Biosorption of Cr (III) from Polluted Water Using <i>Pennisetum</i> <i>clandestinum</i> Hochst (Kikuyo)

Given the abundance of kikuyu biomass resulting from the pruning of green areas, the aim of this study was to evaluate its use as a biosorbent (BK) for Cr (III) removal from polluted waters. The biomass was activated using H2SO4 (1.25%) and, NaOH (3.25%), and then characterized using Fourier-Transform Infrared Spectroscopy (FTIR) and, Scanning Electron Microscopy/Energy Dispersive Spectroscopy (SEM/EDS). The surface area was measured using the Brunauer-Emmett-Teller (BET) method. The adsorption process was carried out by employing a jar test, evaluating the adsorption capacity (q) as a function of biomass granulometry, dose (BK) and the pH of the solution. In addition, the kinetic process, BK regeneration and adsorption capacity on fur industry effluents were evaluated. Our results confirmed the presence of active groups on BK such as: –OH, -C=C-, -C=O, and -C-O-, with an increase of 1308.58% in specific surface area, as well as the presence of chromium. The three variables under study were significant and related in a mathematical model. Maximum adsorption capacities (qmax) of 47.9, and 37.6 mg/g were obtained when using synthetic waters and fur industry effluents, respectively. The pseudo-second-order kinetic model confirmed that the adsorption mechanism is chemisorption. Furthermore, it was possible to regenerate the BK at a pH of 3 with an adsorption capacity of 28.7 mg/g. The possibility of using kikuyu within the circular economy was demonstrated.