Preparation of Graphite from Bamboo (Yashininia alpine) and its Application for Fluoride Ion Removal in Water Treatment

Abstract

People in several regions of the Rift Valley of Ethiopia are consuming much higherfluoride ion concentrations beyond WHO recommended level, which has resulted in both dental and skeletal fluorosis.Under this study,an average of the five selected boreholeswater samples (11.72mg/L) around Adama was taken to prepare synthetic fluoride water. Low cost and easily available lignocellulosic biomass, bamboo,was used as a precursor for graphite preparation and application on fluoride removal.Activated raw bamboo was calcined at different temperatures of {400 and 600°C} and biochar was activated using two different catalysts {Al andFeCl3.6H2O}. Method of heat treatment was used for graphitization, andthe catalyst impregnated biochar was graphitized at different temperatures {800, 900 and 1000°C} and at different graphitization times {1.5, 2.5 and 3.5 hr} in muffle furnace.Those parameter effects were studied using XRD and FTIR instruments and X’pert Software. An obvious Graphite reflection peak was detected and confirmed by diffraction peaks at 26.65° and around 44°. Better graphitization with increasing temperature was confirmed using X’pert softwareand FTIR as graphite diffraction pattern and skeleton of graphite structure was formed. The experiments were conducted on batch adsorption test at conditions of adsorbent dosage {0.5, 1, 1.5 and 2 g}, particle size of {250-355, 355-500 and 500-7010µm} and contact time of {30, 60, 90 and 120 min}. The maximum adsorption efficiency (48.70%) was obtained at an adsorbent dose of 2g, the particle size of 250- 355µm and 2hr contact time. In this research, fluoride removal on bamboo driven graphite samples {G-FeCl3.6H2O1000°Cand G-Al 900°C} was also studied. The residual fluoride concentration reduced from initial fluoride concentration 11.72 mg/L to {7.65 and 5.055 mg/L} after agitation for 2 hrs usingG-FeCl3.6H2O1000°C and G-Al900°C) respectively. Moreover, an alternative modification was done on the graphite sample (G-Al900°C) to enhance its property by coating it with Aluminum Hydroxide and its fluoride removal efficiency enhanced (fluoride removal 95.63% after agitation for 2 hrs). The equilibrium data obtained in this study were closely fitted with the Langmuir isotherm for graphite (G-Al900°C). The Freundlich isotherm model was the best description of fluoride adsorption by a modified graphite sample (mG Al900°C). Adsorption kinetics was also determined and the kinetic results obtained from those studies fitted well with the pseudo-second-order kinetic model.