Method of producing modified sawdust sorbent from sulfonated and oxidized sawdust and a method of water purification

2:

• The method of claim 1, wherein the sawdust is yellow pine sawdust.

3:

• The method of claim 1, wherein the sawdust is present in the sulfonating mixture in an amount of 45 to 65 wt % and the sulfuric acid is present in the sulfonating mixture in an amount of 35 to 55 wt %, each based on a total weight of the sulfonating mixture.

4:

• The method of claim 1, wherein the sulfuric acid is dilute sulfuric acid having a concentration of 0.1 to 4.2 mol/L.

5:

• The method of claim 1, wherein hydrogen peroxide is present in the hydrogen peroxide solution in an amount of 1 to 10 vol %, based on a total volume of the hydrogen peroxide solution.

6:

• The method of claim 1, wherein the treating is performed at ambient temperature for 1 to 3 hours.

7:

• The method of claim 1, wherein the sieving is performed with a sieve with 400 to 800 μm openings.

8:

• The method of claim 1, wherein the washing of the sulfonated sawdust and the washing of the peroxide-treated sawdust are performed with water.

9:

• The method of claim 1, wherein the heating of the sulfonating mixture is performed in a vacuum oven at a pressure of 0.01 to 0.25 atm.

10:

• The method of claim 1, where the drying of the sulfonated sawdust and the drying of the peroxide-treated sawdust are performed in a vacuum oven at a pressure of 0.01 to 0.25 atm.

11:

• The method of claim 1, wherein the modified sawdust sorbent has a moisture content of 0.1 to 10 wt % based on a total weight of modified sawdust sorbent, a pH of 2 to 7, a density of 0.35 to 0.65 g/cm3, and a surface area of 1.75 to 2.85 m2/g.

12:

• A modified sawdust sorbent comprising a sulfonated and oxidized sawdust having 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, and a dye adsorption capacity of 20 to 50 mg of dye per g of sorbent at 25 to 45° C.

13:

• The modified sawdust sorbent of claim 12, which is in the form of particles that pass through a sieve with 400 to 800 μm openings.

14:

• The modified sawdust sorbent of claim 12, which has 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 modified sawdust sorbent.

15:

• A method for removing a dye from a contaminated water comprising:
• contacting the contaminated water with the modified sawdust sorbent of claim 12, and
• isolating the modified sawdust sorbent to produce a dye-impregnated sorbent and decontaminated water.

16:

• The method of claim 15, wherein a weight ratio of the modified sawdust sorbent to the dye at a beginning of the contacting is 250:1 to 50:1.

17:

• The method of claim 15, wherein the modified sawdust sorbent removes 97.50 to 99.99% of the dye from the contaminated water based on an initial amount of dye present in the contaminated water.

18:

• The method of claim 15, wherein the contacting comprises an adsorption having a free energy change of −6.5 to −2.75 kJ/mol of dye adsorbed.