Effect of biocides and anionic homopolymeric inhibitors on the precipitation behavior of calcium fluoride

Abstract

This paper describes the effect of biocides and of the anionic homopolymeric inhibitors on the precipitation behavior of calcium fluoride (CaF₂).The efficiency of inhibitors in the presence and absence of biocides was calculated using the half-life (t_1/2) approach, where 50% of the concentration has been precipitated. Conductometric and X-ray diffraction (XRD) analysis have been performed for the calcium fluoride scale minerals using three polymeric inhibitors and three biocides, which are commonly used in industrial processes. The main aim of the study was to investigate the role of anionic homopolymerspoly(acrylic acid) PAA, and of the oxidizing and non-oxidizing biocides such as; sodium hypochlorite, gluteraldehyde, tris(hydroxymethyl) nitromethane). It was found that addition of low concentration (1-10 mg/L) of the polymers (K-752, K-732 and K-702) have great inhibitory effect on the precipitation of calcium fluoride (CaF₂). Their inhibition efficiency was in the order, K-752 > K-732 > K-702. The observed behaviour can be attributed to the effect of molecular weight of the polymer. The polymer having higher molecular weight shows weaker inhibiting ability. However, the oxidizing and non-oxidizing biocides have no appreciable effect on their performance and hence on the overall inhibition process.

KEY WORDS: Calcium fluoride, Precipitation, Inhibition, Homopolymeric inhibitors, Biocides

Bull. Chem. Soc. Ethiop. 2017, 31(1), 115-126.

DOI: http://dx.doi.org/10.4314/bcse.v31i1.10