Preparation Of Co-doped K₂Nb₄O₁₁ And Its Photocatalytic Properties

Dye wastewater is an important source of harmful industry wastewater. The compositions of dye wastcwater are very complicate, toxic and mostly nonbiodegradable and also resistant to destruction by physico-chemical treatment methods. Photocatalytic oxidation technology is an attractive method for treating wastewater, which is of high efficiency, energy saving and non-second contamination. In this paper, K₂Nb₄O₁1 and Co-doped K₂Nb₄O₁1 were prepared by solid-phase reaction and their photocatalytic activities were evaluated by the photodegradation of acid red G on the catalysts.The results of X-ray diffraction (XRD) confirmed the crystal structure of K₂Nb₄O₁1 and Co-doped (10-15 wt%) K₂Nb₄O₁1 belong to tungsten-bronze (TB) type structure. CoNb₂O₆ was found in the Co-doped samples. The distribution of the particle sizes of K₂Nb₄O₁1 powders is form 500 to 800nm.The photocatalytic degradation results of acid red G by K₂Nb₄O₁1 and Co-doped K₂Nb₄O₁1 show that the photocatalytic activities of Co-doped (10-15 wt%) K₂Nb₄O₁1 are better than K₂Nb₄O₁1 When the concentration of acid red G solution was 50mg/L, the degradation of acid red G was 93% by K₂Nb₄O₁1 under UV irradiation for 120min, while 94.5% by Co-doped (10-15 wt%) K₂Nb₄O₁1. The composite effect of K₂Nb₄O₁1 and CoNb₂O₆ may play a major role on improving the photocatalytic activity of the obtained samples. Experimental results indicated that the prepared conditions of the catlayst such as calcining temperature, calcining time, dosages of catalyst, initial concentration of wastewater, pH value have great influences on the photocatalytic reactions. In this study, the catalysts prepared at 900℃ for 6h have higher photocatalytic activities. The optmum dosage of Co-doped (10-15 wt%) K₂Nb₄O₁1 for the photodegradation of acid red G of the concentration of 50mg/L is 1g/L. The higher color removal can be reached whether in acidic or alkalinous solution and the former was better than the latter. The kinetics of photocatalytic oxidation reaction for acid red G solution was studied in Co-doped K₂Nb₄O₁1 catalyst suspension phase, the results showed that the reaction belong to first-order and was coincident with Langmuir-Hinsheluwood (L-H) equation.The process of acid red G degradation was determined by UV-VIS and IR analyses. The mechanism of photocatalysis was discussed as well. The results showed that the decolouration of acid red G mainly owe to the photocatalytic degradation of Co-doped K₂Nb₄O₁1, but not to the adsorption on it.