Color removal from anaerobic/aerobic treatment effluent of bakery yeast wastewater by polyaniline/beidellite composite materials

• A cost effective adsorbent was proposed for the color removal from baker yeast wastewater.
• The removal efficiency of the adsorbent was studied over a wide pH range (2–10).
• The optimum color and TOC removal were 88.7% and 63.3%.
• The removal mechanism by using PAn + Bei composite material seemed to mostly occur via an anion exchange process.
• The PAn + Bei composite material preferentially removed the lower molecular weight components.

The adsorption technique is widely applied for the removal of pollutants from wastewater, especially for toxic or non-biodegradable wastewater. In recent years, the production of alternative adsorbents to replace costly adsorbents has been paid more attention to in literature. Polyaniline/beidellite (PAn + Bei) composite material as an absorbent, which is efficient and low cost can easily be prepared via H2SO4, KIO3 and aniline. This paper deals with color and total organic carbon (TOC) removal of biologically treated bakery yeast wastewater (BYW) using the PAn + Bei composite material by adsorption processes. The effects of experimental variables were chosen as the initial pH (pHi), sorbent dosage (ms), contact time (tc) and mixing speed (s) by a batch sorption process. It was found that by increasing the adsorbent dosage (0.025–0.400 g/50 ml of composite dosage), contact time (2–240 min) and decreasing the pHi (9–3) improved the color and TOC removal efficiencies. The optimum color and TOC removal efficiencies were obtained as 88.7% and 63.3% at 0.400 g/50 ml of adsorbent dosage, a pHi of 3, 240 rpm, and 240 min. In addition, a pseudo-second order kinetic model was proposed to correlate the experimental data. To understand the removal mechanism and characterize the surface of the PAn + Bei composite material, size exclusion chromatography (SEC), BET surface analysis, fourier transform infrared spectroscopy (FTIR) analysis, scanning electron microscope (SEM), thermal gravimetric analysis (TGA), and differential scanning calorimetry (DSC) were employed. As a consequence, the proposed mechanism for the removal by PAn+Bei composite material seems to be driven by an ion exchange process.