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METAL-PHOSPHONATE CHEMISTRY: SYNTHESIS, CRYSTAL STRUCTURE OF CALCIUM-AMINO TRIS -(METHYLENE PHOSPHONATE) AND INHIBITION OF CACO 3 CRYSTAL GROWTH

2004; Taylor & Francis; Volume: 179; Issue: 3 Linguagem: Inglês

10.1080/10426500490441514

1563-5325

Konstantinos D. Demadis, S.D. Katarachia,

Mine drainage and remediation techniques

Abstract Organic (poly)phosphonates are additives in water treatment that find broad use as mineral scale and corrosion inhibitors for a plethora of industrial applications. The phenomenon of precipitation of scale inhibitors has been studied intensively. This study reports the synthesis, characterization, and crystal structure of a Ca salt of AMP (AMP = Amino-tris-Methylene Phosphonate). Ca-AMP crystals are monoclinic, space group P 2 1 n with unit cell dimensions, a = 11.3382(5) Å, b = 8.4555(4) Å, c = 15.5254(7) Å, β = 90.6551 o , V = 1488.33(12) Å 3 and Z = 4. The structure is polymeric due to chelation of multiple Ca ions by AMP. The Ca 2 + center is slightly distorted octahedral and is surrounded by five phosphonate oxygens and a water molecule. CaO(P) bond lengths range from 2.2924(14) to 2.3356(14) Å. The CaO(H 2 O) bond distance is 2.3693(17). Each phosphonate group is monodeprotonated, and the nitrogen atom is protonated. CaCO 3 inhibition and crystal modification by AMP are also reported, together with synergistic effects with polyacrylate-based terpolymers. Keywords: AMPcalcium carbonatedispersant polymersphosphonatescale formationscale inhibition The authors wish to acknowledge Dr. Peter White for collecting the X-ray data and Nalco Chemical Company for supplying samples of polymers A and B. Notes a R = Σ Fo-FcΣ Fo. b Rw = [Σ (w Fo-Fc)2/Σw(Fo)2]1/2. c GoF = [Σw(Fo-Fc)2/(no. of reflections—no. of parameters)].1/2 a s, strong; m, medium; w, weak; sh, shoulder.