Method for sulfonating and oxidizing sawdust to form a sorbent

Method for sulfonating and oxidizing sawdust to form a modified sawdust sorbent comprising:

• mixing the sawdust with sulfuric acid to form a sulfonating mixture,
• heating the sulfonating mixture at 100 to 200° C. to form a sulfonated sawdust,
• washing and drying the sulfonated sawdust at 50 to 150° C. to form a dried sawdust,
• treating the dried sawdust with a 3-5 vol % hydrogen peroxide solution in an amount of 350 to 650 mL of hydrogen peroxide solution per 100 g of dried sawdust to form a peroxide-treated sawdust,
• washing and drying the peroxide-treated sawdust at 50 to 150° C. to form a sulfonated and oxidized sawdust, and
• milling and sieving the sulfonated and oxidized sawdust to form the modified sawdust sorbent,
• wherein the modified sawdust sorbent has a dye adsorption capacity of 20 to 25 mg of dye per g of sorbent at 25 to 45° C.