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. 2021 Jul 10;26(14):4199.
doi: 10.3390/molecules26144199.

Biosorbents from Plant Fibers of Hemp and Flax for Metal Removal: Comparison of Their Biosorption Properties

Chiara Mongioví  1 , Nadia Morin-Crini  1 , Dario Lacalamita  1 , Corina Bradu  2 , Marina Raschetti  3 , Vincent Placet  3 , Ana Rita Lado Ribeiro  4 , Aleksandra Ivanovska  5 , Mirjana Kostić  6 , Grégorio Crini  1
Affiliations

Biosorbents from Plant Fibers of Hemp and Flax for Metal Removal: Comparison of Their Biosorption Properties

Chiara Mongioví et al. Molecules. .

Abstract

Lignocellulosic fibers extracted from plants are considered an interesting raw material for environmentally friendly products with multiple applications. This work investigated the feasibility of using hemp- and flax-based materials in the form of felts as biosorbents for the removal of metals present in aqueous solutions. Biosorption of Al, Cd, Co, Cu, Mn, Ni and Zn from a single solution by the two lignocellulosic-based felts was examined using a batch mode. The parameters studied were initial metal concentration, adsorbent dosage, contact time, and pH. In controlled conditions, the results showed that: (i) the flax-based felt had higher biosorption capacities with respect to the metals studied than the hemp-based felt; (ii) the highest removal efficiency was always obtained for Cu ions, and the following order of Cu > Cd > Zn > Ni > Co > Al > Mn was found for both examined biosorbents; (iii) the process was rapid and 10 min were sufficient to attain the equilibrium; (iv) the efficiency improved with the increase of the adsorbent dosage; and (v) the biosorption capacities were independent of pH between 4 and 6. Based on the obtained results, it can be considered that plant-based felts are new, efficient materials for metal removal.

Keywords: biosorption; felt; flax; hemp; lignocellulosic fiber; metals.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Hemp- and flax-based felts (below: optical microscopy images of the felt surface).
Figure 2
Figure 2
Comparison between removal (in %) of the seven metals by hemp and flax felts from single solutions using an initial metal concentration of 25 mg/L (other conditions: 1 g of felt in 100 mL of solution; contact time, 60 min; agitation speed, 250 rpm; temperature, 22 ± 1 °C; n = 5).
Figure 3
Figure 3
Effect of initial concentration (in mg/L) of seven metals (expressed in %) on their removal by (a) hemp- and (b) flax-based felts (other conditions: 1 g of felt in 100 mL of solution; contact time, 60 min; agitation speed, 250 rpm; temperature, 22 ± 1 °C; n = 3).
Figure 4
Figure 4
Comparison of the metal removal (in %) by different doses of (a) hemp- and (b) flax-based felts in 100 mL of mono-contaminated solutions with an initial metal concentration of 25 mg/L (other conditions: contact time, 60 min; agitation speed, 250 rpm; temperature, 22 ± 1 °C; n = 3).
Figure 5
Figure 5
Kinetics of metal removal (in %) by (a) hemp- and (b) flax-based felts at an initial concentration of 25 mg/L (other conditions: 1 g of felt in 100 mL of solution; agitation speed, 250 rpm; temperature, 22 ± 1 °C; n = 3).
Figure 6
Figure 6
Influence of pH on the removal (in %) of seven metals by (a) hemp- and (b) flax-based felts from mono-contaminated solutions at an initial concentration of 25 mg/L (other conditions: 1 g of felt in 100 mL of solution; contact time, 60 min; agitation speed, 250 rpm; temperature, 22 ± 1 °C; n = 3).
Figure 7
Figure 7
Comparison of Langmuir (a,b) and Freundlich (c,d) isotherms for 7 metals’ (Mn, Al, Co, Ni, Zn, Cd, Cu) adsorption onto hemp- and flax-based felts.
Figure 8
Figure 8
Comparison of metal removal (in %) from a solution containing a mixture of seven metals at two concentrations by (a) hemp- and (b) flax-based felts (other conditions: 1 g of felt in 100 mL of solution; initial concentration of each metal in solution, 25 or 50 mg/L; contact time, 60 min; agitation speed, 250 rpm; temperature, 22 ± 1 °C; n = 3).
Figure 9
Figure 9
Elemental analysis using energy-dispersive X-ray spectroscopy and scanning electron microscopy images of hemp- and flax-based felts before (a,c) and after (b,d) adsorption of a solution containing a mixture of seven metals.
See this image and copyright information in PMC

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