Characteristics and Adsorption Test of Activated Carbon from Indonesian Bituminous Coal

The fast-growing batik industry in Indonesia raises the problem of the waste containing chromium. One method to remove chromium is by the adsorption process using activated carbon. Activated carbon can be made from coal. This commodity is a mining mineral the availability of which is still abundant in Indonesia. This study aimed to obtain: 1) the best concentration of activator and activation temperature in the manufacture of activated carbon; 2) characteristics of activated carbon (moisture content, volatile matter content, ash content, fixed carbon content, iodine number, specific surface area, pore-volume, pore surface area, pore radius, and SEM photos); 3) % activated carbon removal for chromium and maximum adsorption capacity for chromium; 4) Freundlich and Langmuir isotherm adsorption equation of activated carbon to chromium. The manufacture of activated carbon was carried out by a carbonization process followed by a chemical and physical activation processes. The chemical activator was ammonium phosphate with doses of 74.5 g/L, 149 g/L, 223.5 g/L, and 298 g/L. Meanwhile, physical activation was carried out at 848 K, 948 K, 1048 K, and 1148 K. The next step was to test the adsorption capacity of activated carbon on artificial batik waste containing chromium. The results showed that: 1) activator concentration did not significantly affect the characteristics of activated carbon. Meanwhile, the optimal activation temperature is at a temperature of 1048 K and 1148 K, which can produce the activated carbon that meets the requirements of activated carbon of the Indonesian National Standard 06-3730-1995 with the following contents: air content 0.16–0.81%; volatile matter 14.62–19.31%; ash 6.48–9.97%; fixed carbon 70.60–75.79%; iodine number 1243.13–1258.65%; specific surface area 31.930 m2/g; activated carbon pore volume 0.011 cc/g; pore surface area 8.905 m2/g; activated carbon pore radius 30.614; 3) the proportion of activated carbon removal for chromium is 37–53% and the maximum adsorption capacity for chromium is 52 mg/g; 4) the Freundlich equation test resulted in a constant R2 of 0.5126, n 2.4870, KF 8.8818 mg/g, while the Langmuir equation test resulted in a constant R2 of 0.8897, b -0.0075 L/mg, qm -90.0901 mg/g.