Separation And Recovery Of Valuable Phosphorus Compounds From Glyphosate Mother Liquid

Glyphosate is the most widely used herbicide at present.However,a large amount of glyphosate mother liquid rich in valuable phosphorus compounds such as glyphosine,glyphosate and phosphorous acid is produced in its production process.The glyphosate mother liquid is usually treated by incineration,which not only results in enormous resources waste but also causes serious environmental pollution.Therefore,it is urgent to carry out research on the separation and recovery of valuable phosphorus compounds,in order to realize the harmless disposal and resourceful utilization of glyphosate mother liquor.In this paper,the high value phosphorus compounds in glyphosate mother liquor were separated and recovered by a combined chemical precipitation and adsorption method.The effects of different metal ion precipitants on the precipitation efficiency of glyphosine,glyphosate and phosphorous acid from glyphosate mother liquor were investigated.The adsorption behavior and mechanism of 001*7 resin and D301 resin for excess Ca²⁺and three kinds of valuable phosphorus compounds in glyphosate mother liquor were studied.The main contents are as follows:（1）Three kinds of metal ion precipitants,Al³⁺,Mg²⁺and Ca²⁺,were studied in this paper,and Ca²⁺was selected as the best precipitant from the point of precipitation effect and environmental protection.The effects of precipitant dosage,time,temperature and acidity on the precipitation effect of total phosphorus in glyphosate mother liquor were discussed.The results showed that the optimal dosage of Ca²⁺in 100.00 m L glyphosate mother liquor was 0.1mol,and the mole ratio of calcium to phosphorus was 1:1.The precipitation kinetics experiment showed that the precipitation reaction reached equilibrium within 30 min.The precipitation reaction is a exothermic process,which can be carried out at room temperature.The precipitation effect at p H above 9.00 is best.Under the optimum conditions,the precipitation rate of total phosphorus in glyphosate mother liquor can reach 98.90%,and the residual concentration of total phosphorus in mother liquor is 374.00 mg/L.（2）The stepwise recovery of three kinds of valuable phosphorus compounds（glyphosine,glyphosate and phosphorous acid）in glyphosate mother liquor with low concentration by D301 resin was studied.The effects of initial concentration,time and acidity on the adsorption of three valuable phosphorus compounds were investigated.The results showed that D301 resin has a wide range of adsorption p H,fast adsorption rate and good reusability.The maximum theoretical adsorption capacity of glyphosine,phosphorous acid and glyphosate are 781.40 mg/g,603.50 mg/g and 392.20 mg/g,respectively.The adsorption equilibrium can be reached in 200 min,and the optimal adsorption p H is3.00.The affinity and selectivity of D301 resin for glyphosine were much higher than glyphosate and phosphorous acid.The results showed that D301 resin could selectively recover glyphosine from glyphosate mother liquid at the dosage of 3.00 g.When the amount of adsorbent increased to 6.00 g,glyphosate and phosphorous acid can be effectively recovered,indicating that the recycling of valuable phosphorus compounds could be achieved by controlling the dosage of D301 resin.XPS,FTIR and characterization analysis showed that the adsorption mechanism of D301 resin toward the three phosphorus compounds included ion exchange,electrostatic attraction and hydrogen bond.To be specific,Cl^-on the resin exchanged with anions of the three phosphorus compounds in aqueous solution,which were then electrostatically adsorbed with the positively charged tertiary amine group on the resin.（3）The adsorption behavior of Ca²⁺on 001*7 resin was studied.The results showed that the adsorption isotherms and kinetic curves of Ca²⁺on 001*7 resin were in line with Langmuir model and pseudo-second-order model,respectively,and the theoretical maximum adsorption capacity could reach 52.87 mg/g.The adsorption equilibrium could be reached in 20 min,and the adsorption amount was not affected by the initial p H of solution.The adsorption mechanism was the ion exchange between the H+of sulfonic acid group on 001*7 resin and Ca²⁺in the solution.The regeneration experiment showed that the 001*7 resin had good reusability.After five consecutive adsorption-desorption cycles with 3.00%HCl solution as the eluent,the adsorption amount of Ca²⁺on the resin did not change obviously,and the Ca²⁺desorption rate was above 98.90%.Moreover,the resin did not adsorb the three phosphorus compounds,and release any new organic impurities during the adsorption process,indicating that it is a good decalcification material.（4）The adsorption behavior of 001*7 resin for Ca²⁺and D301 resin for the three phosphorus compounds was investigated under dynamic conditions.The optimal flow rate was 7.21 m L/min,and the adsorption capacity of 001*7 resin for Ca²⁺was 21.90mg/g.The adsorption capacities of D301 for glyphosine,glyphosate and phosphorous acid were 455.80,183.00 and 241.40 mg/g,respectively.In two-component and three-component systems,the adsorption affinity and selectivity of D301 resin for glyphosine were significantly higher than that of phosphorous acid and glyphosate,showing obvious competitive substitution phenomenon.The results showed that 001*7resin and D301 resin could be used for the harmless treatment of glyphosate mother liquor.The Ca²⁺in the solution could be completely removed,and the residual concentration of total phosphorus was 1.2 mg/L,indicated that the combined application of 001*7 resin and D301 resin could achieve the efficient treatment of glyphosate mother liquor.