Biochars produced by pyrolysis of corn cob(600℃) which is agricultural waste

and modified with hydrochloric acid

hydrogen peroxide and nitric acid separately. Elemental analysis

BET-N2 surface area (SA)

scanning electron microscopy

Boehm titration and FTIR spectra were used to characterized their physicochemical properties. Batch experiments were conducted to investigate ammonium adsorption process of corn cob biochars. The results revealed that acid modification can significantly improve biochars' specific surface area

which were 17.74

212.89

208.74 and 209.15 m2·g-1 for without modified and modified with HCl

HNO3 and H2O2 samples

respectively; while the amounts of acidic functional groups were 0.11

0.95

5.73 and 2.15 mmol·g-1

respectively. The results for fitting experimental data of adsorption process with isotherm models showed that it is better for Freundlich isotherm model than Langmuir isotherm model. Moreover

the adsorption process can be well described by pseudo-second-order kinetic model. The results obtained demonstrated that biochars modified with nitric acid have the highest adsorption capacity because of more acidic functional groups.