Removal of Ethanol from Indoor Air by Ficus elastica Roxb.: Process Optimisation and Post-Removal Desorption Dynamics

Indoor air pollution caused by volatile organic compounds (VOCs) is a major environmental and public health concern. Ethanol is a common indoor VOC released from cleaning products, disinfectants, and industrial activities. This study evaluated the capacity of Ficus elastica Roxb. to remove airborne ethanol under controlled chamber conditions. Response Surface Methodology was applied to optimise the effects of initial ethanol concentration, relative humidity, and exposure time on removal efficiency. The model predicted a maximum removal efficiency of 97.16%, which was experimentally validated with an average efficiency of 96.2%, confirming the model's reliability. Analysis of variance identified exposure time as the most influential factor affecting ethanol removal. Desorption experiments showed only limited and transient ethanol re-emission, indicating that ethanol was not merely adsorbed but also partially metabolised by the plant. Scanning electron microscopy revealed structural changes in stomatal morphology after prolonged exposure. Biochemical analyses demonstrated increased total phenolic content, flavonoid content, and antioxidant capacity, whereas a moderate decline in total chlorophyll reflected physiological stress accompanied by enhanced defence responses, indicating adaptive tolerance to prolonged ethanol exposure. These findings demonstrate the potential of F. elastica as an effective and sustainable botanical biofiltration system for improving indoor air quality.