Adhesive Stalks of DiatomDidymosphenia geminataas a Novel Biological Adsorbent for Hazardous Metals Removal

Abstract

The application of biomass derived from the nuisance fresh‐water diatom species Didymosphenia geminata toward the adsorption and removal of heavy‐metal ions from water is reported. The cell‐free polysaccharide‐based stalks of these diatoms are used as adsorbents to remove harmful metal ions: Pb(II), Ni(II), and Cd(II). Detailed analyses of the adsorption kinetics using both pseudo‐first‐order model and pseudo‐second‐order models are performed. The results show a strong correspondence to a pseudo‐second‐order kinetic model. The Langmuir and Freundlich models are used to describe the adsorption isotherms. The correlation coefficients (r2) of the Langmuir model are equal to 0.994 (Pb2+), 0.995 (Cd2+), and 0.995 (Ni2+), and the r2 for the Freundlich model are equal to 0.991 (Pb2+), 0.991 (Cd2+), and 0.987 (Ni2+). The experimental data for all metal ions strongly support the Langmuir isotherm model. It is shown that stalks of D. geminata exhibit exceptional sorption capacity (qm) for Pb(II) ions of 175.48 mg g−1. Additionally, a high sorption capacity for Cd(II) (145.86 mg g−1), and Ni(II) (130.27 mg g−1) is observed. The thermodynamic aspects of the adsorption process of selected metal ions are also discussed. Preliminary tests investigating applications of D. geminata stalks for sewage purification from galvanic industry and battery and accumulator production were performed. These comprehensive studies show that D. geminata can be robustly applied for the removal of harmful metal ions from wastewater.

Lignin/Chitin Films and Their Adsorption Characteristics for Heavy Metal Ions

“…To investigate the type of adsorption mechanism for Fe­(III) and Cu­(II) of the lignin/chitin films, two kinetic models (pseudo-first-order and pseudo-second-order) were evaluated. ,, …”

“…Numerous research work toward the development of various technologies for the removal of toxic metal ions from water have been reported such as ion exchange resins, chemical precipitation and coagulation-flocculation, , electrolytic reduction, membrane technology, and biosorbents . Many alternatives with respect to fossil resource based solid-phase sorbents prepared from the renewable resources such as cellulose, lignin, and chitin have gained special attention. − …”

“…Because of its chemical stability, high reactivity, and nontoxicity, chitin is considered to be an attractive biomaterial. , The common features of both lignin and chitin are their feasible accessibility, biocompatibility, and environmental beneficial properties. Furthermore, it was reported that both biopolymers showed a sorption affinity for heavy metal ions. − Hence, lignin and chitin composite materials could be applied as a replacement for products from fossil resources. − , …”

Didymo and Its Polysaccharide Stalks: Beneficial to the Environment or Not?

“…While most of the research surrounding D. geminata has focused on its structure, management, and possible negative impacts, there has been recent research published that demonstrates the possible positive effects that Didymo can have on the environment. In a paper written by Wysokowski et al [5], the authors state that the polysaccharide stalks of D. geminata have the ability to absorb harmful metal ions, such as Pb (II), Ni (II), and Cd (II). These stalks contain large amounts of complex extracellular biopolymers, which allows them to remove metals comparable to other polysaccharides.…”

“…However, if the benefits of Didymo appear to outweigh its Their structure is considered to be helpful when it comes to metal removal applications due to the large amounts of complex extracellular biopolymers. Due to this characteristic, they are being considered as a fibrous absorbent of lead (II), nickel (II), and cadmium (II) in wastewater systems [5]. As more research was done on this species of algae, it was found that Didymo would be transferred to different parts of the river by sticking to the bottom of fishermen's boots.…”