Exploring the Potential of Biochar Activated with Phosphoric Acid towards Hexavalent Chromium Removal

The biochar derived from the dreadful weed water hyacinth (Eichhornia crassipes) was activated with phosphoric acid was utilized for adsorption of hexavalent chromium (Cr (VI)) from the simulated solution. The characterization (Zeta potential, specific surface area, Scanning Electron Microscope analysis) of biochar was done to study the surface properties of the biochar. The modified biochar (379 m2g-1) recorded 49.80% greater surface area in comparison to the pristine biochar (253 m2g-1). Zeta potential of modified biochar is 4.2 mV and pristine biochar is -13.9 mV. Positively charged modified surface enhance the sorption of negatively charged Cr (VI) ions. Study on effect of pH and concentration revealed that maximum sorption occurred at pH 2 and the increasing trend of concentration resulted in the decreased sorption respectively. The isotherm study was well supported by Langmuir isotherm (R2 value=0.976) defining the monolayer adsorption. Maximum adsorption capacity was recorded for phosphoric acid modified biochar (50.0 mg g-1) than the pristine biochar (35.7 mg g-1). Pseudo second order kinetics (R2 value=0.998) sounds good in explaining the rate of reaction. The findings reflect the utility of acid modified Eichhornia crassipes for heavy metal removal from aqueous medium.