XXI Century. Technosphere Safety

Liquid waste from paint and varnish production—consisting of spent organic solvents, washing liquids, and off-spec products—is a large-volume, toxic waste stream. Incineration or landfilling of such waste leads to the irreversible loss of valuable secondary resources and causes significant environmental harm. This study aims to provide experimental justification for the feasibility of recovering target components from this waste via rectification distillation, enabling their return to the production cycle. Samples of liquid waste were collected from an industrial paint and varnish plant in Irkutsk. The primary processing method employed was fractional distillation using a rectification packing. Experiments were carried out with a laboratory setup comprising a distillation flask, a rectification column (with an efficiency of five theoretical plates), a reflux condenser, and a fraction collection unit. The process was conducted at atmospheric pressure over a temperature range of 60–180 °C. The initial composition and the quality of the resulting fractions were analyzed using gas chromatography–mass spectrometry (GC–MS) and IR spectroscopy. The main components of the raw waste were found to be toluene (25–30 %), xylenes (20–25 %), ethylbenzene (8–10 %), butanol (5–7 %), acetone (3–5 %), as well as resinous substances and suspended pigment particles (up to 15 %). By optimizing the distillation conditions (flask heating rate of 1–2 °C/min, reflux ratio of 3–4), three main marketable fractions were obtained: a low-boiling fraction  (b.t. 56–68 °C), consisting mainly of acetone and ethyl acetate; a medium-boiling fraction (b.t. 100–120 °C), containing toluene and butanol; and a high-boiling fraction (b.t. 135–155 °C), a mixture of xylenes and ethylbenzene. The recovery yield of the total aromatic hydrocarbon fraction, suitable for reuse as a solvent, reached 71.5 % of the initial waste mass. The purity of the isolated toluene concentrate exceeded 92 %, meeting the technical specifications for Grade A. The still bottoms (≈25 % of the mass) consisted of a concentrated resin with a high content of non-volatile components. The results demonstrate the feasibility and high efficiency of rectification distillation for processing liquid paint and varnish waste to recover valuable organic solvents. When implemented at industrial plants, this technology can reduce the environmental burden by decreasing the volume of landfilled waste while also providing economic benefits through the substitution of primary solvents with recycled ones. Further research should focus on developing a processing method for the still bottoms.