Adsorption of pb(ii) from aqueous solution solution onto microwave and conventional method prepared activated carbon from teff husk using zncl2 as an activated agent

Abstract

Various agricultural wastes can be used as an adsorbent for heavy metal removal after chemical modification by heating into activated carbon due to increasing it efficiency. Teff husk wastes were considered as low cost, environmentally friendly and easily available materials. Until now, the removal efficiency of Pb(II) ions on activated carbon prepared from teff husk was not reported. Therefore, this work was done in order to evaluated the removal efficiency of Pb(II) ions on activated carbon prepared from teff husk using ZnCl 2 as an activating agent. The activation process was done in order to increase the adsorption capacities for removal of Pb(II) from aqueous solutions. The proximate analysis of adsorbent on microwave were I2 (805 mg/g), moisture contents (7.83%), ash contents (2.96%), volatile matter (12.4%), fixed carbon (76.81%) and on conventional were I 2 (576 mg/g), moisture contents (9.29%), ash contents (12.56%), volatile matter (20.98%), fixed carbon (57.17%). Activated carbon was characterized by FTIR and XRD, it was determined used UV/visible spectrophotometer. The effect of parameter onto teff husk activated carbon was conducted by range as adsorbent dosage (0.25 g to 3.5 g) initial concentration (0.25 ppm to 5.5 ppm), contact time (5 minute to 30 minute), pH (2 to 14) and temperature (318 K to 358 K). As a result, adsorption equilibrium was adsorbent dosage (2 g), initial concentration (0.25 ppm), contact time (20 minute), pH (6) and temperature (348 K). The best fitted of adsorption isotherms and kinetic model for the adsorption of Pb(II) were selected based on R 2 . Finally , Langmuir isotherms (0.993), pseudo second order (0.993), intraparticle diffusion (0.983), Elovich model (0.909), Liquid film diffusion (0.984) were the best fitted. The thermodynamic parameters on microwave activated carbon were ∆G o (-0.3939 KJ/mol to -16.72 KJ/mol), ∆H o (256.611 KJ/mol), ∆S o (0.858 KJ/K*mol) and on conventional activated carbon were ∆G o (-5.5002 KJ/mol to 9.8179 KJ/mol), ∆H o (81.751 KJ/mol), ∆S o (0.28808 KJ/K*mol). The adsorption capacity of teff husk activated carbon for removal of Pb(II) from aqueous solution is 10.31(mg/g) and it desorption is 85%. The adsorption is chemisorption, particle diffusions, endothermic in nature, randomly motion to the adsorbent and spontaneous in nature. In conclusion, teff husk activated carbon was efficient for removal of Pb(II) ions from aqueous solution and it is recycling process.