Display omitted •Tannery sludge was used as carbon precursor for preparation of activated carbon.•The pyrolysis step was carried out using microwave heating.•Adsorption of AB-210 and AR-357 dyes was studied using AMWCTS as adsorbent.•The Qmax values of AB-210 and AR-357 are 1108 and 589.5mgg−1, respectively.•AMWCTS is effective for treatment of simulated dye effluents. An activated carbon was prepared by chemical activation of the sludge collected from tannery wastewater treatment plant (TWTP) using microwave heating. The sludge was mixed with ZnCl2 and lime to form a paste, which was inserted inside a quartz reactor and irradiated by microwave for 10min under N2. After the pyrolysis, the carbonized material was refluxed with a 6.0molL−1 HCl to obtain the activated carbon (AMWCTS). The AMWCTS was characterized by SEM, FTIR, TGA, XRD, BET and BJH analytical techniques. AMWCTS has high BET surface area of 491.0m2g−1 and total pore volume of 0.440cm3g−1 with mesoporous pore size distribution. The studies of pH, kinetic and equilibrium for adsorption of Acid Black 210 (AB-210) and Acid Red 357 (AR-357) leather dyes onto AMWCTS were investigated at 298K. The kinetic data were best fitted to the Avrami kinetic model. The maximum sorption capacities of AMWCTS for AR-357 and AB-210 are 589.5 and 1108mgg−1, respectively. Finally, the AMWCTS was tested using simulated effluents (complex mixture of dyes), obtaining an adsorption efficiency of at least 93.79%, showing the potentiality of AMWCTS as adsorbent for treatment real effluents.