Effects of pretreatment on the surface chemistry and pore size properties of nitrogen functionalized and alkylated granular activated carbon

► The effects of pretreatment on the surface chemistry and pore sizes were studied. ► Treated GAC was nitrogen functionalized and alkylated GAC also called modified GAC. ► HNO3 pretreatment caused a slight decrease in surface area and microporosity. ► The nitrogen percentage of modified GAC which pretreated by H2O2 was 4.07%. ► The pyridine of modified GAC which pretreated by urea-formaldehyde resin was 45.88%.