Potency of Mixed Carcinogenic Dye Decolorization from Aqueous Solution by a Novel Thiocarbohydrazone Derived from 4-Hydroxy-6-Methyl-2,5-Dioxo-2H-Pyrano[3,2-c]Quinoline-3-Carboxaldehyde

Abstract The new adsorbent thiocarbohydrazone ( PQMT, 2 ) was synthesized by condensation reaction of 5,6-dihydro-4-hydroxy-6-methyl-2,5-dioxo-2 H -pyrano[3,2- c ]quinoline-3-carboxaldehyde ( 1 ) with thiocarbohydrazide. The structure of PQMT was deduced based on the elemental and spectral data (IR, 1 H NMR, 13 C NMR and mass spectra). The PQMT adsorbent was extra characterized by XRD, SEM, SEM–EDS mapping, N 2 -adsorption–desorption isotherm, S BET , Pore size distribution and zeta potential studies. The results reflected a notable enhancement in the surface meso-porosity, total pore volume, crystallinity, S BET = 68.37 m 2 / g, and the pH zpc was 7.1 for the new adsorbent. Water contamination constitutes a significant environmental challenge to the progress of human civilization. To contribute to solving this problem, the current compound was tested for its ability to decolorize sole, binary and ternary mixtures of methylene blue (MB), maxilon blue (MxB), malachite green (MG), remazole red (RR) and congo red (CR) dyes from an aqueous solution. Additionally, the effects of pH, contact time, initial dye concentration and temperature on the adsorption of MB and CR onto PQMT were investigated. The experimental studies showed that the removal percentages of single cationic and anionic dyes grew in the following order: RR < CR < MG < MB < MxB. Overall, this work highlighted that the PQMT adsorbent acts as a powerful adsorbent (100%) at a tiny contact time for decolorizing of both single and mixed cationic organic dyes (2–30 min., 10 ppm dye concentration, pH = 7.5 and temperature = 25 ºC) from aqueous solutions. In the binary system of the CR and MB dye system, the PQMT adsorbent exhibits considerable capacity and selectivity for the adsorption of MB in the presence of CR. The MB and CR dyes adsorption experimental data were well-fitted by Langmuir isotherm and pseudo-second order kinetic models. Under optimal conditions (m = 50 mg, pH = 7.5, dye conc. 10 ppm and V = 100 mL), the adsorption capacity of PQMT for MB was 36.6 mg/g, and for CR (m = 50 mg, pH = 3, dye conc. 10 ppm and V = 100 mL)), it was 91.7 mg/g. The calculated thermodynamic parameters reflected a spontaneous and endothermic adsorption reaction. The decolorization interaction mechanisms between the MB dye and the PQMT adsorbent were experimentally and theoretically studied in detail.