Phenol adsorption onto orange peel biochar from aqueous solution: Isotherm study

In this study adsorption isotherms of orange peel biochar (Citrus sinesis) for removal of phenol from the aqueous solution were investigated. Orange peel biochar (OPB) having different particle sizes: 1, 3, and 5 mm (post pyrolysis) was produced at different pyrolysis temperatures i.e. 350, 450, and 550 ℃, (OPB350, OPB 450 and OPB550). Our Findings showed that surface chemistry of OPB varied greatly with pyrolysis temperature-rise in terms of aromatic functional groups and structural properties. Operating parameters i.e. adsorption reaction time (10-180 min), adsorbent dose (0.5-3 g) and phenol concentration (100-400 mg L-1) were studied. Our findinngs exhibited that phenol adsorption on biochar surfaces catalyzed at high pyrolysis temperature and particle size of 3 mm. Adsorption results indicate that the adsorption capacity of OPB reduced with high initial concentration and reached 98.3% with an increase in contact time (up to 120 minutes) afterward a declining trend was noted. It is evident from the findings of current investigation that OPB proved to be good adsorbent for phenol removal. The highest (98%) of phenol removal was observed at a lower initial concentration with OPB550 having 3 mm particle size whereas the minimal removal was noticed with OPB produced at lower pyrolysis temperature (OPB350) having 1 mm particle size. This is mainly attributed to less attachment sites on biochar surfaces and biochar particles become clogged. Adsorption isotherms followed Langmuir model with R2 values of 0.99, 0.992 and 0.987 for OPB350, OPB450 and, OPB550, respectively.