Removal of methylene blue by H3PO4Treated eucalyptus leaves: Study of fixed bed column and GA-ANN modeling

Abstract

This investigation aims to implement the fixed bed column method to eliminate methylene blue (MB) by H3PO4 treated eucalyptus leaves (PEUL). PEUL is characterized using SEM, XRD, FTIR, solid-state NMR, and BET surface areas. Initially, the batch experiments revealed that the maximum percentage removal of MB is obtained at pH 8. The column experiments are performed at pH 8 and 25 °C with a varying bed height (5–9 cm), rate of flow (10–20 ml min−1), and MB concentration (10–50 mg L−1). The column experimentation shows that the breakthrough and exhaustion times rise with the bed's height but decrease with the increasing rate of flow and MB concentration. Different well-known kinetic models are tested with the experimental results, which display that the Thomas model (R2 = 0.9969, χ2 = 0.0005) fits better than others, so it is appropriate for the scale-up design. The Langmuir isotherm model (R2 = 0.9949) is superior to the Freundlich model (R2 = 0.9516). The Langmuir maximum adsorption capacity is 52.18 mg g−1, which suggests monolayer adsorption. Desorption of MB from used adsorbents with CH3COOH solution (0.4 N) suggests 55.10% regeneration efficiency. The used adsorbents are safely disposable after incineration at 800 °C. This innovative study suggests that the inexpensive H3PO4 treated eucalyptus leaves feasible to use effectively for MB removal from the wastewater. The modeling using multiple linear regressions shows a statistically good result. The applicability of GA-ANN modeling is also tested.