Phosphite radicals and their reactions. Examples of redox, substitution, and addition reactions

Advanced oxidation removal of hypophosphite by O3/H2O2 combined with sequential Fe(II) catalytic process

Elimination of hypophosphite (HP) was studied as an example of nickel plating effluents treatment by O₃/H₂O₂ and sequential Fe(II) catalytic oxidation process. Performance assessment performed with artificial HP solution by varying initial pH and employing various oxidation processes clearly showed that the O₃/H₂O₂─Fe(II) two-step oxidation process possessed the highest removal efficiency when operating under the same conditions. The effects of O₃ dosing, H₂O₂ concentration, Fe(II) addition and Fe(II) feeding time on the removal efficiency of HP were further evaluated in terms of apparent kinetic rate constant. Under improved conditions (initial HP concentration of 50 mg L^-1, 75 mg L^-1 O₃, 1 mL L^-1 H₂O₂, 150 mg L^-1 Fe(II) and pH 7.0), standard discharge (<0.5 mg L^-1 in China) could be achieved, and the Fe(II) feeding time was found to be the limiting factor for the evolution of apparent kinetic rate constant in the second stage. Characterization studies showed that neutralization process after oxidation treatment favored the improvement of phosphorus removal due to the formation of more metal hydroxides. Moreover, as a comparison with lab-scale Fenton approach, the O₃/H₂O₂─Fe(II) oxidation process had more competitive advantages with respect to applicable pH range, removal efficiency, sludge production as well as economic costs.

Phosphorus: a case for mineral-organic reactions in prebiotic chemistry

The ubiquity of phosphorus (P) in modern biochemistry suggests that P may have participated in prebiotic chemistry prior to the emergence of life. Of the major biogenic elements, phosphorus alone lacks a substantial volatile phase and its ultimate source therefore had to have been a mineral. However, as most native P minerals are chemically un-reactive within the temperature-pressure-pH regimes of contemporary life, it begs the question as to whether the most primitive early living systems on earth had access to a more chemically reactive P-mineral inventory. The meteoritic mineral schreibersite has been proposed as an important source of reactive P on the early earth. The chemistry of schreibersite as a P source is summarized and reviewed here. Recent work has also shown that reduced oxidation state P compounds were present on the early earth; these compounds lend credence to the relevance of schreibersite as a prebiotic mineral. Ultimately, schreibersite will oxidize to phosphate, but several high-energy P intermediates may have provided the reactive material necessary for incorporating P into prebiotic molecules.

Removal of citrate and hypophosphite binary components using Fenton, photo-Fenton and electro-Fenton processes

Both citrate and hypophosphite in aqueous solution were degraded by advanced oxidation processes (Fe2+/H2O2, UV/Fe2+/H2O2, and electrolysis/ Fe2+/H2O2) in this study. Comparison of these techniques in oxidation efficiency was undertaken. It was found that Fenton process could not completely degrade citrate in the presence of hypophosphite since it caused a series inhibition. Therefore, UV light (photo-Fenton) or electron current (electro-Fenton) was applied to improve the degradation efficiency of the Fenton process. Results showed that both photo-Fenton and electro-Fenton processes could overcome the inhibition of hypophosphite, especially the electro-Fenton.