Agro Waste Derived Activated Carbon as a Catalyst in Red-2G Degradation Process Optimized by Definitive Screening Design Approach

Abstract

Red-2G is considered a non-biodegradable azo dye by United States environmental protection agency (EPA) as it is resistant against biological degradation. Here, a new method is presented to prepare activated carbon (ACP-850) using thermally treated pistachio nutshell and potassium oxalate as precursors to accelerate the dye degradation process with peroxymonosulfate (PMS) as oxidation agent. Having a high surface area (2318 m2 /g) and low-cost precursors, and the achievement of recyclable, biodegradable, and agricultural solid wastes are among the benefits of the proposed method. Also, the definitive-screening design approach is performed to evaluate the role of independent variables in degradation efficiency of PMS/ACP-850 system. Minitab response optimizer indicates the possibility of achieving a response value of 100% through the use of a factorial blend of PMS=3.0 mM, pH=3.0, ACP=1.0 g/L, and time= 80 min at room temperature for Red-2G concentration of 60 mg/L as optimum conditions. Furthermore, complete degradation of Red-2G with a higher concentration (170 mg/L) to H2O and CO2 as eco-friendly compounds occurs under following condition: PMS=6.0 mM, pH=3.0, ACP=2.0 g/L, and time= 180 min at a temperature of 55 °C,. Radical quenching experiments prove that sulfate anion radical (SO4 -• ) and superoxide anion radical (O2 • - )play key roles as reactive species in the PMS/ACP-850 system at acidic and basic conditions, respectively. Reusability investigation confirms that ACP-850 can be frequently utilized to degrade dye from the contaminated solution. The LC/MS/MS and UV-VIS spectrometry analysis results along with mineralization rate demonstrate the effective possibility of decomposing Red-2G by the PMS/ACP-850 system.