Evaluating the Removal of Hexavalent Chromium (Cr -VI) in Wastewater by Low-Cost Adsorbent Modified from Waste Fly Ash

Abstract

The Cr (VI) is a toxic element to human and other organisms. In this paper, the adsorption of Cr (VI) to fly ash zeolite (FAZ) was investigated in batch modes. The effect of pH (2 – 9), initial Cr (VI) concentration (0.2 – 1.4 mg/L), adsorbent amount (0.01 – 3.00 g), and contact time (0 – 5 h) was investigated. These experiments were carried out in an Erlenmeyer flask containing 50 mL solution of Cr (VI) at room temperature. The Langmuir and Freundlich models were applied for determining the adsorption characteristic and isotherms. The FAZ was tested for removing Cr (VI) containing in actual metal plating industry effluent. The result showed that in the investigated values of pH the adsorption ability decreased when pH increased. The adsorbent dose of FAZ provided the best capacity at 0.05g FAZ in 50 mL solution; the suitable adsorption time was observed at 3 h duration; the 0.8 mg/L of Cr (VI) concentration was appropriated in this study. The Langmuir model was matched to the experimental records (R2 = 0.9922) which demonstrated that the Cr (VI) adsorption on FAZ belonged to monolayer type. In order reach the standard regulation at the column B, QCVN 40:2011/BTNMT for effluent industrial wastewater (Cr (VI) concentration is under 0.1 mg/L), it took 6 h duration for the adsorption to drop the initial Cr (VI) concentration of 0.803 mg/L to 0.091 mg/L. It can be suggested that FAZ is a good material for treating of Cr (VI) in aqueous solution and industrial wastewater.