ABSTRACT This study demonstrates the usage of primarily discarded waste – pomegranate peel as secondary raw material – biosorbent for broader applications. The focus was on the optimisation of key cationic dye methylene blue (MB) – pomegranate peel (PP) adsorption process parameters, as well as cost analysis assessing the possibility of scaling up. The optimal values of the key parameters were pH 6, biosorbent mass 100 mg, contact time of 50 min, and initial analyte concentration 100 mg/L for MB removal from aqueous solutions providing high removal efficiency values > 88%. Fourier-transform infrared spectroscopy (FTIR) showed that MB adsorption on PP was presumably via hydrogen bonds with the OH groups present in PP. Changes noted via elemental composition analysis given by electron dispersive spectroscopy (EDS) confirmed the sorption of MB. Biosorption occurred mainly as a pseudo-second-order kinetic reaction combined with phase III of the intraparticle diffusion model (both R2 ≥ 0.92). Through a simple and fast batch MB sorption process with many advantages compared to literature data, a maximum sorption capacity of 384.61 mg/g could be achieved. Pomegranate peel was identified as a low-cost adsorbent with excellent potential for MB removal, economically viable (0.74 $/mol), demonstrating great possibilities for industrial application. Highlights Biosorption of phenothiazine dye on novel waste material from pomegranate peel in its native form. A univariate general procedure was performed, FTIR, SEM, and EDS characterisation of biosorbents. An optimal pH value was determined to be 6, while the optimal mass was 100 mg. A maximum biosorption capacity of 384.61 mg/g could be achieved. The mechanism of adsorption is best obeyed by the Langmuir and Freundlich models. The total analysis expenses for the entire procedure were just 0.74 $/mol. GRAPHICAL ABSTRACT

The issue of water contamination by heavy metal ions as highly persistent pollutants with harmful influence primarily on biological systems, even in trace levels, has become a great environmental concern globally. Therefore, there is a need for the use of highly sensitive techniques or preconcentration methods for the removal of heavy metal ions at trace levels. Thus, this research investigates a novel approach by examining the possibility of using pomegranate (Punica granatum) peel layered material for the simultaneous preconcentration of seven heavy metal ions; Cd(II), Co(II), Cr(III), Cu(II), Mn(II), Ni(II) and Pb(II) from aqueous solution and three river water samples. The quantification of the heavy metals was performed by the means of FAAS technique. The characterization of biomaterial was performed by SEM/EDS, FTIR analysis and pHpzc determination before and after the remediation process. The reusability study, as well as the influence of interfering ions (Ca, K, Mg, Na and Zn) were evaluated. The conditions of preconcentration by the column method included the optimization of solution pH (5); flow rate (1.5 mL/min), a dose of biosorbent (200 mg), type of the eluent (1 mol/L HNO3), sample volume (100 mL) and sorbent fraction (<0.25 mm). The biosorbent capacity ranged from 4.45 to 57.70 μmol/g for the investigated heavy metals. The practical relevance of this study is further extended by novel data regarding adsorbent cost analysis (17.49 $/mol). The Punica granatum sorbent represents a highly effective and economical biosorbent for the preconcentration of heavy metal ions for possible application in industrial sectors.

Various toxic heavy metals have become hazardous to human health as well as the environment. This research has been focused on a biosorption/bio-removal process of chromium (III), copper (II) and lead (II) ions from an aqueous solution by utilizing lignocellulosic biomass of Citrus limon peel (CLP) powder. CLP powder biomass was selected based on dietary fibre components having greater potential to remove target heavy metal ions in order to purify wastewater by following the eco-friendly biosorption method. At optimum conditions, the observed maximum removal efficiency of 97.47, 87.13 and 95.71% for Cr, Cu and Pb ions, respectively, was observed. An investigation has been made as a work of pH, CLP amount and temperature. The presented bio-removal processes by prepared CLP biosorbent manifested as a temperature-independent. Langmuir isotherm model was found an excellent fit of the isotherm data for tested systems with the calculated biosorption capacities of 111.11 (Cr), 76.92 (Cu) and 100.00 (Pb) mg/g. The positive ΔH values for selected target heavy metal ions, except lead ions, confirmed that the reaction was spontaneous and endothermic. A cooperative mechanism of second-order and intraparticle diffusion models during the adsorption processes of all three target ions was established with a higher coefficient of determination and more closely anticipated take-up (adsorption capacity). Furthermore, the interaction of -OH and -COOH functional groups of CLP that have a major role in the removal of Cr, Cu and Pb ions from single-ion aqueous solution and/or a surface biosorption was confirmed based on the results presented by SEM-EDS and FTIR analysis. Analysis from XRD revealed peak corresponding to amorphous cellulose type I as observed by FT-IR analysis.