Chemical Regeneration of Activated Carbon Used in A Water Treatment System for Medical Services

Abstract

The chemical regeneration of exhausted granular activated carbon (GAC) from a water treatment plant to produce dialysis water used in hemodialysis treatments for chronic renal disease patients from a general Hospital of Ciego de Avila province, Cuba, was investigated. Activated carbon (AC) exhausted mainly by inorganics (Ca (Ca-chelates), Mg and Na) was regenerated using hydrochloric acid and acetic acid (one regeneration cycle). Solutions of 5%, 10%, 15% and 20%(v/v) as well as four contact times (2 h, 4 h, 6 h and 48 h) for hydrochloric acid and three contact times (2 h, 4 h and 6 h) for acetic acid at 25°C and 1 atm in a dosage of 1 g GAC/10 mL were used. Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES), thermogravimetric analysis (TGA), X-ray absorption technique (XRA) and Scanning Electronic Microscopy (SEM) were used to evaluate the effect of the regeneration on exhausted GAC. Batch and scaled column experiments were developed. Breakthrough curves were obtained to assess the AC’s performances after chemical regeneration. The removal/adsorption capacity towards free chlorine (as disinfection agent) and hardness ions (expressed in mg CaCO₃/L) was estimated using the area under the breakthrough curves from scaled columns experiments. The hydrochloric acid arises as the best acidic regenerator; using a concentration of 20%(v/v), regenerated GACs using hydrochloric acid showed the highest desorption rate of inorganics as well as a free chlorine removal performance of around 30% concerning the virgin GAC sample. A new GAC management scheme is proposed for GACs used in the medical industry to improve the sustainability and economics of the water treatment process.