A Promising Use of Trimethyl Chitosan for Removing Microcystis aeruginosa in Water Treatment Processes

Abstract

The increase in cyanobacterial blooms linked to climate change and the eutrophication of water bodies is a global concern. The harmful cyanobacterium Microcystis aeruginosa is one of the most common bloom-forming species whose removal from fresh water and, in particular, from that used for water treatment processes, remains a crucial goal. Different biodegradable and environmentally friendly coagulants/flocculants have been assayed, with chitosan showing a very good performance. However, chitosan in its original form is of limited applicability since it is only soluble in acid solution. The objective of this work was therefore to test the coagulant/flocculant capacity of trimethylchitosan (TMC), a chitosan derivative produced from residues of the fishing industry. TMC has a constitutively net positive charge enabling it to remain in solution regardless of the pH. Results show that even at alkaline pHs, common during cyanobacterial blooms, TMC is effective in removing buoyant cyanobacteria from the water column, both in test tube and Jar-Test experiments. Cell integrity was confirmed by fluorescent stain and electron microscopy. Our findings lead us to conclude that the use of TMC to remove bloom cells early in the treatment of drinking water is both feasible and promising.

Biosorption of Escherichia coli Using ZnO-Trimethyl Chitosan Nanocomposite Hydrogel Formed by the Green Synthesis Route

“…The presence of a band at 547 and 748 cm −1 in the spectra is a fingerprint of zinc-oxide vibration that underwent structural changes from the 471-614 cm −1 identified in the spectra of uncoated TM@ZnO NPs. Other authors also reported similar peaks indicating the surface coating of ZnO NPs with chitosan biopolymer [21,28,43,46]. The spectral profiles of TM@ZnO/TMC NC hydrogel on interaction with E. coli underwent some conformational changes in the broad peaks assigned to the stretching vibrations of the amines and -OH (3000-3129 cm −1 ).…”

“…Also, Aqueous Piper beetle leaf extract was reported by Thi Tran [41] to mediate the formation of a spherical shape ZnO NPs. A spherical/cubic and hexagonal shape for the ZnO NPs prepared from the extracts of Mentha pulegium were reported in a study to give a particle size distribution of 320 nm on the surface coating with chitosan [21]. Similarly, ZnO NC coated with chitosan (chitosan-ZnO) was observed to show a dendritic floc-like structure in a study reported by Bashal [28].…”

“…The crystallite size of ZnO NPs coated with chitosan derived from shells, crab shells, and Streptomyces griseus bacteria were observed to vary between 30.9 and 35.8 nm [27]. The crystallite size of ZnO/CS due to the surface coating with the biopolymer was observed to induce a reduction in the intensities of the peaks with crystallite size of 45 nm [21], similarly due to the broad stuff of chitosan at 22° in a study by Agnes [46] to possess the crystallite size of 21.45 nm and 16.57 nm for CS-ZnO and FA-CS-ZnO NPs, respectively. The zeta potential (ζ-potential) of biosynthesized TM@ZnO/TMC NC hydrogel investigated using the DLS technique was estimated at 23.5 ± 5.13 mV (Figure 3b).…”

“…Surface coating using biopolymer was reported to enhance the chemical and biological properties of metal oxide NPs. Pristine chitosan, though reported to be biodegradable, readily accessible naturally, possess low toxicity, and have chemical functionality as adsorbents, was further observed to demonstrate few drawbacks in its application as adsorbents due to its preferential solubility in acidic medium [21]. However, appropriate modification in the form of TMC-based particles was reported to demonstrate higher adsorption capacity, biocompatibility, and nontoxicity in biological milieu than pristine chitosan.…”