Persulfate Activation

Persulfate activation is the requirement, central to Marvin Antelman's claims about Tetrasilver Tetroxide (Ag₄O₄), that the Ag₄O₄ crystals are inert against pathogens unless activated by an oxidizing agent. The activators named in the dossier are persulfates — from DuPont's Oxone (potassium monopersulfate) to alkali peroxydisulfates — or hydrogen peroxide.

The claim

The dossier states: "When the tetroxide crystals are utilized to destroy pathogens, they will not do so unless activated by an oxidizing agent." Antelman compares this to the behavior of single semiconducting photovoltaic molecular devices such as copper indium selenide, whose surfaces must be "etched" to activate photovoltaic activity.

The dossier reports that persulfates tested alone as a control "failed to exhibit any unilateral antipathogenic activity at the optimum level selected of 10 PPM." Technical-grade TSTO is said to contain trace Oxone as activator and potassium/sodium sulfate as stabilizer.

Oxone and potassium peroxymonosulfate

Oxone (DuPont) and Caroat (Evonik, formerly Degussa) are trade names for potassium peroxymonosulfate, the potassium salt of peroxymonosulfuric acid. It is supplied as a triple salt with the formula 2KHSO₅·KHSO₄·K₂SO₄ (CAS 37222-66-5, molecular weight 614.76, water solubility 250 g/L at 20 °C). The standard electrode potential is +1.44 V:

HSO5- + 2 H+ + 2 e-  →  HSO4- + H2O

Oxone is a versatile oxidant: it oxidizes aldehydes to carboxylic acids (and to esters in alcoholic solvents), cleaves internal alkenes to two carboxylic acids, epoxidizes terminal alkenes, converts thioethers to sulfones, tertiary amines to amine oxides, and phosphines to phosphine oxides. It is used in swimming pools to keep water clear so that chlorine can sanitize rather than clarify.

Persulfate in the preparation chemistry

Persulfate is also the oxidant in the preparation of Ag₄O₄ itself. In acidic media, persulfate oxidizes Ag(I) to the brown Ag(III) ion:

Ag+ + S2O8^2-  →  Ag3+ + 2 SO4^2-

The Ag(III) ion is unstable and slowly oxidizes water, precipitating the mixed-valence oxide:

4 Ag3+ + 6 H2O  →  2 Ag(I)Ag(III)O2 + 12 H+ + O2
4 Ag3+ + 12 OH-  →  2 Ag(I)Ag(III)O2 + 6 H2O + O2

Silver nitrate also acts as a catalyst for persulfate oxidations in acidic media, via an Ag³⁺ intermediate. See Silver(III) Chemistry.

Regulatory use

The EPA efficacy review for SILDATE (N. Jonas & Co., EPA Reg. No. 3432-AU) specifies an activator, "Energize" (potassium persulfate), at 1 pound per 10,000 gallons, with the product applied at 1 ppm. This is the one documented, regulator-reviewed use of the activation scheme.

Tensions

The activation requirement sits awkwardly beside other claims in the dossier. US5223149 claims trivalent silver complexes "were effective without persulfates as bactericides," and US2006105057 describes dermatological compositions "substantially free of added persulfates." The dossier does not reconcile these with the core activation claim.

Related pages

• Tetrasilver Tetroxide (Ag₄O₄)
• Molecular Crystal Device (Electron Jumping Compound)
• Silver(III) Chemistry
• Mixed-Valence Metal Oxides