Biosorption of neodymium on Chlorella vulgaris in aqueous solution obtained from hard disk drive magnets

Abstract

In recent years, biosorption is being considered as an environmental friendly technology for the recovery of rare earth metals (REE). This study investigates the optimal conditions for the biosorption of neodymium (Nd) from an aqueous solution derived from hard drive disk magnets using green microalgae (Chlorella vulgaris). The parameters considered include solution pH, temperature and biosorbent dosage. Best-fit equilibrium as well as kinetic biosorption models were also developed. At the optimal pH of 5, the maximum experimental Nd uptakes at 21, 35 and 50°C and an initial Nd concentration of 250 mg/L were 126.13, 157.40 and 77.10 mg/g, respectively. Analysis of the optimal equilibrium sorption data showed that the data fitted well (R2 = 0.98) to the Langmuir isotherm model, with maximum monolayer coverage capacity (qmax) of 188.68 mg/g, and Langmuir isotherm constant (KL) of 0.029 L/mg. The corresponding separation factor (RL) is 0.12 indicating that the equilibrium sorption was favorable. The sorption kinetics of Nd ion follows well a pseudo-second order model (R2>0.99), even at low initial concentrations. These results show that Chlorella vulgaris has greater biosorption affinity for Nd than activated carbon and other algae types such as: A. Gracilis, Sargassum sp. and A. Densus.

Essential and toxic elements in commercial microalgal food supplements

“…Interestingly, some REEs, namely Ce, Gd, La, and Sc, have been reported to increase the growth of some microalgae and their content of lutein, violaxanthin, β-carotene, and chlorophylls (Goecke et al 2017). Microalgae from the Arthrospira and Chlorella genera were also experimentally shown to bioconcentrate some REEs such as Ce or Nd (Sadovsky et al 2016;Kücüker et al 2017). In the present study, all studied microalgal food supplements, except for one product based on Spirulina (exceeding maximum allowance limit) and one based on Chlorella (reaching 78% of the limit), were characterized by a relatively low content of REEs.…”

Silica-Coated Magnetic Nanocomposites for Pb2+ Removal from Aqueous Solution

“…Moreover, q L = 17.1 mg g −1 , is much closer to the experimental value, i.e., q m , exp = 14.9 mg g −1 . According to the literature, the fact that the adsorption process is better modelled according to the Langmuir model shows that the adsorption process is positively influenced by the increase in the concentration of metal ions [14] and that the adsorption process of Pb 2+ ions on the adsorbent occurs only in a monolayer, all surface sites are energetically identical housing a single Pb 2+ ion, and the ability of a Pb 2+ ion to adsorb on the surface is independent of occupying adjacent sites [43]. At the same time, the adsorption mechanism is controlled by chemosorption processes as a result of strong chelation between Pb 2+ ions and OHgroups and/or free electron pairs present on the surface of the adsorbent material [44].…”

Adsorption of rare earth elements using bio-based sorbents

“…However, there are several studies investigating marine brown algae [8] and marine biomass (seaweed and shell) [9] for the biosorption of REEs. According to the literature, biomass from green algae has been used as an effective biosorbent for the recovery of precious metals [10,11,12] as well as of neodymium obtained from hard disk drive magnets [13]. Chitosan is considered to be effective for uptake of metals as amino groups of chitosan chains work as coordination spots.…”