Wet oxidation

About: Wet oxidation is a research topic. Over the lifetime, 3094 publications have been published within this topic receiving 61536 citations.

Thermal wet oxidation improves anaerobic biodegradability of raw and digested biowaste.

Abstract: Anaerobic digestion of solid biowaste generally results in relatively low methane yields of 50−60% of the theoretical maximum. Increased methane recovery from organic waste would lead to reduced handling of digested solids, lower methane emissions to the environment, and higher green energy profits. The objective of this research was to enhance the anaerobic biodegradability and methane yields from different biowastes (food waste, yard waste, and digested biowaste already treated in a full-scale biogas plant (DRANCO, Belgium)) by assessing thermal wet oxidation. The biodegradability of the waste was evaluated by using biochemical methane potential assays and continuous 3-L methane reactors. Wet oxidation temperature and oxygen pressure (T, 185−220 °C; O2 pressure, 0−12 bar; t, 15 min) were varied for their effect on total methane yield and digestion kinetics of digested biowaste. Measured methane yields for raw yard waste, wet oxidized yard waste, raw food waste, and wet oxidized food waste were 345, 685, 536, and 571 mL of CH4/g of volatile suspended solids, respectively. Higher oxygen pressure during wet oxidation of digested biowaste considerably increased the total methane yield and digestion kinetics and permitted lignin utilization during a subsequent second digestion. The increase of the specific methane yield for the full-scale biogas plant by applying thermal wet oxidation was 35−40%, showing that there is still a considerable amount of methane that can be harvested from anaerobic digested biowaste.

Sodium hypochlorite oxidation reduces soil organic matter concentrations without affecting inorganic soil constituents

Abstract: Summary Oxidative treatment can isolate a stable organic matter pool in soils for process studies of organic matter stabilization. Wet oxidation methods using hydrogen peroxide are widely used for that purpose, but are said to modify poorly crystalline soil constituents. We investigated the effect of a modified NaOCl oxidation (pH 8) on the mineral composition of 12 subsoils (4.9–38.2 g organic C kg−1) containing varying amounts of poorly crystalline mineral phases, i.e. 1.1–20.5 g oxalate-extractable Fe kg−1, and of different phyllosilicate mineralogy. Post-oxidative changes in mineral composition were estimated by (i) the determination of elements released into the NaOCl solution, (ii) the difference in dithionite- and oxalate-extractable Si, Al and Fe, and (iii) the specific surface areas (SSAs) of the soils. The NaOCl procedure reduced the organic C concentrations by 12–72%. The amounts of elements released into the NaOCl extracts were small (≤ 0.14 g kg−1 for Si, ≤ 0.13 g kg−1 for Al, and ≤ 0.03 g kg−1 for Fe). The SSA data and the amounts of dithionite- and oxalate-extractable elements suggest that the NaOCl oxidation at pH 8 does not attack pedogenic oxides and hydroxides and only slightly dissolves Al from the poorly crystalline minerals. Therefore, we recommend NaOCl oxidation at pH 8 for the purpose of isolating a stable organic matter pool in soils for process studies of organic matter stabilization.

Biomass pretreatment with water and high-pressure oxygen. The wet-oxidation process

Abstract: A biomass pretreatment process called wet oxidation that utilized water, oxygen (240-480 psi), and temperatures above 120 degrees C was applied to loblolly pine, black oak, and a mixture of low-grade hardwoods. The process was found to be effective for fractionating the hemicellulose, lignin, and cellulose components of wood. Acid hydrolysis studies showed that the wet oxidation also enhanced the rate at which cellulose was hydrolyzed by acids to glucose. (Refs. 28).

The study of leachate treatment by using three advanced oxidation process based wet air oxidation

Abstract: Wet air oxidation is regarded as appropriate options for wastewater treatment with average organic compounds. The general purpose of this research is to determine the efficiency of three wet air oxidation methods, wet oxidation with hydrogen peroxide and absorption with activated carbon in removing organic matter and nitrogenous compounds from Isfahan's urban leachate. A leachate sample with the volume of 1.5 liters entered into a steel reactor with the volume of three liters and was put under a 10-bar pressure, at temperatures of 100, 200, and 300° as well as three retention times of 30, 60, and 90 minutes. The sample was placed at 18 stages of leachate storage ponds in Isfahan Compost Plant with the volume of 20 liters, using three WPO, WAO methods and a combination of WAO/GAC for leachate pre-treatment. Thirty percent of pure oxygen and hydrogen peroxide were applied as oxidation agents. The COD removal efficiency in WAO method is 7.8-33.3%, in BOD is 14.7-50.6%, the maximum removal percentage (efficiency) for NH4-N is 53.3% and for NO3-N is 56.4-73.9%. The removal efficiency of COD and BOD5 is 4.6%-34 and 24%-50 respectively in WPO method. Adding GAC to the reactor, the removal efficiency of all parameters was improved. The maximum removal efficiency was increased 48% for COD, 31%-43.6 for BOD5 by a combinational method, and the ratio of BOD5/COD was also increased to 90%. In this paper, WAO and WPO process was used for Leachate pre-treatment and WAO/GAC combinational process was applied for improving the organic matter removal and leachate treatment; it was also determined that the recent process is much more efficient in removing resistant organic matter.