Toxicity assessment of pickling liquors containing TiF₃, HF and HCl before and after neutralization using a phytotesting method

Abstract

The paper evaluates the toxicity of spent acid pickling liquor (SAPL) formed in the production of titanium products during its etching with a mixture of hydrofluoric and hydrochloric acids. The SAPL contained TiF₃, HF and HCl in the amounts of 21,9 g/l, 1,7 g/l and 6,2 g/l, respectively. To determine the toxicity of SAPL, a phytotesting method was used. As a phytoecological indicator, cress of Zabava variety was used. The experiment was carried out according to the procedure for determining the toxicity of drinking, ground, surface and sewage water; the toxicity of chemical solutions by measuring the germination index, average length and average dry weight of seed germs of cress (Lepidium sativum). The toxicity of the SAPL was determined before and after neutralizing with alkali. It has been shown that SAPL has an acute toxic effect both before and after its neutralization by alkali. To determine a safe dilution rate, the influence of SAPL dilution on seed germination, average length and average dry weight of the seedlings was studied. It was found that the seedlings average length-dilution rate equations most reliably describe the experimental findings. The safe dilution rate calculated from these relations is 669,2 for non-neutralized SAPL and 382,5 for alkaline neutralized SAPL.