关键词: 印染废水, 离子型染料, 吸附处理, 多孔, TiO₂微粒, 重复利用性能

Abstract:

Objective The utilization rate of dyes is unable to reach 100% in practical situations, which inevitably leads to residual dyes in the water discharged after dyeing, causing serious water pollution. Therefore, it is necessary to develop a water treatment technology that can effectively treat dye wastewater. Aiming at the treatment of ionic dyes in printing and dyeing wastewater, porous titana (TiO₂) particles were used as adsorbent to adsorb dyes.

Method In addition to the characteristics of stable chemical properties, low price, easy availability, and no toxicity, TiO₂ particles also have the unique characteristic of photocatalysis. Therefore, TiO₂ particles are often adopted to adsorb and catalyze dyes in wastewater. Through photocatalysis, the dye can be degraded, so that the TiO₂ particles can be reused. With tetrabutyl orthotitanate as titanium source, porous TiO₂ particles with different potentials were prepared by hydrothermal method using different templates, and then the crystal form of TiO₂ particles was controlled by high-temperature calcination. The potential, morphology and crystal form of TiO₂ were analyzed by solid surface Zeta potential test, field emission scanning electron microscopy(FETEM), transmission electron microscopy(TEM) and X-ray diffraction (XRD). The dye concentration and adsorbent dosage were optimized by adsorption test, and the reuse performance of TiO₂ particles was explored.

Results Positively charged TiO₂ particles (G-TiO₂) adsorb anionic dyes only other than cationic dyes at all, while the negatively charged TiO₂ particles (Y-TiO₂) only adsorb cationic dyes other than anionic dyes (Fig. 3 and Fig. 4). The adsorption mechanism follows the electrostatic adsorption mechanism. G-TiO₂ has a porous spherical structure formed by the aggregation of numerous particles, about 93% of which are microspheres with a particle size of 200-500 nm. Y-TiO₂ is in the state of fine particle aggregation, and about 91% of which are microspheres with a particle size of 50-100 nm (Fig. 6 and Fig. 7). The crystal forms of the two kinds of TiO₂ particles after calcination are anatase, which have photocatalytic properties (Fig. 9). Under the same experimental conditions, the adsorption rate of 100 mg/L Congo Red dye by 100 mg G-TiO₂ can reach 99.5%, and that of 20 mg/L Methylene Blue dye by 100 mg Y-TiO₂ can reach 93.5% (Fig. 11). In the cycle experiment, the adsorption rate of Congo Red dye by G-TiO₂ decreased by about 12.6% after four cycles, while that of Methylene Blue dye by Y-TiO₂ decreased by about 17% after five cycles (Fig. 13).

Conclusion Two kinds of porous TiO₂ particles adsorbents were prepared by changing the type of template in the hydrothermal reaction. The adsorbents not only retain the capillary adsorption of conventional porous TiO₂ particles on dyes, but also increase the electrostatic adsorption, which can realize the rapid adsorption of ionic dyes in printing and dyeing wastewater. The adsorbents can be chemically modified subsequently to have improved photocatalytic performance, and can also be loaded on polymer films or nonwovens for specific applications. This study will provide strategic support for the treatment of ionic dye wastewater.

Key words: printing and dyeing wastewater, ionic dye, adsorption treatment, porous, titania microsphere, reuse