Uptake of molybdate by adsorption onto industrial solid waste Fe(III)/Cr(III) hydroxide: kinetic and equilibrium studies

An Overview to Technical Solutions for Molybdenum Removal: Perspective from the Analysis of the Scientific Literature on Molybdenum and Drinking Water (1990–2019)

A bibliometric analysis using the Scopus database was performed to investigate the research documents published from 1990 to 2019 in scientific sources related to molybdenum in drinking water and determine the quantitative characteristics of the research in this period. The results from the analysis revealed that the number of publications was maintained at a regular production of around 5 papers per year until 2009, followed by a fast linear increase in the production in the period from 2010 to 2016 (29 papers in 2016), but the scientific production regarding this topic was reduced in 2017 and 2018 to recover the production obtained in 2016 once again in 2019. The total contribution of the three most productive countries (USA, China and India, respectively) accounted for around 50% of the total number of publications. Environmental Science was the most common subject (51.4% contribution), followed by Chemistry (26.7% contribution). The research efforts targeted toward the search for technical solutions for molybdenum removal from water are not as important as the ones focused on the identification of molybdenum-polluted water bodies and the analysis of the health effects of the intake of molybdenum. Nevertheless, examples of technological treatments to remove molybdenum from the aqueous solution include the use of adsorption and ion exchange; coagulation, flocculation and precipitation followed by filtration; membrane technologies and biological treatments.

A novel ionic liquid-impregnated chitosan application for separation and purification of fission 99Mo from alkaline solution

In this investigation, a novel application of Aliquat 336 (tricaprylmethylammonium chloride)-impregnated chitosan (AICS) for the separation and purification of 99Mo from some fission products, such as 137Cs, 85Sr and 131I, in alkaline solution is presented. Before impregnation, pristine chitosan experienced no adsorption affinity for Mo. However, this situation dramatically changed after the impregnation. The structure of AICS was elucidated by FTIR, SEM and EDX spectra. The influence of contact time, solution pH, weight of AICS, initial Mo concentration and temperature on the adsorption process was studied. Kinetic studies revealed that the rate of adsorption was impressively very fast and only 3 min were sufficient to reach equilibrium. The pH influence showed that Mo could be effectively adsorbed over a wide range of pH 3–11. The equilibrium data fitting to isotherms models followed the order Langmuir > Freundlich > Dubinin-Radushkevich. Based on the Langmuir model, the maximum adsorption capacity was computed at 60.1 mg/L. Thermodynamic studies indicated that the adsorption process is spontaneous and endothermic in nature. Finally, a pure solution of 99Mo with a purity >99 % was obtained from a real sample. The data obtained confirmed that AICS is a promising candidate for separation and purification of 99Mo from alkaline media.

Recycling of neodymium enhanced by functionalized magnetic ferrite

This study systematically evaluates Neodymium (Nd) recovery from actual seawaters and wastewater using functionalized magnetic ferrite (3-mercaptopropionic acid-tetraethyl orthosilicate ferrite, MPA-TEOS-ferrite). The recovery of Nd by MPA-TEOS-ferrite displayed an L-shaped nonlinear isotherm, suggesting limiting binding sites on the adsorbent surface. At room temperature, a significant recovery of Nd by MPA-TEOS-ferrite increased from 8.99% to 99.99% with increasing pH (2.89-8.16) and an enhanced maxima Nd recovery capacity was observed on MPA-TEOS-ferrite (25.58 mg/g) when compared with pure ferrite (22.27 mg/g). The L3-edge X-ray absorption near-edge structure (XANES) spectra for the adsorbents collected after Nd recovery indicated that Nd(III) was still the predominant oxidation species on the surface of MPA-TEOS-ferrite. Only slightly change in the oxidation state or electronic structure around the Nd ions could be found during the adsorption process. Importantly, no significant change was found on Nd recovery while the NaCl ionic strength increased from 0.01 to 0.5 N. Furthermore, the results also displayed that the synthesized MPA-TEOS-ferrite has a great potential in efficient and rapid recovery of Nd from seawaters and wastewater.

Rapid and efficient removal/recovery of molybdenum onto ZnFe2O4 nanoparticles

An efficient method for removing and recovering molybdenum (Mo) from water was developed by using ZnFe2O4 nanoparticles. The Mo adsorption displayed a nonlinear isotherm that fitted well with the Langmuir isotherm, showing limited adsorption sites on the surface of ZnFe2O4. The adsorption of Mo(VI) was dependent on solution pH. With increasing pH, the build-up of negative charges of both adsorbent and adsorbate led to enhanced electric repulsion between them. The K-edge XANES spectra for the adsorbents collected after Mo adsorption revealed that Mo(VI) was the predominant oxidation state sorbed on ZnFe2O4, indicating that the reduction of Mo(VI) did not occur on ZnFe2O4. The different peak positions of k-space and R-space shown in K-edge EXAFS spectra demonstrated that the adsorbed Mo could be bound on the surface or be slipped in the vacancy position of the ZnFe2O4 crystal. Importantly, Mo could be efficiently adsorbed from photoelectric industrial wastewater and these adsorbed Mo anions were rapidly replaced by OH(-) ions, implying the potential for Mo removing and recovering in industrial wastewater.