Minimizing adsorbent requirements using multi-stage batch adsorption for malachite green removal using microwave date-stone activated carbons

Microwave and thermal treatment methods have been applied in order to produce two derived active carbons using waste date pits/stones from a date syrup processing plant. The adsorption properties of the two products have been tested for the adsorption of the toxic Malachite Green dye, which is commonly applied in the textile and plastics industry. Equilibrium isotherms were determined by experiment and evaluated using six isotherm correlations. The optimum fitting correlation for the thermally treated product was the Langmuir-Freundlich isotherm and for the microwave product was the Redlich-Peterson. The surface areas of the thermal product and the microwave product were 669.3 m²/g and 1123 m²/g respectively; and maximum malachite green adsorption capacities were 58 mg/g and 98 mg/g respectively. A two-stage batch adsorber model has been developed to optimize the two-step adsorption process to adsorb malachite green and minimize the amount of adsorbent, and therefore adsorbent cost, used for both thermal treated and microwave treated date stones. The output applications include the minimum total adsorbent for designing various percentages dye removal based on various effluent discharge concentrations and various initial dye concentrations.