The aluminum Keggin polycation (Al13) has been identified as an effective specie for neutralization and coagulation of anionic contaminants in water. In this study, we compare efficacy of the aluminum Keggin-ion to the analogues containing a single Ga-atom or single Ge-atom (GaAl12 and GeAl12, respectively) substituted into the center of the polycation in water-treatment studies. We investigated removal of bacteriophage (model viruses), Cryptosporidium, dissolved organic carbon (DOC), and turbidity. In every study, the order of contaminant removal efficacy trends GaAl12 > Al13 > GeAl12. By ESI MS (electrospray ionization mass spectrometry), we noted the GaAl12 deprotonates least of the three aluminum polycations, and thus probably carries the highest charge, and also optimal contaminant-neutralization ability. The ESI MS studies of the aluminum polycation solutions, as well as solid-state characterization of their resulting precipitates both reveal some conversion of Al13 to larger polycations, Al30 for instance. The GaAl12 does not show any evidence for this alteration that is responsible for poor shelf life of commercial prehydrolyzed aluminum coagulants such as polyaluminum chloride. Based on these studies, we conclude that substitution of a single Ga-atom in the center of the aluminum Keggin polycation produces an optimal water-treatment product due to enhanced shelf life and efficacy in neutralization of anionic contaminants.

Purpose Executive coaching has become increasingly important for enhancing organizational leaders’ professional effectiveness. The purpose of this paper is to contribute to a growing body of research literature that examines how coaching techniques help school principals improve their instructional leadership. Design/methodology/approach Using a protocol based on a theories of practice framework (Argyris and Schön, 1974) to support principals in deepening their self-reflection, this study added the element of a guided peer-coaching component in a group setting. Findings Results confirmed the effectiveness of the coaching protocol for assisting principals in deepening their self-awareness and critical reflection regarding their leadership, including the way principals’ core assumptions about teaching and leadership shaped the outcomes of their problem-solving strategies. Perceptions of the peer-coaching element were mixed, however. While principals reported feeling affirmed by sharing their leadership challenges with others, and indicated that the group coaching experience contributed to their sense of professional community, there were limitations to principals’ willingness to challenge one another’s core assumptions. Originality/value This study builds on literature that cites theories of practice as a mechanism for enhancing professional effectiveness and represents a further iteration of recent research studies applying the concept to the work of school principals. Findings affirm that a coaching protocol based on theories of practice is well received by principals, serves to deepen self-reflection, and can, in limited cases, contribute to sweeping changes of thinking and practice congruent with the concept of double-loop learning.