Rheological Characteristics of Aqueous Ca-Bentonite Dispersions

607-615The rheological properties of Ca-bentonite suspensions in different volume concentrations have been studied as a function of pH and the concentraiton of added electrolytes. In addition, the conductance of suspensions was determined. The flow behaviour of suspensions with and without containing electrolytes fitted the Bingham plastic flow. The yield stress of suspensions, showed that the transition process from viscous flow to plastic flow required relatively high shear stress for the given volume concentrations. The suspension exhibited a shear-thinning behaviour in their native pH conditions. Below the pH value of 3, the stability of edge to face contact decreased. Apparent viscosity (ηa) values of suspensions were strongly pH dependent as plastic viscosity (ηp) values were nearly constant in the selected pH conditions. Apparent viscosity of suspensions exhibited different behaviour depending on the type of electrolytes. Although the highest increase in the specific conductivity was obtained with large amount of KCl addition, in case of NaCl addition, specific conductivity was increased largely more than in the KCl addition with increasing volume concentrations

Use of banana peel for the removal of boron from aqueous solutions in the batch adsorption system

In this study, the use of banana peels (BP) as a biosorbent which is considered agricultural waste for boron adsorption was investigated. The important operating parameters (pH, biosorbent dose, and contact time) affecting the batch adsorption system were examined. As a result of the conducted experiments, it was determined that the BP dose was 2 g/L, the initial pH was 6.07, and the contact time was 30 min. The maximum boron removal efficiency was achieved at approximately 66% under these conditions. In addition, different isotherms and kinetics were applied in this study. The R2 values of the pseudo-second-order kinetic model and the Freundlich isotherm were determined as 0.9694 and 0.9703, respectively. The maximum adsorption capacity of BP was calculated as 3.40 mg/g according to isotherms. SEM and FTIR analyses were performed to reveal the morphological and functional status of BP. The BP has a non-homogeneous macropores surface and predominantly hydroxyl (–OH), carboxyl (C–C), and amine (N–H) groups. As a result of the study, it was revealed that BP was an environmentally friendly, economical, and easily available biosorbent for boron removal. Graphical abstract: [Figure not available: see fulltext.]