Abstract
Gasifier Biochar (GBC) and Chitosan-Coated Gasifier Biochar (CGBC) derived from pine wood was used to remove Cu2+ and Cd2+ from water. Chitosan-Coated Gasifier Biochar was made by mixing GBC with aqueous acetic acid chitosan solution followed by treatment with NaOH. Both CGBC and GBC were characterized using FT-IR, scanning electron microscopy, surface area measurement (BET), elemental analysis, thermogravimetric analysis, and point of zero charge. Chitosan accounts for 25% of the weight of the CGBC. Thermogravimetric analysis showed chitosan decomposes sharply at 225–270°C and then more slowly thereafter. The BET surface areas of GBC and CGBC were 34.1 and 4.61 m2/g, respectively. Batch adsorption studies performed at pH values of 2–5 followed Cu2+ and Cd2+ adsorption quantitatively using atomic absorption spectrophotometry. Sorption was evaluated using the Freundlich, Langmuir, and Sips isotherm models. Cu2+ adsorption on CGBC fit best the Sips model (capacity 111.5 mg/g) and Cd2+ with the Langmuir model (capacity 85.8 mg/g). Langmuir adsorption capacities on GBC were 83.7 and 68.6 mg/g for Cu2+ and Cd2+ respectively. CGBC removed more Cu2+(25.8 mg/g) and Cd2+(17.2 mg/g) than GBC because chitosan modification generates amine coordination sites that enhance metal adsorption. Adsorption on CGBC and GBC of both metal ions followed pseudo-second order kinetics.
Highlights
Cadmium and copper ions are toxic and are a concern in the treatment of wastewaters (Fu and Wang, 2011)
Chitosan flakes, 3.0 g, from Dungeness Environmental was dissolved into 180 mL of 2% acetic acid
Coating with chitosan causes a dramatic decrease in the surface area of Coated Gasifier Biochar (CGBC) (4.61 m2/g). This decrease is due to the chitosan coating which covers pore openings and is consistent with previous studies (Zhou et al, 2013)
Summary
Cadmium and copper ions are toxic and are a concern in the treatment of wastewaters (Fu and Wang, 2011) These metals can enter the environment from metal plating facilities (Kadirvelu et al, 2001), mining operations (Razo et al, 2004), fertilizer plants (Sabiha et al, 2009), paper industries (Nriagu and Pacyna, 1988), batteries (Liu et al, 2014), and some preservatives and pesticides (Mohan et al, 2007). Copper is an essential nutrient, chronic high-level exposure can cause gastrointestinal distress and other health problems (Stern, 2010)
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