Two new yet structurally similar scale inhibitors (PASP-AAB and PASP-AAA), have been successfully synthesized through ring-opening reaction of polysuccinimide (PSI) with inexpensive (4-[(2-aminoethyl) amino]-4-oxobutanoic acid or glycylglycine. Static antiscaling experiments imply they could dramatically improve the antiscaling efficiency of gypsum, better than that of PASP. Moreover, the slightly different nitrogen atom position on the side chain of PASP-AAB and PASP-AAA enables the former efficiently inhibit the gypsum scale at low concentration (2.0 mg/L). In addition, our results indicate the antiscaling performance of PASP-AAB (at 4.0 mg/L) could maintain the excellent efficiency (>99 %) against gypsum for at least 7 days, better than that of some reported polymer-, and phosphorus-based industrial antiscalants. The very efficient gypsum scale inhibition property of PASP-AAB makes it as one of the very effective green antiscalants reported in the literature by now. Detailed mechanism studies reveal that the better calcium scale inhibition performance of PASP-AAB should be attributed to the easier formation of seven-membered chelation ring of side chain with Ca 2+ . The unprecedented nitrogen substitution effect disclosed in this work provides a new perspective for understanding the structure-activity relationship of the grafting-modified polymeric inhibitor, meaningful for developing other novel green scale inhibitors.
Yi Wu,Anqi He,Da Li,Limin Yang,Yizhuang Xu,Yukihiro Ozaki,Isao Noda
This study investigates single-crystal structures of Lu3+/erythritol and nine rare earth–glycerol complexes, revealing deprotonation of normally inert OH groups via μ2-bridging (so-called DIOμ2 phenomenon). The pH drops upon alditol addition correlate with the deprotonation extent, showing increased deprotonation with decreasing lanthanide ionic radius (lanthanide contraction) and exceptionally high deprotonation for Sc3+. In all the rare earth/alditol complexes with the DIOμ2 phenomenon, two μ2-bridges merge into an M2O2 cluster (M is a rare earth ion) that is not very stable due to the Coulombic repulsion between two M3+ and between two O–. To stabilize the M2O2 cluster, the formation of more auxiliary five- and six-membered chelating rings between rare earth ions and alditol ligands is needed. Increment of the number of auxiliary five- and six-membered chelating rings favors the DIOμ2 reaction. This is the reason why the DIOμ2 reaction shows a progressively enhanced tendency when the alditol ligands change from myo-inositol to glycerol to erythritol and galactitol. The reaction is endothermic, as an increased temperature enhances deprotonation. The above results may be useful in the rational design of catalysts that efficiently activate inert OH bonds and facilitate related chemical processes.
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