Color removal from water-based ink wastewater by bagasse fly ash, sawdust fly ash and activated carbon

Abstract

Bagasse fly ash (BGFA), sawdust fly ash (SDFA) and activated carbon (AC) were investigated for color removal from wastewater from the printing ink industry after coagulation of water-based ink wastewater. Synthetic water-based ink was used to study the adsorption isotherm. The maximum adsorption capacity of BGFA increased with temperatures, having values of 7.30, 12.67, 21.60 and 29.07 mg g −1 at 30, 40, 50 and 60 °C, respectively. At 30 °C the maximum adsorption capacity of BGFA increased from 7.30 to 14.34 mg g −1 when using water-washed BGFA. The Langmuir, Freundlich and Redlich–Peterson models were all able to explain the color removal of synthetic water-based ink by BGFA, water-washed SDFA (SDFA/W) and AC, whereas R 2 of these three models by SDFA was not high. It might be due to color removal by SDFA involved both precipitation and adsorption of the ink, whereas only adsorption was involved by SDFA/W, BGFA and AC. The synthetic water-based ink adsorption capacity at 30 °C was ranked as SDFA > AC > SDFA/W > BGFA with values of 85.47, 40.49, 30.21 and 7.30 mg g −1, respectively. The efficiencies of BGFA, SDFA and AC for color removal from wastewater from printing ink industry after water-based ink coagulation showed that color removal by SDFA (90%) was higher than commercial AC (80%), SDFA/W (76%) and BGFA (68%), respectively at the same dosage of 0.3% (w/v). The system pH was increased from 1.7 to around neutral by SDFA, while the system pH of AC, SDFA/W and BGFA was still low (pH ∼ 2–3). However, SDFA and BGFA had potential as alternative low-cost adsorbents for color removal of water-based ink wastewater from the printing ink industry.