FTIR spectroscopy and scanning electron microscopic analysis of pretreated biosorbent to observe the effect on Cr (VI) remediation

Treatment of the Allura Red food colorant contaminated water by a novel cyanobacterium Desertifilum tharense

The biosorption properties of a newly isolated and identified cyanobacterium called Desertifilum tharense were investigated in the current study. Following morphological and molecular identification (16S rRNA sequencing analysis), the food colorant removal potential of this new isolate was determined. Moreover, the isotherm, kinetic, and thermodynamic studies were performed, and also the biosorbent characterization was studied after and before colorant biosorption with Fourier transform infrared and scanning electron microscopy analysis. Additionally, the changes in chlorophyll content of the biosorbent were examined after and before colorant treatment. The newly isolated cyanobacterial biosorbent removed 97% of Allura Red food colorant/dye at 1,500 mg L^-1 initial dye concentration successfully at optimal conditions. Langmuir isotherm and pseudo-second-order kinetic models were fitted with the biosorption of the dye. The D-R model showed that the biosorption process occurred physically. The chlorophyll-a content of the biosorbent was negatively affected by the biosorption. The newly isolated and identified cyanobacterium seems to be a successful candidate for use to treat highly dye concentrated wastewaters.

Bioremediation of Chromium by Microorganisms and Its Mechanisms Related to Functional Groups

Heavy metals generated mainly through many anthropogenic processes, and some natural processes have been a great environmental challenge and continued to be the concern of many researchers and environmental scientists. This is mainly due to their highest toxicity even at a minimum concentration as they are nonbiodegradable and can persist in the aquatic and terrestrial environments for long periods. Chromium ions, especially hexavalent ions (Cr(VI)) generated through the different industrial process such as tanneries, metallurgical, petroleum, refractory, oil well drilling, electroplating, mining, textile, pulp and paper industries, are among toxic heavy metal ions, which pose toxic effects to human, plants, microorganisms, and aquatic lives. This review work is aimed at biosorption of hexavalent chromium (Cr(VI)) through microbial biomass, mainly bacteria, fungi, and microalgae, factors influencing the biosorption of chromium by microorganisms and the mechanism involved in the remediation process and the functional groups participated in the uptake of toxic Cr(VI) from contaminated environments by biosorbents. The biosorption process is relatively more advantageous over conventional remediation technique as it is rapid, economical, requires minimal preparatory steps, efficient, needs no toxic chemicals, and allows regeneration of biosorbent at the end of the process. Also, the presence of multiple functional groups in microbial cell surfaces and more active binding sites allow easy uptake and binding of a greater number of toxic heavy metal ions from polluted samples. This could be useful in creating new insights into the development and advancement of future technologies for future research on the bioremediation of toxic heavy metals at the industrial scale.

A comprehensive analysis of biosorption of metal ions by macroalgae using ICP-OES, SEM-EDX and FTIR techniques

In the present study, a comprehensive approach to the biosorption process was proposed. Biosorption of Cr(III), Mn(II) and Mg(II) ions by a freshwater macroalga Cladophora glomerata was examined using several advanced techniques including FTIR (Fourier Transform Infrared Spectroscopy), ICP-OES (Inductively Coupled Plasma-Optical Emission Spectrometry) and SEM-EDX (Scanning Electron Microscopy with Energy Dispersive X-Ray Spectroscopy). The enriched biomass can become a valuable, bioactive feed additive for different breeds of animals. Additionally, the collected algal biomass was soaked in water in order to reduce the content of carbohydrate, what is especially important for animals with metabolic disorders. The content of starch was reduced by 22% but additionally some elements-mainly Si, K and P were removed from the biomass. It was shown that the natural macroalga had better biosorption properties than soaked. Cr(III) ions were sorbed by the biomass in the highest extent, then Mn(II) and finally Mg(II) ions. The content of chromium in the enriched algal biomass increased almost ~200 000 times, manganese ~75 times and magnesium ~4.5 times (both for Mg(II) ions used from magnesium sulphate, as well as from magnesium chloride) when compared to the natural Cladophora glomerata. In the case of the soaked biomass the increase of the content of elements in the enriched biomass was as follows ~17 165 times for Cr, ~25 times for Mn and for Mg ~3.5 times for chloride and 3.8 times for sulphate. The type of magnesium salt (chloride or sulphate) had no significant effect on the algal sorption capacity. The proposed mechanism of the biosorption is ion exchange in which mainly potassium participated. The applied FTIR analysis enabled the identification of the functional groups that participated in the biosorption process-mainly carboxyl and hydroxyl. The main changes in the appearance of the spectra were observed for the following wavenumbers- 3300-3400; 2900; 1700; 1400-1500 and 1200-1300 cm-1. The application of SEM-EDX proved that the metal ions were sorbed on the surface of both tested algae.

Use of Vegetable Fibers for PRB to Remove Heavy Metals from Contaminated Aquifers-Comparisons among Cabuya Fibers, Broom Fibers and ZVI

The Zero Valent Iron (ZVI) is the material most commonly used for permeable reactive barriers (PRB). For technical and economic reasons, hoter reactive substances usable in alternative to ZVI are investigated. The present study takes into account a vegetable fibers, the cabuya, investigating its capacity to retain heavy metals. The capacity of the cabuya fibers to adsorb heavy metals was verified in laboratory, by batch and column tests. The batch tests were carried out with cabuya and ZVI, using copper (Cu), zinc (Zn), cadmium (Cd) and lead (Pb). The results obtained by the cabuya fibers showed a very high adsorption capacity of heavy metals and resulted very similar to those obtained for the broom fibers in a previous study. The high value of the absorption capacity of the cabuya fibers was also confirmed by the analogous comparison made with the results of the batch tests carried out with ZVI. Column tests, using copper, zinc and cadmium, allowed to determine for the cabuya fibers the maximum removal percentage of the heavy metals considered, the corresponding times and the time ranges of the release phase. For each metal considered, for a given length and three different times, the constant of degradation of cabuya fibers was determined, obtaining values very close to those reported for broom fibers. The scalar behavior of heavy metal removal percentage was verified. An electron microscope analysis allowed to compare, by SEM images, the characteristics of the cabuya and broom fibers. Finally, to investigate the chemical structure of cabuya and broom fibers, the FTIR technique was used, obtaining their respective infrared spectra.