Treatment of Effluent from Manufacture of Chlorinated Pesticides with a Synthetic, Polymeric Adsorbent, Amberlite XAD-4 David C. Kennedy Research Division, Rohm a n d Haas Co , Philadelphia, Pa 19137
w A new process is described for treating chlorinated pesticide waste effluents. Pesticides are adsorbed on Amberlite XAD-4, a newly developed synthetic, polymeric adsorbent possessing high porosity (50 vol YO),high surface area (850 m2/g) and a n inert, hydrophobic surface. The adsorbent is regenerated with an organic solvent, and the adsorbed pesticides are recovered in a concentrated form. Laboratory studies are reported in which XAD-4 and a commercial, granular activated carbon were compared for treating the effluent from a pesticide manufacturing operation. The leakage of unadsorbed pesticides from the XAD-4 column was significantly lower than t h a t from the activated carbon column. The adsorbed pesticides were efficiently desorbed from XAD-4 by eluting with isopropanol. The activated carbon could not be regenerated effectively with isopropanol. An estimate of capital and operating expenses for a full-scale facility is presented. This projection indicates that pesticides waste treatment via XAD-4 and chemical regeneration will be more economical than granular activated carbon employing external thermal regeneration.
Amberlite (trademark of Rohm and Haas Co.) XAD-4 is a synthetic, polymeric adsorbent. It is characterized by an inert-Le., not activated-hydrophobic surface and by high porosity and surface area. As a consequence, XAD-4 is capable of efficiently adsorbing large quantities of hydrophobic, organic species from water. Furthermore, the adsorption process is reversible so that XAD-4, unlike most other adsorbents, can be easily regenerated chemically. This report considers the specific application of the treatment of industrial waste streams which contain chlorinated pesticides. Presented are the results of laboratory experiments which were performed with pesticides waste effluents from a pesticide manufacturing facility. Based on these studies a waste treatment process utilizing XAD-4 adsorbent has been developed and is now being used to treat the effluent a t this pesticide manufacturer’s facility.
as activated carbon. In the form of hard, resilient, polymeric beads, XAD-4 is highly attrition resistant. The chemically inert surface permits a reversible adsorption mechanism which allows efficient chemical regeneration. The high porosity, high surface area, and uniform pore distribution favor rapid adsorption kinetics and hence high operating capacity and low leakage. A large amount of laboratory data has been generated using model compounds of the type often encountered in industrial waste treatment problems. Typical is the work performed with phenol and chlorophenols (Paleos, 1969). As seen in Table I, under practical operating conditions, large quantities of these materials can be adsorbed on a column of XAD-4 adsorbent with no detectable leakage. Note that the capacity of Amberlite XAD-4 is greatest for the most hydrophobic species as indicated by decreasing solute solubility in water. Pesticides, in general, are extremely hydrophobic. This suggests t h a t XAD-4 should be effective for removing these materials from aqueous systems. The data available in the literature support this hypothesis. The adsorption of two pesticides-Parathion and Sevin-on Amberlite XAD-2 adsorbent has been reported
-
120
5
0
I00
-
u I-
W v)
a
80
W
I-
f
5
60
0 I LL
0 W
40 Y
4: W
20
Background Some pertinent physical properties of Amberlite XAD-4 are: composition, crosslinked polystyrene copolymer; form, 20-50 mesh beads; bead porosity, 51 vol 70;surface area, 750 m2/g; average pore diam, 50 A. These characteristics provide XAD-4 with adsorption properties which offer certain advantages over conventional adsorbent such
IO
20
30
BED VOLUMES
40
Figure 1. Treatment of a waste effluent from the manufacture of chlorinated pesticides with Amberlite XAD-4
Table I. Column Operating Capacity of Amberlite XAD-4 for Some Model Compounds
Flow rate:
Leakage level: Temp:
0.5 gpm/ft3
