Investigation of effectiveness of pyrolysis products on removal of alizarin yellow GG from aqueous solution: a comparative study with commercial activated carbon.

The increasing use of dyestuff in industrial applications brings with it environmental problems. These dyes, which are an eco-toxic hazard, are common water pollutants, even at very low concentrations in water resources. Therefore, they must be removed in an economical way. In this study, low-cost biosorbents such as pine cone char, walnut shell char, and hazelnut shell char were prepared by pyrolysis process at different carbonization temperatures in the range of 400-700 °C. Biochars with the highest surface area were used to remove alizarin yellow GG from aqueous solution and the adsorption capacities of these materials were compared to commercially available activated carbon. Biomasses and prepared biochars were characterized using Fourier transform infrared spectroscopy, thermogravimetric/differential thermogravimetry analysis, Brunauer-Emmett-Teller (BET), scanning electron microscopy/energy dispersive X-ray spectroscopy, partial and elemental analysis techniques. Operational parameters such as contact time, temperature, pH, adsorbent dosage, and initial dye concentration were considered as variables for the batch adsorption experiments. Among the biochars used, the highest adsorption efficiency (82%) was obtained in pine cone char (BET surface area 259.74 m/g) at pH = 3, T = 45 °C, adsorbent dosage of 8 g/L, and initial dye concentration of 20 ppm. The adsorption mechanism has been investigated by applying different kinetic and isotherm models with the aid of time-dependent adsorption data. The adsorption process was best described by Langmuir isotherm and pseudo-second order kinetic model.