Method for making and using a dye sorbent

A method of making and using a dye sorbent comprising:

• mixing a sawdust with sulfuric acid to form a sulfonating mixture,
• heating the sulfonating mixture at 100 to 200° C. at a reduced pressure of 0.01 to 0.25 atm 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 hydrogen peroxide solution 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 dye sorbent, wherein the dye sorbent is in the form of particles that pass through a sieve with 400 to 800 μm openings,
• wherein the dye sorbent has a moisture content of 0.1 to 10 wt % based on a total weight of sulfonated and oxidized sawdust, a pH of 2 to 7, a density of 0.35 to 0.65 g/cm3, a surface area of 1.75 to 2.85 m2/g, a sulfur content of 0.01 to 25 wt % and an oxygen content of 45 to 61 wt % each based on a total weight of the dye sorbent;
• then
• contacting the dye sorbent with an organic dye-contaminated aqueous solution comprising an organic dye in an amount of 150-200 mg of the dye sorbent per liter of the organic dye-contaminated aqueous solution to adsorb the organic dye onto the dye sorbent, wherein the dye sorbent removes 97.50 to 99.99% of the organic dye from the organic dye-contaminted aqueous solution based on an initial amount of organic dye present in the organic dye-containing aqueous solution.