DEGRADATION STUDIES OF METHYLDIETHANOLAMINE BY USING UV/H202 ADVANCED OXIDATION PROCESS

Methyldiethanolamine (MDEA) in aqueous solutions is frequently used for
scrubbing carbon dioxide (C02) and hydrogen sulfide (HzS) from natural gas. Large
quantity of MDEA disposed into the wastewater during cleaning and maintenance as
well as shutdown of the absorption and desorption columns of the gas processing
plant. The MDEA is not readily biodegradable and such wastewater cannot be treated
using the conventional treatment facility. Advanced Oxidation Processes (AOP's),
such as oxidation by Fenton's reagent, UV/Hz02 and UV/Ozone have been
recommended as a class of techniques used for the total/partial degradation of
recalcitrant organics which are not readily amenable to conventional biological
oxidation. Based on the advantages of UV/H20z process such as no formation of
sludge during the treatment, applicable for a wide range of pH, and high capability of
hydroxyl radical production, the UV /H20 2 process was chosen for the treatment of
effluents containing MDEA from refinery plant. For this purpose, a synthetic MDEA
solution and a real effluent from gas processing unit of a refinery were used for the
experiments employing UV/H20 2 advanced oxidation process. The degradation of
MDEA was found to be highly dependent on the initial concentration of H20 2, the
initial pH, and the reaction temperature. The important parameters that govern the
MDEA degradation by UV/Hz02 process were optimized using response surface
methodology (RSM). The optimum conditions for degradation process of synthetic
MDEA waste were at initial pH = 9.76, ratio between contaminant to
oxidant = 1000 ppm of organic carbon to 0.22 M H20 2 , and temperature = 30°C.
Whilst the optimum condition of degradation process of real refinery effluent was at
initial pH= 8.13, ratio between contaminant to oxidant= 1000 ppm organic carbon to
0.24 M of H20 2 , and temperature= 30°C.