High-efficiency adsorption for acid dyes over CeO2·xH2O synthesized by a facile method

Abstract

In this study, CeO2·xH2O with high-efficiency adsorption for acid dyes was synthesized via a facile method. Effect of temperature, pH and aging time in synthesis on the removal of acid red 14 (AR14) was investigated. It was found that the CeO2·xH2O prepared at 25 OC, pH of 4.5, and aged for 6 h is suitable for adsorption of AR14 and acid orange 7 (AO7) because of a large number of hydroxyl groups, NH4+ and oxygen vacancies in the resulting sample. The unary adsorption isotherm of AR14 on the optimized CeO2·xH2O adsorbent is well described by the Langmuir model, with an estimated adsorption capacity of 540 mg/g, which is a much higher value than those reported in literature. 100% of AR14 or 33% of AO7 in 40 ml of 250 mg/l aqueous solution can be removed by 0.02 g of the optimized CeO2·xH2O adsorbent. The CeO2·xH2O adsorbent also shows a good stability through several adsorption-regeneration cycles. Based on these excellent properties, the application in the removal of acid dyes from wastewater is anticipated. Furthermore, a novel adsorption mechanism was proposed based on the interaction between sulfonic groups (−SO3−) in acid dyes and protonated hydroxyl groups (−OH2+), ammonium radicals (NH4+), and oxygen vacancies (VO••) on the surface of the optimized CeO2·xH2O sample.