An efficient bio-adsorbent for the removal of dye: Adsorption studies and cold atmospheric plasma regeneration

Abstract

Modifying agricultural biomass to make effective and economic adsorbents as well as regeneration of the exhausted ones has long been researched in wastewater treatment. The aim of this study was modifying waste tea (WT), a common agricultural by-product, with citric acid (CA) in a mild way to produce potential adsorbents for methylene blue (MB), and regenerating the spent adsorbents by cold atmospheric plasma (CAP) at normal temperature and pressure. Batch adsorption experiments were performed to investigate the effects of CA modified waste tea (CA–WT) on MB adsorption. Results revealed that CA modification effectively contributed to MB removal. MB adsorption on CA–WT was well described by the Langmuir isotherm model, and the maximum MB adsorption capacity of CA–WT was 212.77 mg/g at 298 K. After adsorption, the spent CA–WT was regenerated by cold atmospheric plasma (CAP). With the adsorption–regeneration cycle repeated six times, the CA–WT regeneration efficiency (RE) remained at a very high level. The technique presented in this study has an optimistic outlook for practical application in adsorbent modification and regeneration.