Efficient treatment of glyphosate mother liquor by a coagulation and adsorption combined process

Glyphosate is an effective weedicide that is widely used. During glyphosate production, large quantities of mother liquor containing glyphosate, glyphosine, and phosphorous acid are produced, which can cause severe environmental damage. To efficiently deal with the glyphosate mother liquor, a combination of coagulation-adsorption techniques was developed. First, FeCl3, FeSO4, and polyferric sulfate (PFS) were selected as the coagulants for treating the glyphosate mother liquor, and the best conditions for total phosphorus removal were explored. Then, the excess phosphorus was removed from the supernatant of the treated mother liquor by using ferrihydrite/bagasse (FH/SCB) sorbent. The results showed that FeCl3 could remove 99.9% of the phosphorus compounds, and the total phosphorus concentration was reduced from 26.7 g/L to 0.015 g/L. FH/SCB exhibited a high adsorption capacity of 94.3, 89.1, and 84.7 mg/g for the typical compounds of glyphosate, glyphosine, and phosphorous acid. The adsorption process of phosphorus compounds by FH/SCB was completed in 120 min, and the anti-anion interference performance was excellent. Under dynamic conditions, the adsorption properties of FH/SCB remained unaffected. The total phosphorus in the glyphosate mother liquor can be reduced to less than 0.5 mg/L through the combination of coagulation-adsorption techniques, thereby meeting the discharge standard for industrial wastewater. In conclusion, the combination of coagulation-adsorption technology offers a promising method for treating high-concentration organophosphate wastewater.