Regeneration of spent mercury catalyst for the treatment of dye wastewater by the microwave and ultrasonic spray-assisted method

Abstract

Abstract Large amounts of spent mercury catalyst (SMC) produced in producing polyvinyl chloride (PVC) has a great influence on the environment. In this work, microwave and ultrasonic spray were applied to regenerate the carrier of SMC. The optimal experimental conditions were the regeneration temperature of 900°C and regeneration time of 60 min. Subsequently, the textures of pores and mercury content, morphology structure and surface functional groups of SMC and the regenerated activated carbon (RAC) were characterized by N2 adsorption and desorption isotherms, ICP, SEM, EDS and FTIR. Additionally, the adsorption behaviors of RAC on methylene orange (MO) and congo red (CR) were explored to study the mechanisms. The results of kinetics and isotherm showed that experimental data were fitted well with the pseudo second-order and Langmuir isotherm model, respectively. The maximum adsorptions of MO and CR were 529 and 301 mg/g at 323 K. The thermodynamic results illustrated that the adsorption MO and CR onto RAC was spontaneous and endothermic. The results demonstrated that RAC prepared from SMC by microwave heating and ultrasonic spray could realize the comprehensive utilization of waste resources.