Optimization study for chemical activation of biochar derived from sugarcane bagasse for maximum phytohormone adsorption from waste coconut water

Abstract Improper treatment and disposal of sugarcane bagasse (SB) in farms and sugar industries can lead to environmental and health concerns. Instead of burning these wastes, bagasse can be utilized for biochar production which can be applied as adsorbents. Additionally, studies reported that the performance of biochar adsorbents can be improved by activation. Hence, this study aimed to optimize the chemical activation conditions of biochar from SB for maximum adsorption of phytohormones from waste coconut water (WCW). Pretreated SB was first converted into biochar though pyrolysis and was chemically activated using potassium hydroxide (KOH). Response Surface Methodology was used to determine the optimum activation conditions to maximize phytohormone adsorption efficiency. Factors considered were KOH-biochar ratio (1:1 to 5:1 g/g) and carbonization holding time (45 to 90 minutes). Analysis of Variance showed that the adsorption efficiency of activated biochar is significantly affected by KOH-biochar ratio. Increasing the ratio created cavities on the surface which serve as adsorption sites; however, further increase in ratio resulted in pore degradation lowering the adsorption performance of activated biochar. Conversely, carbonization holding time did not have significant effect on the response for the range of factors considered. The optimum conditions which were 3.18:1 KOH-biochar ratio and 65.64 minutes holding time resulted to ~82.14% actual phytohormone adsorption efficiency. The characteristics of the optimized activated biochar (SBAB) were then compared with that of the unmodified biochar (SBB) in terms of morphology, surface elemental composition, functional groups, adsorption efficiency, average particle size, and bulk density. The SBAB produced can be applied in further studies focusing on the adsorption of phytohormones from WCW and desorption from the adsorbent to isolate them. Results of this study can also provide a sustainable solution in minimizing the disposal of sugarcane bagasse and waste coconut water while increasing their economic returns and environmental benefits.