Tetrabasic lead sulfate

The carbonates, sulfates, nitrates, and haUdes of lead (except the yeUow iodide) are colodess. Bivalent lead forms a soluble nitrate, chlorate, and acetate a slightly soluble chloride and an insoluble sulfate, carbonate, chromate, phosphate, molybdate, and sulfide. Highly crystalline basic lead salts of both anhydrous and hydrated types are readily formed. Tetrabasic lead sulfate [52732-72-6] 4PbO PbSO, and the hydrated tribasic salt [12397-06-7] ... 

Tetrabasic Lead Sulfate. Tetrabasic lead sulfate [12065-90-6] 4PbO PbSO, mol wt 1196.12, sp gr 8.15, is made by fusion of stoichiometric quantities of Htharge (PbO) and lead sulfate (PbSO heat of formation, Ai/ = — 1814 kJ/mol (—434.1 kcal/mol). Alternatively, tetrabasic lead sulfate may be prepared by boiling the components in aqueous suspensions. At about 70°C, tribasic hydrate reacts with lead oxide to form tetrabasic sulfate. At 80°C, this transformation is complete in - 20 hours. Tetrabasic lead sulfate is used in limited quantities in Europe as a PVC stabilizer. However, in the United States, lead-acid batteries have been developed by BeU Telephone Laboratories, which contain tetrabasic lead sulfate. Such batteries are used for emergency power at telephone switchboard stations and have an anticipated service life of over 50 years. 

PbO TbSO H20. If the temperature is elevated to >57° C, the result is coarse tetrabasic lead sulfate, 4PbO TbSO, crystals. This is especially critical for the positive electrode where tribasic sulfate converts readily to Pb02 during battery formation but tetrabasic sulfate does not (93). 

Although several hypotheses have been proposed, the mechanisms of electrode degradation involved in shedding and inactivation processes are still not clear. The method of material preparation plays a substantial role here. For example, positive material prepared by oxidation of needle like crystals of tetrabasic lead sulfate HPbO PbS04) maintains the latter s morphology and the electrode s superior performance during cycling of stationary cells." ... 

Sulfate salts have been introduced into the positive paste of VRLA cells during the paste-mixing process. In a recent study [65], sodium sulfate was added to positive pastes at 0, 0.01, 0.05, 1, and 2M levels (note, the authors did not explain how the molarity levels were calculated). The plates were cured at 85°C to form tetrabasic lead sulfate and a-PbO. The tetrabasic lead sulfate crystals had sizes of... 

Tetrabasic Lead Sulfate Pastes, 4Pb0 PbS04 (4BS)... 

A sample scheme of the successive technological procedures involved in the process of 3BS paste preparation is presented in Fig. 6.32. An example of a formulation for 3BS paste preparation could be LO (78% PbO) — 500 kg, H2O — 65 L, H2SO4 (1.4 g cm ) — 39 L, fibres — 0.35 kg. For the conversion of the 3BS paste into 4BS during the plate curing procedure, some 6—7 kg of tetrabasic lead sulfate nucleants should also be added to the initial paste mix. 

Preparation of tetrabasic lead sulfate (4BS) pastes for positive plates. 

Tribasic and tetrabasic lead sulfate crystals (3Pb0PbS04-H20 and 4Pb0PbS04-xH20) contain water and are partly hydrated (x in the 4BS formula is a variable with a value between 0.18 and 0.16, i.e. 4BS crystals are superficially hydrated) [17]. PbO in the CL2 layer is hydrated, too. It can be expected that bonding between 3BS or 4BS particles of the paste and of the corrosion layer will occur by an interaction between their hydrated layers. 

Tetrabasic lead sulfate crystals are big in size (10—100 pm in length and 1—10 pm in diameter). The processes of sulfation of 4BS crystals have been studied by many scientists and the obtained results are summarised in [9,14—17]. Conjectures about the processes that occur on soaking 4BS pastes are made on grounds of the obtained phases across the 4BS crystal cross-section as a result of soaking (see Fig. 9.25). 

Curing the paste at higher temperature for extended hours will produce a high percentage of tetrabasic lead sulfate and result in a plate with lower energy density. At the end of curing, the free lead content of the paste should be lower than 2%. Table 7.2 lists the typical curing profiles. 

The use of pre-sulfated paste materials containing basic lead sulfate, e.g., tribasic and tetrabasic lead sulfates (3PbO x PbS04 x H2O and 4PbO x PbS04) made in dry form prior to forming the paste has also been proposed to improve the efficiency of the paste (13). 

G.N. Reich, Forming of tetrabasic lead sulfate battery electrodes, US Patent 4 415 410, assigned to Allied Corporation (Morristown, NJ),... 

If the tmns isomer of maleic acid, fumaric acid, is used instead, the resultant product has been characterized most often as tetrabasic, but sometimes as polybasic, lead fumarate. It is probably a mixture of C2H2[C(0H)(0—Pb—OH)2]2 and C2H2[C(0—Pb—0H)2]4, although intermediate products are possible. As with tetrabasic lead sulfate, this stabilizer is off-white or cream-colored and is UV light-sensitive, again yielding black colloidal PbO. Its major use is in low-smoke flame-retardant PVC compounds, where the long failure time provided helps to compensate for instability caused by other additives, particularly zinc compounds and brominated... 

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