process (SR-AOP) for simultaneous removal of refractory organic contaminants and ammonia in landfill leachate.
abstract: Typically, a mature landfill leachate contains high levels of non-biodegradable organics and ammonia nitrogen. Simultaneous removal of the both persistent leachate pollutants is a significant challenge. This paper reports the first scientific study to apply a sulfate radical (SO(4)(·-)) - based advanced oxidation process (SR-AOP) to treat a mature leachate, with an emphasis of concurrent removal of refractory organics and ammonia. In this study, all the experiments were run in a batch reactor with temperature control. In the thermal persulfate oxidation (TPO) process, persulfate (S(2)O(8)(2-)) was activated by heat to produce powerful oxidants, SO(4)(·-) (E(o) = 2.6 V). Three factors affecting the removal efficiencies of chemical oxygen demand (COD) and ammonia nitrogen were investigated, including initial solution pH (3-8.3), temperature (27-50 °C), and chemical dose (S(2)O(8)(2-):12COD(0) = 0.25-2.0). Typically, acidic pH (3-4), higher temperature, and higher dose favored the removal of COD and ammonia. At S(2)O(8)(2-):12COD(0) = 2 and 50 °C, the COD removal rates were 79% and 91% at pH 8.3 (no pH adjustment) and 4, respectively; and the ammonia nitrogen removal reached 100% at pH 8.3 or 4. SR-AOP appears to be more advantageous over hydroxyl radical (OH∙)-based advanced oxidation processes (HR-AOPs) because OH∙ almost does not oxidize ammonia. Furthermore, compared with Fenton treatment of the same batch leachate sample, the TPO could achieve a higher COD removal at an identical chemical dose. For example, COD removal was 40% at H(2)O(2):2.125COD(0) = 2 during Fenton treatment (pH 3), but 91% at S(2)O(8)(2-):12COD(0) = 2 during TPO (pH 4). These findings demonstrate that SR-AOP is a promising landfill leachate treatment method.
authors.affiliation: Department of Earth and Environmental Studies, Montclair State University, Mallory Hall 252, 1 Normal Ave, Montclair, NJ 07043, USA. dengy@mail.montclair.edu
authors.forename: Yang
authors.initials: Y
authors.lastname: Deng
authors.forename: Casey M
authors.initials: CM
authors.lastname: Ezyske
mesh_terms: D000641:Ammonia / Q000302:isolation & purification*; D057919:Biological Oxygen Demand Analysis; D006863:Hydrogen-Ion Concentration; D009584:Nitrogen / Q000302:isolation & purification; D009930:Organic Chemicals / Q000302:isolation & purification*; D010084:Oxidation-Reduction; D013431:Sulfates / Q000737:chemistry*; D013696:Temperature; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D018508:Water Purification / Q000379:methods*
chemical_list: D009930:Organic Chemicals; D013431:Sulfates; D014874:Water Pollutants, Chemical; C069025:sulfate radical; D000641:Ammonia; D009584:Nitrogen