In this study, raw corn silk was considered for the removal of cadmium ions from aqueous solutions. In order to improve adsorption characteristics, the KOH treatment was applied as a route to obtain modified materials. Both materials before and after metal adsorption were characterized by pH_PZC, SEM-EDX and FTIR analysis. SEM images and FTIR spectra revealed that alkali modification caused some structural changes that could improve the adsorption properties of the investigated material. The experimental results and the ion-exchange study revealed that the biosorption process of cadmium ions on to raw and modified corn silk was caused predominantly by the ion-exchange mechanism, followed by chemisorption. The kinetic parameters implied that there are three stages in the biosorption process. In addition, the cadmium adsorption on both materials is very fast and is followed by the pseudo-second-order kinetic model. The experimental results were fitted by two and three parameter isotherm models, while the Sips isotherm model best describes the biosorption process on both materials. According to the Sips isotherm model, the maximum adsorption capacity of cadmium adsorbed on modified materials was 49.06 mg g⁻¹, which is 2.23 times greater in comparison to the raw material (21.96 mg g⁻¹). Furthermore, the mechanisms of cadmium adsorption onto the investigated materials are summarized in order to better understand the modification influence on the adsorption properties of corn silk. In order to examine reusability of the investigated material, diluted nitric acid was used for regeneration. A desorption study was performed in three adsorption-desorption cycles. A high desorption efficiency (˃85%) indicated that MCS after Cd adsorption can be efficiently recovered and reused for a new adsorption cycle.

In this paper, the character of structural changes induced by different mechanical treatments to Prunus persica stones (PSs), and its subsequent effect on biosorption kinetics of Cu(II) were investigated. PSs were processed in vibratory disk mill (PS-V) and ultra-centrifugal mill (PS-C) and characterized by XRD, BET, SEM and FTIR spectroscopy. It was shown that PS-V was smaller and more reactive with less crystallinity index and hydrogen bond intensity compared to PS-C. In opposite, surface area of the PS-C was bigger than that of the PS-V. The total pore volume was about threefold, while the volume of micro pores was 9.29 times higher in PS-Cs than in PS-Vs.The kinetics of Cu(II) biosorption by both PSs was tested through various kinetic models: pseudo-first and pseudo-second order rate equations, Elovich equation, Boyd model, Weber–Morris and Urano–Tachikawa intraparticle diffusion model. For both sample types, Cu(II) biosorption occurred through combination of intraparticle and film diffusion mechanism, while kinetic results were best described by the pseudo-second order kinetic model. At the same time, the results indicated that together with kinetic rate the biosorption capacity of PS-C (21.20mgg−1) was higher than that of PS-V (16.30mgg−1).Mechanical activation like crushing and grinding will change material particle size, specific surface area and porosity, as well as its crystallinity. However, this paper elucidates that such physical structural changes will impact on heavy metal ions removal efficiency. This investigation suggests that the type of size reduction in lignocellulosic biosorbent preparation plays a very important role in overall biosorption performance, so it should be carefully considered every time when the mechanical treatment of material is necessary to be applied