Photocatalytic degradation of an organic dye in some aqueous buffer solutions using nano titanium dioxide. A kinetic study

Abstract

Photocatalytic degradation of an organic dye, emerald green, on nano titanium dioxide (anatase 99.5%) at basic buffer pH of 7, 8 and 9 has been investigated. The effects of various operating parameters such as initial concentration of dye, catalyst dosage, bufferic pH and irradiation time on photocatalytic degradation have been studied in a photoreactor cell containing high pressure mercury lamp to obtain the optimum conditions. COD removal was found to be 65-71% confirming considerable mineralization. The photodegradation of the dye obeyed a pseudo-first order kinetics according to the Langmuir-Hinshelwood model at all used buffer pH. The observed rate constants (k obs) of photocatalytic degradation were 3.3 × 10-2 min-1 , 7.09 × 10-2 min-1 and 1.32 × 10-1 min-1 at buffer pH of 7-9 respectively. Furthermore, the Langmuir-Hinshelwood rate constants, k r and adsorption constants, K A are reported for current process at various buffer pH.

Fotocatálisis heterogénea para el tratamiento de aguas residuales generadas en el baño del ganado

“…Otros estudios también demuestran que la degradación de plaguicidas como la cipermetrina mediante fotocatálisis heterogénea usando TiO 2 , se ve favorecida a un pH ácido (Yao et al, 2007; Affam y Chaudhuri, 2013), bajo ciertas condiciones de pH las sustancias orgánicas pueden disociarse y adquirir una carga neta negativa, favoreciendo su adsorción hacia la superficie del catalizador cargada positivamente bajo estas condiciones (Valencia et al, 2011;Gao et al, 2011;Vineetha et al, 2013). (Son et al, 2009;Khan et al, 2010;Sahoo et al, 2012;Montazerozohori et al, 2012;Zhao et al, 2014;da Silva et al, 2015 Las constantes de velocidad aparente k app fueron 0,0066 min -1 para radiación UV alta, y 0,0034 min -1 para radiación UV baja, indicando una mayor tasa de degradación durante los días soleados que durante días nublados. Lo anterior se explica debido a que durante los ensayos realizados con radicación UV acumulada baja aproximadamente un 50 % de los fotones UV disponibles en la radiación solar se encuentran en el componente difuso (Giménez et al, 1999)…”

Sonophotocatalytic treatment of diazinon using visible light‐driven Ce:Cu‐1,4‐BDOAH2 photocatalyst in a batch‐mode process: Response surface methodology and optimization

“…The most common kinetic model for degradation processes is the Langmuir–Hinshelwood (L‐H) model which is accepted for degradation of dyes, pesticides and many organic compounds. The sonophotocatalytic degradation of diazinon obeys pseudo‐first‐order kinetics based on the L‐H model as follows: where C is the diazinon concentration and k (min −1 ) is the apparent rate constant. Integration of equation leads to a concentration–time equation as follows: …”

Impact of the water composition on the degradation kinetics of natural organic matter in photocatalytic membrane reactors

“…The rate of reaction of degradation (r) has been determined based on the Langmuir-Hinshelwood (L-H) model. It is directly proportional to the rate of surface cover with organic substrate (Θ x ) [2,16,17] according to the equation:…”