Kỷ yếu Hội nghị: Nghiên cứu cơ bản trong “Khoa học Trái đất và Môi trường” DOI: 10.15625/vap.2019.000215 602 STUDY OF BIOCHAR FROM GRO-WASTE FOR DYE ADSORPTION: CAPACITY AND KINETICS Nguyen Xuan Cuong 1* , Tran Thi Cuc Phuong 2 , Vo Thi Yen Binh 2 1 Center for Advanced Chemistry, Institute of Research and Development, Duy Tan University 2 Faculty of Environmental Engineering Technology, Hue University, Quang Tri Campus, Viet Nam Email: nguyencuongqt2008@gmail.com ABSTRACT Two biochars derived from wattle bark (BA) and coffee husks (BC) used to remove methylene blue (MB) which achieved the yield values of 33.3 % to 35.08% at 500 o C of pyrolysis. Adsorption increased with the rising of the dose until 2 g/L for BC, and 5 g/L for BA, respectively. When rising pH, the increasing trend was observed for BA, and BC, from 67 % at pH of 2 to 93% at pH of 12. The equilibrium time depended on the initial MB concentration and the MB removal accounted for over 83% at the first 30 minutes. The experiment data fits better with Avrami, and Elovich than Pseudo-first-order equation (PSO), and Pseudo-second-order model (PFO). Adsorption process comprised more than one reaction pathway including integer-kinetic order, and multiple kinetic orders or fractionary kinetic order. 1. INTRODUCTION Dyes cause primarily to colored compounds in water (Hao et al., 2000; Santos & Boaventura, 2015), in which azo dyes like MB is being used extensively (Hao et al., 2000; Tan et al., 2016). To treat these dyes, many methods have been introducing such as coagulation, advanced oxygen process, membrane, and adsorption (Hao et al., 2000; Park et al., 2019). However, many of them are expensive, high energy consumption and toxic secondary generation. Biochar - a low cost carbonaceous material to eliminate contaminants, has attracted much attention. In general, the studies of biochar for dye removal and decolorization have achieved significant results. Moreover, biochars produced from agro-waste bring other benefits in terms of waste minimization, recovery and reuse, and environmental conservation. The focus of this work is to compare the adsorption capacity of biochars derived from wattle bark, and coffee husks for MB removal and to clarify the adsorption kinetics. These materials using to produce biochars in this study are not yet investigated for dye removal. 2. MATERIALS AND METHODS 2.1. Raw materials The wattle bark and the coffee husks collected from local processing factories. MB is an organic cation dye which chosen to test adsorption potential of biochars. 2.2. Biochar production Fig.1. Raw materials, biochars and SEM images at 10 μm.