Removal of Malachite Green Micro-pollutant from Wastewater using Circular Economy based Agricultural Solid Wastes

Water and wastewater treatment using adsorption technology based on solid wastes obtained from agricultural activities which are inexpensive and locally accessible have confirmed good adsorption performances for abstraction of malachite green (MG) dye micro-pollutant. Thus, this work reports low-cost and locally available Anchote peel (AP) and coffee husk (CH) untreated adsorbents for the elimination of MG from model wastewater. After characterizing the adsorbents by using Fourier infrared and x-ray powder diffraction spectrophotometers, the maximum dye removal efficiency at the optimum experimental settings: solution pH, dye initial concentration and temperature, equilibrium contact time, amount of adsorbent, and temperature) was determined to be 98.33% for AP and 98.11% for CH, respectively. The experimental results best agree with the Langmuir adsorption isotherms and pseudo-second-order kinetic models confirming that the uptake of MG involves of chemical processes to form monolayer followed by multilayer on the heterogeneous surface of the AP and CH adsorbents. Furthermore, the MG adsorption onto AP and CH is thermodynamically feasible, spontaneous, and non-uniform showing that there was surface change during adsorption. These adsorbents are cheap, abundant, environment benign and biodegradable. Lastly, it was inferred that the AP and CH agronomic solid wastes based adsorbents are promising sustainable functional materials with due adsorption capabilities for elimination of MG dye from aqueous solution.