Fundamental photochemical approach to the concepts of fluence (UV dose) and electrical energy efficiency in photochemical degradation reactions

Abstract

For photochemical reactions in a quasi collimated beam, derivations are presented that introduce 'rate constants' based on the fluence (UV dose) received within the irradiated solution. These fluence-based 'rate constants' are shown to be fundamental and depend only on the quantum yield and the molar absorption coefficient at the irradiation wavelength. An experimental example is given, where the quantum yield for the photolysis of atrazine is determined to be 0.033. The new concepts are developed further to analyze the Figure-of-Merit Electrical Energy per Order (EEO), and it is shown that the EEO depends on the same fundamental photochemical parameters. An example of the photolysis of N-nitrosodimethylamine (NDMA) is presented, and it is shown that the EEO should decrease (increased electrical energy efficiency) as the radius of the UV reactor increases (increased path length), and should increase as the percent transmittance of the water decreases.