Dehydrate Sewage Sludge as an Efficient Adsorbent for Malachite Green Removal in Textile Wastewater: Experimental and Theoretical Studies

We present in this study a simple approach on the application of dried dewatered sewage sludge (D@DSS) generated from a local wastewater treatment plant (WWTP). The D@DSS can be considered as an alternative friendly and cost-effective adsorbent for malachite green (MG) dye removal from an aqueous solution using batch systems. This procedure did not require any modification of the adsorbent characteristics. D@DSS demonstrated an excellent retention capacity for MG at synthetic solutions, and in industrial wastewater. Moreover, the selectivity study of the adsorbent was performed against Methylene Blue and Red Congo shows better capability of this adsorbent towards cationic dyes. The D@DSS adsorbent characterization was carried-out using SEM, FTIR, Zeta potential, XRD and ICP. The results confirmed a rough and charged surface of the adsorbent with the presence of specific functional groups. The adsorption process fits well with the Jovanovic model isotherm and was adhered to the pseudo-second order kinetics. The process conditions were optimized using the response surface methodology, resulting in qe (78.10 mg g−1) for different values of the input variables, including pH (10), ionic strength (0.015 mg g−1), initial concentration (150 mg g−1), temperature (37.29 °C),contact time (58.25 min), adsorbent dose (0.05 g) and particle size (0.203 mm). Hence, the proposed D@DSS can be effectively applied as a low-cost adsorbent for MG elimination from different contaminated water samples and can be easily extended to remove other cationic dyes.