The content of Sb in one abandoned brake pad reached up to 1.62 × 104
mg/kg.
Effects of initial pH, temperature and four organic acids (acetic acid, oxalic acid, citric acid
and humic acid) on Sb release from brake pads were studied using batch reactors.
Approximately 30% (97 mg/L) of the total Sb contained in the brake pads was released in
alkaline aqueous solution and at higher temperature after 30 days of leaching. The organic
acids tested restrained Sb release, especially acetic acid and oxalic acid. The pH-dependent
concentration change of Sb in aqueous solution was best fitted by a logarithmic function. In
addition, Sb contained in topsoil from land where brake pads were discarded (average
9×103
mg/kg) was 3000 times that in uncontaminated soils (2.7 ± 1 mg/kg) in the same
areas. Because potentially high amounts of Sb may be released from brake pads, it is
important that producers and environmental authorities take precautions.