Photocatalytic decomposition of p-nitrophenol over titanium dioxides prepared in water-in-carbon dioxide microemulsion

Ceramic Membranes Photocatalytically Functionalized on the Permeate Side and Their Application to Water Treatment

This work deals with direct coupling of membrane separation and photocatalytic degradation by using photocatalytic ceramic membranes. An unusual configuration is considered here, with the irradiation applied on the permeate side of the membrane in order to mineralize small organic molecules not retained by the membrane. Different types of such membranes are presented. Their functional performance is quantified thanks to a simple experimental method enabling the estimation of the specific degradation rate δ, i.e., the quantity of destroyed organic molecules per unit of time and of membrane surface area. The relevance of δ for the design and scale-up of purification units is then illustrated. Finally, current technological challenges and potential solutions concerning the industrial implementation of such photocatalytic membranes are discussed.

Intensification of sonophotocatalytic degradation of p-nitrophenol at pilot scale capacity

Sonophotocatalysis involves the use of a combination of ultrasonic irradiation, ultraviolet radiation and a semiconductor photocatalyst, which enhances the rates of chemical reactions by the formation of enhanced amounts of free radicals. In the present work, the sonophotocatalytic degradation of p-nitrophenol has been investigated using low frequency ultrasound waves (25 kHz) with an acoustic power of 1 kW and UV tube of 11 W power rating at an operating volume of 7 L. The efficacy of combination of sonochemistry and photocatalysis has been initially compared with the individual operation of sonolysis and photocatalytic oxidation. The effect of operational conditions such as the initial p-nitrophenol concentration, pH and catalyst concentration on the extent of degradation has been investigated using sonophotocatalysis. The initial concentration of the pollutant was varied in the range 10 to 100 ppm whereas pH in the range of 2.5-11 and catalyst loading in the range of 0.5-4 g/l. Intensification studies have been carried out using hydrogen peroxide and Fenton chemistry. In all the systems investigated, maximum extent of degradation (94.6%) was observed for 10 ppm of p-nitrophenol initial concentration (w/v) using combination of sonophotocatalysis and optimum quantity of H(2)O(2). Use of Fenton chemistry also plays an effective role in enhancing the extent of degradation though the concentration of additive needs to be carefully adjusted in order to get maximum beneficial effects.

High efficiency degradation of 4-nitrophenol by microwave-enhanced catalytic method

Application of the microwave-enhanced catalytic degradation (MECD) method on the abatement of 4-nitrophenol (4-NP) using nickel oxide was studied. A mix-valenced nickel oxide was prepared from nickel nitrate aqueous solution through a precipitation with sodium hydroxide and an oxidation by sodium hypochlorite with/without microwave-assisted heating. They were characterized by X-ray (XRD), infrared spectroscopy (IR), temperature programmed reduction (TPR), and transmission electron micrographs (TEM). Their catalytic activities towards the degradation of 4-NP were investigated through continuous bubbling of air during the liquid phase and evaluated quantitatively with high pressure liquid chromatography (HPLC). Also, the effect of the kinds of catalyst, temperature, pH, initial concentration, and dosage of catalyst on the efficiency of 4-NP degradation was investigated. The results showed that the 4-NP was completely degraded using the high efficiency MECD method within 15 min under [H(+)] = 1.0M, T = 40 °C, and C = 200 ppm over nickel oxide.