Feasibility analysis of color removal from textile dyeing wastewater in a fixed-bed column system by surfactant-modified zeolite (SMZ)

摘要

In this study, the ability of surfactant-modified zeolite (SMZ) to remove color from real textile wastewater was investigated. Tests were performed in a fixed-bed column reactor and the surface of natural zeolite was modified with a quaternary amine surfactant hexadecyltrimethylammonium bromide (HTAB). The zeolite bed that was modified at 1 gL~(-1) HTAB concentration and HTAB flow rate of 0.015 Lmin~(-1) showed good performance in removing color. Effects of wastewater color intensity, flow rates and bed heights were also studied. Wastewater was diluted several times in the ratios of 25%, 50% and 75% in order to assess the influence of wastewater strength. The breakthrough curves of the original and diluted wastew-aters are dispersed due to the fact that breakthrough came late at lower color intensities and saturation of the bed appeared faster at higher color intensities. The column had a 3-cm diameter and four different bed heights of 12.5,25,37.5 and 50cm, which treated 5.25,19.50,35.25 and 51 L original textile wastewater, respectively, at the breakthrough time at a flow rate of 0.025 Lmin~(-1). The theoretical service times evaluated from bed depth service time (BDST) approach for different column variables. The calculated and theoretical values of the exchange zone height were found with a difference of 27%. The various design parameters obtained from fixed-bed experimental studies showed good correlation with corresponding theoretical values, under different bed heights. The regeneration of the SMZ was also evaluated using a solution consisting of30gL~(-1)NaCland 1.5gL~(-1) NaOH at pH 12 and temperature 30℃ Twice-regenerated SMZ showed the best performance compared with the others while first- and thrice-regenerated perform lower than the original SMZ.