BATTERY INDUSTRY WASTE-WATER - PB REMOVAL AND PRODUCED SLUDGE

The process of neutralization with NaOH, in the presence of Fe(III) sa lt, of sulphuric acid battery industry wastewater seems to be more sui table than any other process for Pb removal because at the same time, it allows the exploitation of the scavenger action of Fe(III), which i s often present in the same wastewater and precipitates as hydroxides. In order to optimize sludge production, a laboratory research study h as been carried out to minimize the quantity of Fe(III) to be added. A ll aspects concerning the chemistry of wastewater have been taken into consideration step by step and discussed. As a result, a process whic h requires the addition of Fe(III) so that an Fe/Pb ratio, both expres sed as ppm, of the order of 0.5 is achieved. The process has been appl ied to two artificial solutions, characterized by a content of H2SO4 o f 1000 and 5000 ppm, respectively, and by 10 ppm of Pb, as well as to five samples of wastewater. The proposed process takes about 1 h to pe rform: 30 min for neutralization up to pH 8.5-9.5 and Fe(III) addition and 30 min for correction in the 9-9.5 pH range and for flocculation with the help of a polyelectrolyte. The Pb concentration of the treate d effluent is below 0.2 ppm. Conditions for Pb removal using only NaOH or Na2CO3 have also been considered.