Publications in May & June 2014

In the mid-year, 227 articles have been released about chitosan. The main topics addressed nanoparticles, pharmaceutical preparations, evaluation studies, animals and humans. The leading nations in publishing chitosan-related articles are again China (69 articles), USA (28) and India (21). German scientists published 5 reports.

Table: Scientific journals, which released the largest number of publications, addressing chitosan in May and June 2014.
Source: GoPubMed

Water pollution by heavy metal ions like lead, mercury, cadmium or chrome represents an increasing issue for the environment today. Biosorption is a highly effective method to remove and recover heavy metals from aqueous solutions. Various chitosan-based biosorbents have been developed so far. Two promising articles and one summarizing review about chitosan-biosorbents are presented below.

Mercury removal from aqueous solutions with chitosan-coated magnetite nanoparticles optimized using the box-behnken design.

Rahbar N., Jahangiri A., Boumi S.et al.; Jundishapur journal of natural pharmaceutical products. Vol. 9 (2):e15913. eCollection. May 2014.

The objective of this study was to develop a non-toxic adsorbent, suitable to eliminate mercury ions from water solutions. Nanoparticles were made of magnetite (Fe3O4) and were coated with chitosan (CCMN). Parameters, affecting the adsorption efficiency, were calculated in advanced by using the “response surface methodology” (RSM). The adsorption rate is significantly determined by the initial metal concentration, pH of the solution and by the amount of adsorbent damped to the nanoparticle surface.

Conclusion:

• Adsorption rate: 99.91 % of Hg2+ (< 5 min); under certain conditions:
  • aqueous solution: pH = 5
  • Hg2+ concentration in the solution 6.2 mg/L
  • 0.67 g chitosan damped to the nanoparticle surface
• CCMN-particles have magnificent adsorption properties for low / moderate [Hg2+]
• Fast adsorption by electrostatic attraction or chemical binding between Hg2+ and functional groups of the CCMN surface

Source: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4036385/

Preparation of magnetic ionic liquid/chitosan/graphene oxide composite and application for water treatment.

Li L., Luo C., Li X. et al.; International Journal of Biological. Vol. 66:172-8. May 2014.

In this study a degradable biosorbent was developed to remove chrome (VI) from wastewater samples. Cr(VI) is an environmental hazard, since it is easily soluble in water, highly toxic and carcinogenic. The biosorbent was composed of magnetic chitosan and graphene oxide and was impregnated with ionic liquid (MCGO-IL). By using an external magnetic field the solid and liquid phases was rapidly separated. MCGO-IL could be used repeatedly and the production costs were low. Parameters like the pH of the solution, contact time and initial metal concentration affect adsorption efficiency directly and were analyzed in detail.

Results:

• MCGO-IL possess a large surface area and excellent magnetic properties
• Maximum adsorption capacity: 145.35 mg/g
• Cr(VI)-binding by strong intermolecular hydrogen bond with MCGO-IL
• Repeatedly usage of MCGO-IL
• IL-impregnation enhance Cr(VI)-adsorption

Source: http://www.sciencedirect.com/science/article/pii/S0141813014001159

Chitosan-based biosorbents: modification and application for biosorption of heavy metals and radionuclides.

Wang J., Chen C. Bioresource technology. Vol.160:129-41. June 2014.

This review summarizes the increasing knowledge of chitosan-based biosorbents very descriptively. The authors compare physically- and chemically-modified chitosan with regard to their metal sorption capacity, influence of pH-value of the solution, contact time and reusability.

The physical condition of a biosorbent (surface area, porosity, particle size) has great impact on the adsorbtion performance. Chitosan powders and flakes are non-porous and have a low surface area. As they tend to clog devices, they are not suitable for industrial applications. Gel beads are highly porous, have a large surface area and their resistance to acidic media can be enhanced by crosslinking. Gels represent the best metal sorbent form today. However, increasing efforts are being made to nanoparticle-based materials, as their specific surface area allows a selective removal of ions. The sorption capacity and chemical/mechanical resistance of a chitosan-based biosorbents are further determined by their concentration, degree of acetylation, crosslinking and viscosity.              

Overview:

Table: Chitosan and derivatives, which are used as heavy metal biosorbent. The complete list can be found in the publication. Source: http://www.sciencedirect.com/science/article/pii/S0960852413019500