Short Communication Catalytic efficiency of copper oxide in degradation of phenol using sintered calcium phosphate (SCaP) as catalyst support S. Induja ⁎, P.S. Raghavan Department of Chemistry, Hindustan Institute of Technology and Science, padur, kelambakkam, Chennai-603103, India abstract article info Article history: Received 10 October 2012 Received in revised form 13 December 2012 Accepted 14 December 2012 Available online 23 December 2012 Keywords: Sintered calcium phosphate Catalyst support Phenol oxidation Copper catalyst For the first time sintered calcium phosphate is explored as catalyst–support, analogous to silica, alumina etc. The present work involves preparation of catalysts by depositing copper oxide over the sintered calcium phosphate using three techniques, viz., impregnation of CuO, impregnation of copper (II) nitrate & calcination, reduction of Cu 2+ ions on the support & calcination. The above samples were characterized using XRD, UV-DRS, SEM-EDAX, BET surface area and acidity. Oxidation of phenol was studied with the above catalysts and sintered calcium phosphate was found to be an efficient catalyst–support. © 2012 Elsevier B.V. All rights reserved. 1. Introduction Effluents from pharmaceutical industries, petrochemical refineries, resin manufacturers, etc., contain phenolic pollutants [1–4]. Methods like biological, chemical oxidation, photo-catalysis, etc., are used for deg- radation of phenol. Among these methods, the wet catalytic oxidation with hydrogen peroxide is a well established process [5]. Few studies with transition metal oxides such as copper oxide are effective in catalytic degradation of phenol [6–8] using conventional catalyst–supports like silica, alumina, zeolites, etc. Invariably, low concentrations of phenol in the reaction mixture were used to study the efficiency of the above cata- lysts. Exploration of a non-conventional catalyst–support that would degrade higher concentrations of phenol lead to the idea of using sintered calcium phosphate (SCaP) as a catalyst support [9]. The SCaP has P–O–P chains containing terminal P–O–H groups cross-linked by calcium ions [10] and hence, it is expected to be acidic in nature. 2. Experimental Preparation of SCaP involved mixing calcium carbonate (precipitated, 99%) with distilled water to form a paste and adding phosphoric acid (Merck-India, 85%) in drops under continuous stirring. The mixture was transferred to an alumina crucible and dried at 150 °C for 8 h, followed by sintering at temperatures between 600 °C and 900 °C in a muffle fur- nace under static-air atmosphere. The resultant powder was crushed and sieved through 325 mesh. This sieved powder was suspended in copper nitrate solution (Merck-India, >99%) under stirring. Calculated quanti- ty of base (sodium hydroxide-Merck-India, 97% or Ammonia solution- Qualigens, 25%) was added till the pH of the mixture reached 8 and hy- drazine hydrate (SD Fine chemicals, 80%) was added drop-wise. The precipitate formed was filtered through G4 sintered crucible and dried in hot-air oven followed by calcination at 400 °C for 30 min. The cata- lyst was labeled as Cu/SCaP-DRC. The procedure was repeated using silica as support (BAM, 20 μm, 99.5%). The details of the catalysts pre- pared and their respective identification code is given in Table 1. The impregnated catalyst was prepared by mixing CuO (Merck-India, 99%) with the support using iso-propyl alcohol (SD Fine chemicals, 99%) and dried in hot-air oven for 2 h followed by calcination at 400 °C for 30 min. The catalyst was labeled as CuO/SCaP. The third method involved dissolving copper nitrate in distilled water and making paste with catalyst–support. It was then evaporated in a hot-water bath and dried in hot-air oven for 2 h followed by calcination at 400 °C for 30 min. The catalyst was labeled as Cu/NO 3 /SCaP. Powder X-ray diffraction data for the samples were collected on a GE Analytical XRD (XRD 3003 T/T). The SEM-EDAX analysis was carried out using a Quanta Field Emission SEM (Quanta-200F). The surface area was measured using Micromeritics ASAP 2020/USA. UV–visible spectra were recorded using PerkinElmer spectrometer (LAMBDA-850 UV–Visible Spectrophotometer), in reflectance mode. Acidity of the catalysts was measured using adsorption of n-butyl amine (SD Fine chemicals, 98%) as per the procedure reported in litera- ture [11]. Oxidation of phenol was carried out using batch-type reactor. Phenol was dissolved in water containing hydrogen peroxide and stirred at 300 rpm. Catalyst was introduced into the reaction mixture and prog- ress of the reaction was monitored by analyzing the decrease in phenol content using spectroscopic method as explained in literature [12]. Catalysis Communications 33 (2013) 7–10 ⁎ Corresponding author. Tel.: +91 44 27474262; fax: +91 44 27474208. E-mail address: sinduja@hindustanuniv.ac.in (S. Induja). 1566-7367/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.catcom.2012.12.016 Contents lists available at SciVerse ScienceDirect Catalysis Communications journal homepage: www.elsevier.com/locate/catcom