Pii: S0043-1354(99)00052-4

ÐA ®xed bed reactor ®lled with calcite particles (mean strokes diameter, 0.20 mm) was constructed and the reactor was used to treat synthetic wastewater containing HF, NaF, NH4F or Na2SiF6 under various conditions. Calcium ions (Ca) were found to exist in the treated e‚uent and the molar Ca concentration ([Ca]) was related to the molar ratio of H to Fÿ ([H]0/[F ]0) in in ̄uent as log10[Ca ]=0.020[H]0/[F ]0ÿ4.24. The e‚uent Fÿ concentration was determined by the concentration of e‚uent Ca as [Fÿ]2[Ca2+]0.94=3.98 10ÿ10 under an SV of 1.0 to 5.0 hÿ1 and 258C. This equation was similar with that of the solubility product of CaF2 and could be applied to wastewaters containing HF, NaF, NH4F or Na2SiF6 under an in ̄uent F ÿ concentration ranging from 25 to 3000 mg lÿ1. The e‚uent Fÿ was also found to be related to e‚uent pH as log10[F ÿ]=0.51pHÿ2.91. The e‚uent Fÿ was about 6 mg lÿ1 at an e‚uent Ca of 80 mg lÿ1 or e‚uent pH of 6.8 under the above conditions. The e‚uent Fÿ increased from 6 to 12 mg lÿ1 and e€ective calcite conversion rate decreased from ca. 60 to 40% when SV was increased from 1.6 to 16.0 hÿ1 at a [H]0/[F ]0 of 0.75. Signi®cant increase of e‚uent Fÿ as well as decrease of e€ective calcite conversion rate was observed when reaction temperature was decreased to 8.58C at an SV of 7 hÿ1 and [H]0/[F ]0 of 0.75. The performance of the reactor was a€ected by the existence of SO4 2ÿ to some extent and signi®cantly inhibited by PO4 3ÿ. A molar ratio of PO4 3ÿ to Fÿ higher than 0.05 stopped Fÿ removal at a PO4 3ÿ of 15 mg lÿ1. # 1999 Elsevier Science Ltd. All rights reserved Key wordsÐ ̄uoride removal, calcite, replacement, wastewater treatment