Enhanced removal of ammonium from the aqueous solution using a high-gravity rotating packed bed loaded with clinoptilolite

Removal of Ammonium Ions from Aqueous Solutions Using Weathered Halloysite

This study investigated the use of weathered halloysite as an ion exchange material for ammonium removal from water. The study was conducted under static and dynamic conditions. The influence of such parameters as the preliminary concentration of ammonium ions, dose of halloysite, and pH was examined in periodic studies. The ion exchange capacity of weathered halloysite under various regeneration conditions such as concentration, excess of regeneration solution and the pH at which the regeneration was performed was also determined. The effect of flow velocity, initial NH₄⁺-ions concentration was studied in column tests and the weathered halloysite’s ion -exchange capacity was also determined. The best results of ammonium ion removal were obtained at pH 6. The equilibrium isotherms were described using the Langmuir and Freundlich models. The results of periodic studies show a good fit for the data of both models, with Langmuir isotherms reflecting the removal of ammonium ions better. A good match for the data (R² > 0.99) was provided by a pseudo second-order kinetic model. The obtained results indicate that a properly prepared halloysite can be a useful mineral for the removal of dangerous substances, such as ammonium ions, present in natural waters.

Kinetic Studies of Cs+ and Sr2+ Ion Exchange Using Clinoptilolite in Static Columns and an Agitated Tubular Reactor (ATR)

Natural clinoptilolite was studied to assess its performance in removing caesium and strontium ions, using both static columns and an agitated tube reactor (ATR) for process intensification. Kinetic breakthrough curves were fitted using the Thomas and Modified Dose Response (MDR) models. In the static columns, the clinoptilolite adsorption capacity (qe) for 200 ppm ion concentrations was found to be ~171 and 16 mg/g for caesium and strontium, respectively, highlighting the poor material ability to exchange strontium. Reducing the concentration of strontium to 100 ppm, however, led to a higher strontium qe of ~48 mg/g (close to the maximum adsorption capacity). Conversely, halving the column residence time to 15 min decreased the qe for 100 ppm strontium solutions to 13–14 mg/g. All the kinetic breakthrough data correlated well with the maximum adsorption capacities found in previous batch studies, where, in particular, the influence of concentration on the slow uptake kinetics of strontium was evidenced. For the ATR studies, two column lengths were investigated (of 25 and 34 cm) with the clinoptilolite embedded directly into the agitator bar. The 34 cm-length system significantly outperformed the static vertical columns, where the adsorption capacity and breakthrough time were enhanced by ~30%, which was assumed to be due to the heightened kinetics from shear mixing. Critically, the increase in performance was achieved with a relative process flow rate over twice that of the static columns.

Hydrothermal conversion of waste cartons into a magnetic carbon-iron composite for use as an efficient and recyclable dye adsorbent

Disposal of large quantities of waste cartons aggravates the burden of municipal solid waste treatment. Exploitation of the potential value of waste cartons and conversion of this waste stream into available materials is a hot research topic with practical application prospects. In this study, we successfully fabricated a magnetic carbon-iron composite from waste cartons via hydrothermal treatment and investigated its application as an efficient adsorbent for the removal of a disperse blue dye (DB 56) and reactive yellow dye (RY 3) from aqueous solution. The fabricated product was characterized by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and Brunauer-Emmett-Teller analysis. The effects of the composite dose, initial dye concentration, and solution pH on the dye removal efficiency were investigated. Under acidic conditions at pH 2, the removal efficiencies of DB 56 and RY 3 reached 81.53% and 96.77%, respectively. The adsorption processes followed pseudo-second-order kinetics and the Freundlich isotherm. The magnetic carbon-iron composite could be easily separated from the aqueous solution because of its magnetism, and could be regenerated by the Fenton reaction. After re-use in three cycles, the removal efficiencies for both dyes were still above 70%. The magnetic carbon-iron composite produced from waste cartons shows promise for application to effluent that contains dyes because of its low cost, high efficiency, and simple application.