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

Natural clay minerals, because of their physical and chemical characteristics are good adsorbents of metals. Among metals we often investigate heavy metals, but redox-sensitive metals are getting more and more attention. Redox-sensitive elements were measured in clay pit samples from clay mine in Bosnia and Herzegovina. For the purpose of analysis, a 23 m deep clay pit core sample was taken. From this sample 45 clay pit subsamples from different depths were used. The pH, electrical conductivity (EC), oxidation-reduction potential (ORP) and redox-sensitive elements content were measured. Amounts of redox-sensitive metals and aluminum were measured with an ICP-OES instrument. For statistical evaluation, maximum, minimum, average, median, correlation, correlation applying Al normalization and clr transformation were calculated. When justified PCA analysis was performed. The results are showing acidic pH, and oxidative ORP. The EC varied significantly through the sediment. The element concentrations lie in the sequence: Fe>Ti>V>As. There is a significant change in correlations with and without Al-normalization. The highest difference in was found in case of titanium and vanadium (r value ranging from -0.553 to 0.835). Correlations and PCA after clr transformation showed mainly strong negative correlations, meaning that redox sensitive elements behave differently in clay samples. Supplementary material: https://doi.org/10.6084/m9.figshare.c.7014329