Arsenic removal from water and river water by the combined adsorption - UF membrane process

Abstract

In this study, a pilot-scale adsorption-UF process equipped with an aerated system is established for arsenic removal from As-spiked Songhua river water. A newly synthesized amino-functionalized coffee cellulose adsorbent (PEI-coffee) which is derived from spent coffee powder is fully characterized and used for arsenic removal from water. The batch experiments revealed that the adsorption process could be well described by Langmuir model with a maximum adsorption capacity of 13.2 and 46.1 mg/g for As(III) and As(V), respectively. The negative value of △H and △G indicated the exothermic and spontaneous nature of As adsorption on PEI-coffee. The effects of operating parameters such as pH, initial concentration and adsorbent dosage, were optimized by response surface methodology (RSM) based on a central composite design (CCD). The combined adsorption - UF process was employed for arsenic removal from As-spiked Songhua river water. It was demonstrated that aeration not only increased the removal efficiency by oxidizing As(III) to As(V), but mitigated the membrane fouling process. Besides of the adsorption process, UF membrane could also reject arsenic through the electrostatic repulsion between arsenic species and membrane surface. After UF filtration, the dissolved As, suspended solids (SS), and TOC can be effectively eliminated. The saturated adsorbent was regenerated by using an eluting agent of 10 wt% NaCl and 10 wt% NaOH, the regenerated adsorbent still sustained a very high adsorption capacity after 6 cycles of adsorption-regeneration process.

Keywords: Adsorption; Arsenic; Cellulose; Membrane; River water.