mixing {HEAD ~ the ammonia containing solution} with {TAIL ~ the recovered solid phase} to neutralize the solid phase and to enrich it in nitrogen 
with
mixing { HEAD ~ the ammonia containing solution } with { TAIL ~ the recovered solid phase } to neutralize the solid phase and to enrich it in nitrogen
OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH