Removal of cobalt and strontium from groundwater by sorption onto fishbone

Treatment of produced water using Mn oxide nanoparticales loaded on walnut shells

Sorption of ²²⁶Ra from produced water with oil production on manganese oxide nanoparticles loaded on walnut shell media was investigated using batch-type technique. The results showed that ²²⁶Ra is effectively adsorbed onto the adsorbent with equilibrium time of approximately 30 min. Removal efficiency of ²²⁶Ra from produced water depends mainly on the adsorbent dose and concentration of associated ions; removal efficiency decreased when their concentrations increase. The maximum adsorption capacity is reached 58 Bq g^-1. The adsorbent is effective and suitable for removing ²²⁶Ra ions from the produced water under the studied conditions in this work.

The Influence of Salinity on the Removal of Ni and Zn by Sorption onto Iron Oxide- and Manganese Oxide-Coated Sand

The influence of salinity on the single and binary sorption of Ni and Zn onto iron oxide- and manganese oxide-coated sand (IOCS and MOCS) was investigated at pH = 5. The single sorption experimental data were fitted to Freundlich, Langmuir, Dubinin–Radushkevich, and Sips models, and a nonlinear sorption isotherm was observed (NF = 0.309–0.567). The higher Brunauer–Emmett–Teller (BET) surface area (ABET) and cation exchange capacity (CEC) of MOCS contributed to the higher maximum sorption capacities (qmL) of Ni and Zn than that of IOCS. The Ni sorption capacities in the single sorption were higher than that in the binary sorption, while the Zn sorption capacities in the single sorption were less than that in the binary sorption. The single and binary sorptions onto both IOCS and MOCS were affected by the salinity, as indicated by the decrease in sorption capacities. Satisfactory predictions were shown by the binary sorption model fitting including P-factor, ideal adsorbed solution theory (IAST)–Freundlich, IAST–Langmuir, and IAST–Sips; among these, the P-factor model showed the best fitting results in predicting the influence of salinity of Ni and Zn in the binary sorption system onto IOCS and MOCS. IOCS and MOCS offer a sustainable reactive media in a permeable reactive barrier (PRB) for removing Ni and Zn in the presence of salinity.

Amidoxime Functionalization of Algal/Polyethyleneimine Beads for the Sorption of Sr(II) from Aqueous Solutions

There is a need for developing new sorbents that incorporate renewable resources for the treatment of metal-containing solutions. Algal-polyethyleneimine beads (APEI) (reinforced with alginate) are functionalized by grafting amidoxime groups (AO-APEI). Physicochemical characteristics of the new material are characterized using FTIR, XPS, TGA, SEM, SEM-EDX, and BET. AO-APEI beads are tested for the recovery of Sr(II) from synthetic solutions after pH optimization (≈ pH 6). Uptake kinetics is fast (equilibrium ≈ 60-90 min). Sorption isotherm (fitted by the Langmuir equation) shows remarkable sorption capacity (≈ 189 mg Sr g-1). Sr(II) is desorbed using 0.2 M HCl/0.5 M CaCl2 solution; sorbent recycling over five cycles shows high stability in terms of sorption/desorption performances. The presence of competitor cations is studied in relation to the pH; the selectivity for Sr(II) is correlated to the softness parameter. Finally, the recovery of Sr(II) is carried out in complex solutions (seawater samples): AO-APEI is remarkably selective over highly concentrated metal cations such as Na(I), K(I), Mg(II), and Ca(II), with weaker selectivity over B(I) and As(V). AO-APEI appears to be a promising material for selective recovery of strontium from complex solutions (including seawater).

Evaluation of hydroxyapatite/poly(acrylamide-acrylic acid) for sorptive removal of strontium ions from aqueous solution

A composite polymer, hydroxyapatite/poly(acrylamide-acrylic acid), was synthesized by gamma-induced polymerization. The factors affecting the sorption process were evaluated. The removal increased with time and achieved equilibrium after 1 h for all initial concentration ranges (10-50 mg/L). The highest removal of Sr(II) was achieved using 50 mg/L at pH 6. The sorption process was found to follow a pseudo-first-order mechanism. The equilibrium data are best described by the Langmuir model, with a monolayer capacity of 53.59 mg/g. The values of thermodynamic parameters indicate that the sorption process is endothermic (ΔH > 0), increases randomness (ΔS > 0) and is spontaneous (ΔG < 0). The results imply that the composite could be used as a promising low-cost material for the removal of radionuclides from radioactive waste.

Feasibility of using natural mineral ores for removing Cs and Sr from contaminated water

Proper and economical treatments of wastewater are among the important and potential solutions to increase the water budget. Although mineral ores are barriers of potentially toxic metal contaminants; however to what extent, can these ores stand successfully for decontaminating waters polluted with Cs or Sr is the question of the current study. Therefore a trial was carried out on some of these ores i.e. kaolinite, montmorillonite, and illite, to investigate their effects as decontaminants for waters polluted with either 50 μg Cs L^-1 or 50 μg Sr L^-1. Results showed that sorption of Cs and Sr increased with decreasing the ratio of the applied sorbents to the quantities of contaminated waters. Such a finding was more obvious when the rate of the sorbent: water was only 1 g L^-1. The highest sorption was attained by montmorillonite followed by kaolinite, then Illite. Thus, montmorillonite was selected to complete the sorption studies at a rate of 1 g L^-1. Sorption of both Cs and Sr and consequently their removal efficiencies increased with increasing the pH of the sorbents-contaminated waters suspensions up to 7 beyond which significant reductions occurred. Also, increasing the temperature of the suspension resulted in significant increases in the removal efficiencies of the investigated sorbents. Only 120 min were enough to attain the highest removal efficiency. Moreover, Ca-salts could successfully substitute sorbed Cs and Sr on surfaces of the montmorillonite used previously for decontamination of these elements from waters. Accordingly, this mineral ore can be reused successively for further decontamination processes.

Sorption of divalent heavy metal ions onto functionalized biogenic hydroxyapatite with caffeic acid and 3,4-dihydroxybenzoic acid

The sorption ability of biogenic hydroxyapatite (BHAP) towards heavy metal ions (Pb, Cu, Ni, Cd, and Zn) is compared with functionalized BHAP powders with caffeic acid (CA) and 3,4-dihydroxybenzoic acid (3,4-DHBA). The functionalization of the BHAP with either CA or 3,4-DHBA is indicated by the appearance of the colored powders due to the formation of the interfacial charge transfer (ICT) complexes. The detailed characterization of as-prepared and functionalized BHAP samples was performed using transmission electron microscopy, reflection spectroscopy, thermogravimetric analysis and determination of zeta potential. All three sorbents clearly displayed preferential sorption of Pb ions when the total concentration of multi-component equimolar solutions of heavy metal ions is high. It should be emphasized that the sorption capacity of functionalized BHAP with either CA or 3,4-BHAP was found to be higher, up to 60%, compared to as-prepared BHAP without the decrease of selectivity towards Pb ions.

A facile synthesis of hydroxyapatite for effective removal strontium ion

Hydroxyapatite (HA) with perforated porous structure was successfully synthesized using shell powder as the raw material by double interfacial diffusion method. The structure of obtained products was examined by X-ray diffraction, Fourier transform infrared spectrograph, field-emission scanning electron microscopy, transmission electron microscopy, particle size, thermogravimetry and nitrogen adsorption-desorption analysis etc. Results indicate that the perforated porous structure is composed of nanosheets and has high specific surface area (up to 188.5 m² g^-1). Thus, investigation of adsorbing Sr²⁺ in solution was further examined by discussing factors such as initial pH, ion strength, adsorbent dosage, contact time, initial Sr²⁺ concentration and temperature. The kinetics and equilibrium adsorption data followed the nonlinear pseudo-second-order kinetic and Liu isotherm models. The maximum removal (%) was up to 98.94% at 313.15 K, and the adsorption process of Sr²⁺ was endothermic, feasible, and spontaneous in nature as studied via thermodynamic analysis (ΔG° < 0, ΔH° > 0, and ΔS° > 0). A possible adsorption mechanism was proposed. Meanwhile, leaching and desorption experiments was used to evaluate recycling capacity. All the outcomes effectively reveal that the synthesized HA shows great potential in removing Sr²⁺ from nuclear effluents.

Comparison of sustainable biosorbents and ion-exchange resins to remove Sr2+ from simulant nuclear wastewater: Batch, dynamic and mechanism studies

Removal of Sr²⁺ from aqueous media presents particular challenges, especially in complex wastes such as nuclear industry liquors. Commercial sorbents while effective, can be highly expensive and subject to negative effects from competing ions. Here we evaluate two potential biosorbents (crab carapace and spent distillery grain) as potential alternatives and compare their performance to two commercial sorbents for Sr²⁺ removal at industrially relevant concentrations (low mg/L). Physical and structural characterization of the materials was undertaken, and batch and dynamic studies were performed on Sr²⁺ solutions and simulated nuclear wastewater. Sorption performance was quantified with respect to contact time, initial concentration and ion-competition. Removal efficiencies were 20-70% for the biosorbents compared to 55-95% for the commercial materials. Results indicated sorption was predominantly through monolayer coverage on homogenous sites and could be described using a pseudo-second-order kinetic model. Studies with the simulant liquor showed Sr²⁺ sorption was reduced by 10-40% due to ion-competition for sites. Characterization of biosorbents before and after Sr²⁺ sorption suggested that outer-sphere complexation and ion-exchange were the primary Sr²⁺ removal mechanisms. The efficiency of crab carapace for Sr²⁺ removal from aqueous media (with adsorption capacity 3.92 mg/g.) at industrially relevant concentrations, together with its mechanical stability, implementation and disposal cost, makes it a competitive option compared to other biosorbents and commercial materials reported in the literature.

The use of sea shell (Donax trunculus) powder to remove Sr(II) ions from aqueous solutions

This study aimed to investigate and explore the possibility of using ground sea shell powder (Donax trunculus) (SSP) for sorption of Sr(II) ions from aqueous solutions. The maximum removal of Sr(II) removal in SSP was 60% at initial Sr(II) concentration of 25 mg/L, at pH 6.0, contact time 120 min, temperature 25 °C and volume/mass ratio equivalent to 500. Sorption data were interpreted considering the adsorption isotherms and thermodynamic parameters calculated. The maximum Sr(II) adsorption on SSP was 25.45 mg/g at pH 6.0. Freundlich isotherm and Dubinin-Radushkevich models were seen to be more compatible with the sorption equilibrium. The nature of the process was spontaneous and exothermic. The results suggest that SSP could be used as an efficient and cost-effective adsorbent to remove strontium ion.

Effect of experimental variables onto Co(2+) and Sr(2+) sorption behavior in red mud-water suspensions

The prospects of rinsed red mud (alumina production residue) utilization for liquid radioactive waste treatment have been investigated, with Co(2+) and Sr(2+) as model cations of radioactive elements. To evaluate the sorption effectiveness and corresponding binding mechanisms, the process was analyzed in batch conditions, by varying experimental conditions (pH, Co(2+) and Sr(2+) concentrations in single solutions and binary mixtures, contact time, and the concentration of competing cations and ligands common in liquid radioactive waste). Comparison of the Co(2+) and Sr(2+) sorption pH edges with the red mud isoelectric point has revealed that Co(2+) removal took place at both positive and negative red mud surface, while Sr(2+) sorption abruptly increased when the surface became negatively charged. The increase of initial cation content and pH resulted in increased equilibrium times and sorption capacity and decreased rate constants. From single metal solutions and various binary mixtures, Co(2+) was sorbed more efficiently and selectively than Sr(2+). While Sr(2+) sorption was reduced by coexisting cations in the order Al(3+) ≥ Ca(2+) >Na(+) ≥Cs(+), removal of Co(2+) was affected by Al(3+) species and complexing agents (EDTA and citrate). Desorption of Co(2+) was negligible in Ca(2+) and Sr(2+) containing media and in solutions with initial pH 4-7. Sr(2+) desorption was generally more pronounced, especially at low pH and in the presence of Co(2+). Collected macroscopic data signify that Co(2+) sorption by red mud minerals occurred via strong chemical bonds, while Sr(2+) was retained mainly by weaker ion-exchange or electrostatic interactions. Results indicate that the rinsed red mud represent an efficient, low-cost sorbent for Co(2+) and Sr(2+) immobilization.