China
Africa
Explore chapters and articles related to this topic
Water quality and treatment
Published in Bogumil Ulanicki, Kalanithy Vairavamoorthy, David Butler, Peter L.M. Bounds, Fayyaz Ali Memon, Water Management Challenges in Global Change, 2020
Bogumil Ulanicki, Kalanithy Vairavamoorthy, David Butler, Peter L.M. Bounds, Fayyaz Ali Memon
Raymond, 1974, and Raymond et al., 1986 patented the ISB technology for the use of hydrogen peroxide as a source pf oxygen for bioremediation processes in places with contaminated ground. The ISB technology is the most effective for biodegradation of dissolved contamination. Chiang et al., 1989 noted that increasing the efficiency of destruction of organic compounds is often achieved by adding various mass ratios of oxygen as an electron acceptor to the organic pollution that goes through oxidation. In ground waters, when, anaerobic remediation processes take place, such methods as aeration by air, injection of pure oxygen, addition of hydrogen peroxide and solid metal peroxides are used for increasing of oxygen concentrations. However, Raymond, 1974; and Raymond et al., 1986 consider that the addition of hydrogen peroxide is the most promising techniques to increase the oxygen content in a bioremediation medium.
Theory of chemical bonds in metalloenzymes XXIII fundamental principles for the photo-induced water oxidation in oxygen evolving complex of photosystem II
Published in Molecular Physics, 2020
K. Yamaguchi, S. Yamanaka, H. Isobe, M. Shoji, K. Miyagawa, T. Kawakami
Therefore, the sign of Jab determines the selection rules for OEST between Mna and Mnb ions in OEC of PSII; namely exchange-allowed for parallel spins () (Jab > 0) in Figure 3(C) and exchange-forbidden for antiparallel spins () (Jab < 0) as shown in Figure 3(D) [36,62]. Thus, we have the next fundamental principle (FP2) as follows:FP2: The Mn (III) and Mn(IV) ions in OEC of PSII are local high spins which are the origin of one-electron transfer (OEST) processes controlled by spin degree of freedom.FP2 is very important for understanding other OEST processes for native water oxidation. For example, the principle of FP2 for OEST is applicable for evolution of triplet molecular oxygen (3O2) from the transition metal peroxide M-M bond of the M-oxide clusters such as CaMn4O6 as shown in Equation (3a). The ferromagnetic exchange coupling between the metal ions plays an important role of generation of triplet spin coupling state for molecular oxygen [57,62]. The OEST is also applicable to the one electron oxidation of CaMn4O5 cluster with tyrosine (Tyr) 161-radical in Equation (3b) where the back-electron transfer from the oxygen anion site Tyr-O− to the generated hole of the CaMn4O5 cluster is suppressed with its rapid protonation by trapped proton with His190. where Tyr-O•↓ is formed with the OEST (electron with •↑) from Tyr-OH to chlorophyll cation radical (•↓) generated by the photo-excitation in P680, sensitiser consisted of chlorophyll pigments.