High concentration of fluoride in wastewater discharge from various industries is threatening the environment due to its hazardous effects and properties. This research work aims to develop an efficient adsorbent for fluoride removal in wastewater. Graphite oxide (GO) was impregnated
with ZnO nanoparticles as an adsorbent, and the effect of synthesis parameters of GO-ZnO adsorbent for fluoride removal were studied (sonication temperature, synthesis time, and ratio of GO to ZnO). The surface functional groups of these synthesized adsorbents were analyzed by
using FTIR. The synthesis parameters that contribute to the highest adsorption capacity and percentage removal are 5:1 ratio of GO-ZnO, 45 ºC of sonication temperature and 60 minutes of synthesis time, respectively. The highest value of adsorption capacity obtained from the fluoride
removal is 55.5 mg/g. The functional groups contained in the GO-ZnO adsorbent are hydroxyl group (O-H), C=O group, aromatics group, carboxyl group (C-O), epoxy group and alkoxy group. These functional groups showed significant impact towards fluoride adsorption due to the bonding of fluoride ion to the functional groups.
The adsorption of phenol, from aqueous solutions on activated carbon from waste tyres, was studied in a batch system at different initial concentrations (100-500mg/L) at 30°C for 48 hours. The activated carbon was prepared using the two-step physiochemical activation, with potassium hydroxide (KOH) at ratio KOH/char = 5. The carbonization process was done at 800°C for 1 hour with nitrogen flow rate 150ml/min, followed by the activation with the carbon dioxide flow rate 150ml/min at 800°C for 2 hours. The adsorption isotherms were determined by shaking 0.1g of activated carbon with 100ml phenol solutions. The initial and final concentrations of phenol in aqueous solution were analyzed using the UV-Visible Spectrophotometer (Shimadzu, UV-1601) at a wavelength of 270nm. Experimental isotherm data were analyzed using the Langmuir and Freundlich isotherm models.The equilibrium data for phenol adsorption could fit both isotherm models well with the R2 value of 0.9774 and 0.9895, respectively. The maximum adsorption capacity of the adsorbent obtained from the Langmuir model was up to 156.25 mg/g