Polycyclic Aromatic Hydrocarbon Sorption by Functionalized Humic Acids Immobilized in Micro- and Nano-Zeolites

Polycyclic aromatic hydrocarbons (PAHs) are hazardous compounds originating from anthropogenic activity. Due to their carcinogenic properties for humans, several technologies have been developed for PAH removal. Sorption with natural and organic materials is currently one of the most studied due to its low cost and its environmentally friendly nature. In this work, a hybrid sorbent involving functionalized humic acids (HAs) and nano-zeolite is proposed to entrap PAHs. The use of functionalized HAs immobilized in a porous support is designed to address the instability of HAs in solution, which has been already reported. HA functionalization was carried out to increase the non-polarity of HAs and aliphatic group formation. The HAs were functionalized by esterification/etherification with alkyl halides, and their chemical changes were verified by FTIR and NMR. The sorption isotherms of the functionalized HAs in micro- and nano-zeolites were used to assess the performance of the nano-zeolites in adsorbing these HAs. The hybrid support allowed the removal of anthracene and pyrene at percentages higher than 90%; fluoranthene, of angular molecular structure, was adsorbed at 85%. PAHs are ubiquitous in the environment, and a stable sorption of them in solid matrices will allow their removal from the environment through effective and environmentally friendly methods.

Swelling and kinetic investigations of basic blue-3 sorption by polyacrylamide/Gum Arabic hybrid hydrogel in aqueous medium

Removal of noxious dyes from waste water is highly desirable for the safety of humans, aquatic life and natural environment. The issue was addressed in the present work by one pot fabrication of polyacrylamide/Gum Arabic (pAAm/GA) composite hydrogel which was applied as sorbent for basic blue-3 (BB3) eradication. The synthesis of the material was confirmed by scanning electron microscopy (SEM), Fourier Transformed Infrared (FTIR) spectroscopy and thermo gravimetric analysis (TGA). Besides, the same techniques also evidenced BB3 uptake by the hydrogel. In distilled water, the swelling capacities of the hydrogel was investigated at pH 7 and the nature of water diffusion into the hydrogel was probed from the resultant data. The composite hydrogel reached equilibrium point in 24 h after which no appreciable water absorption occurred. The adsorption of BB3 by the hybrid material was comprehensively investigated which involved the effect of contact time, temperature and pH on the sorption capacity of the hybrid sorbent. The obtained data fitted well into pseudo second order kinetic model and the adsorption took place in three consecutive kinetic phases. Moreover, sorption thermodynamics revealed non spontaneous and endothermic nature of BB3 sorption accompanied with increase in degree of order.

Isolation of Efficient Metal-Binding Bacteria from Boreal Peat Soils and Development of Microbial Biosorbents for Improved Nickel Scavenging

Boreal peatlands with low iron availability are a potential, but rarely studied, source for the isolation of bacteria for applications in metal sorption. The present research focused on the isolation and identification of Actinobacteria from northern Finland, which can produce siderophores for metal capture. The 16S rDNA analysis showed that isolated strains belonged to Firmicutes (Bacillus sp.) and Actinobacteria (Microbacterium sp.). The culture most efficiently producing siderophores in the widest array of the media was identified as Microbacterium sp. The most appropriate media for siderophore production by the Microbacterium strain were those prepared with glucose supplemented with asparagine or glutamic acid, and those prepared with glycerol or fructose supplemented with glutamic acid. The microorganism obtained and its siderophores were used to develop Sphagnum moss-based hybrid biosorbents. It was showed that the hybrid sorbent could bind nickel ions and that the nickel removal was enhanced by the presence of siderophores. Bacterial cells did not have a significant effect on sorption efficiency compared to the use of siderophores alone. The microbial biosorbent could be applied in the final effluent treatment stage for wastewater with low metal concentrations.