Comparison of strontium and calcium adsorption onto composite magnetic particles derived from Fe3O4 and bis(trimethoxysilylpropyl)amine

Cellulose- supported sulfated-magnetic biocomposite produced from hemp biomass: Effective removal of cationic dyes from aqueous solution

In present study, eco-friendly sulfated cellulose-magnetic biocomposite was successfully synthesized with a simple method from hemp biomass. ATR-FTIR was used to determine chemical changes, while FE-SEM-EDS, STEM, XRD, TG/DTA, and BET techniques were employed to identify changes in morphology, elemental composition, crystal structure, and thermal degradation. Moreover, the saturation magnetization and pHpzc values of the MSHB were also determined. The effectiveness of magnetic sulfated hemp biomass (MSHB) was tested in the removal of cationic dyes from wastewater, including methylene blue (MB), crystal violet (CV), and malachite green oxalate (MGO). The adsorption all three dyes to MSHB, the pseudo-second-order kinetic model and the Langmuir model were determined to be more appropriate, and was endothermic and spontaneous from thermodynamic parameters, too. The maximum MSHB adsorption capacities were found to be 457.6, 509.3, and 1300 mg/g for MB, CV, and MGO at 298 K. With increasing temperature, it also drastically increased in capacity. The outstanding property of the MSHB is that it shows high removal performance wide pH range, even after ten cycles its high removal efficiency is still over 96 % for all three dyes and almost unaffected from dense matrix medium. These results demonstrate that MSHB is remarkable adsorbent for removing cationic dyes.

Adsorption behaviour of tetrabromobisphenol A on sediments in Weihe River Basin in Northwest China

Tetrabromobisphenol A (TBBPA) is adsorbed on sediments in river environments, and various environmental factors have distinct effects on its adsorption behaviour. Investigating the adsorption behaviour of TBBPA on the sediments in Weihe River Basin is critical for protecting the water environment and providing a theoretical basis for the prevention and control of brominated flame retardant pollution. In this study, the adsorption behaviour of TBBPA on Weihe River sediment was investigated by conducting batch equilibrium experiments, and the effects of pH, dissolved organic matter, and ionic strength on the adsorption of TBBPA were discussed. The obtained results revealed that rapid adsorption was the main mechanism of the TBBPA kinetic adsorption process. The isothermal adsorption behaviour of TBBPA was well fitted by Freundlich model (R² 99.21%) than Langmuir model (R² 98.59%). The adsorption capacity for TBBPA is 34.13 mg/kg. The thermodynamic results revealed that the adsorption process of TBBPA by the sediment was a spontaneous endothermic reaction. The increase in pH and ionic strength inhibited the adsorption of sediments on TBBPA. With the increase in the humic acid concentration, the adsorption of TBBPA initially increased and subsequently decreased. Synchrotron radiation-Fourier transform infrared spectroscopy indicated that the adsorption mechanism of TBBPA on the surface of sediment was mainly π-π and hydrogen bonds. The obtained results are useful for understanding of TBBPA migration and transformation in river water bodies.

Synthesis of core-shell magnetic titanate nanofibers composite for the efficient removal of Sr(ii)

We report a facile approach for the fabrication of Fe₃O₄@titanate fibers magnetic composite through a hydrothermal method and sol-gel process. The structure and morphology were characterized by X-ray diffraction (XRD), transmission electron microsphere (TEM), scanning electron microscope (SEM) and energy-dispersive X-ray analysis (EDX). Owing to the high ion exchange capacity of the functional titanate layer, the obtained core-shell structured magnetic microspheres exhibited high removal efficiency towards strontium from wastewater. The effects of contact time and Sr(ii) concentration on the uptake amount of strontium were systematically investigated. The results indicated that the adsorption equilibrium can be reached within 30 min, and the maximum exchange capacity was approximately 37.1 mg g^-1. Moreover, the captured Sr(ii) can be eluted using 5 wt% of EDTA(Na), which contributed to the reduction of waste volume. Based on the experimental results of ion exchange process and X-ray photoelectron spectroscopy (XPS), a possible adsorption mechanism was proposed. This work provided a facile approach to synthesize magnetic functional nanocomposites for wastewater treatment.

Adsorption and removal of strontium in aqueous solution by synthetic hydroxyapatite

Hydroxyapatite (HAP) is a main mineral constituent of bone and tooth and has an outstanding biocompatibility. HAP is a possible sorbent for heavy metals in wastewater due to its high adsorption capacity and low water solubility. We developed a removal system of ⁹⁰Sr from aqueous solution by HAP column procedure. More than 90 % of ⁹⁰Sr was adsorbed and removed from the ⁹⁰Sr containing solution. Divalent cations, Ca²⁺, had little effect on the removal of ⁹⁰Sr up to a concentration of 1 mmol L⁻¹. This clearly indicates that the HAP column technique is advantageous with respect to the capacity to adsorb ⁹⁰Sr from water present in the environment.

Effect of adsorbents and chemical treatments on the removal of strontium from aqueous solutions

In the present investigation, three different solid wastes namely almond green hull, eggplant hull, and moss were initially treated and used as adsorbents for the adsorption of strontium ion from aqueous solutions. Adsorbent types and chemical treatments are proved to have effective roles on the adsorption of Sr(II) ion. Among the three adsorbents, almond green hull demonstrated strong affinity toward strontium ion in different solutions. The effectiveness of this new adsorbent was studied in batch adsorption mode under a variety of experimental conditions such as: different chemical treatments, various amounts of adsorbent, and initial metal-ion concentration. The optimum doses of adsorbent for the maximum Sr(II) adsorption were found to be 0.2 and 0.3 g for 45 and 102 mg L(-1) solutions, respectively. High Sr(II) adsorption efficiencies were achieved only in the first 3 min of adsorbent's contact time. The kinetics of Sr(II) adsorption on almond green hull was also examined and it was observed that it follows the pseudo second-order behavior. Both Langmuir and Freundlich models well predicted the experimental adsorption isotherm data. The maximum adsorption capacity on almond green hull was found to be 116.3 mg g(-1). The present study also confirmed that these low cost agriculture byproducts could be used as efficient adsorbents for the removal of strontium from wastewater streams.