RESUMO
A novel cost-effective and multifunctional nanocomposite was developed based on sustainable macroalgae biomass. The brown seaweed Sargassum latifolium was utilized for alginate extraction and the calcareous red seaweed Tricleocarpa fragilis was utilized as CaCO3 source for nanohydroxyapatite synthesis. The developed Zn2+-crosslinked alginate/nanohydroxyapatite (ZA/nHA) beads were characterized by FT-IR, XRD, and TEM. The antimicrobial potential of ZA/nHA to disinfect synthetic Escherichia coli-contaminated water was evaluated at different bacterial load and composite concentrations. The developed ZA/nHA effectively inactivated bacteria at initial concentration ≤ 105 CFU mL-1 and 0.5-1% (w/v) of ZA/nHA within 300-360 min. The kinetics of bacterial disinfection exhibited better fitting to Weibull model than Log-liner model, which confirmed the disinfection process. Furthermore, treatment of the cyanobacterium (Chroococcus sp.) and the microalga (Chlorella sp.) with ZA/nHA showed promising antialgal properties as indicated by reductions in chlorophyll a. The treatment indicated 100% and 90% removal of Chroococcus sp. and Chlorella sp. within 2 and 4 days, respectively. The developed ZA/nHA also exhibited a promising application as a biosorbent for crystal violet (CV). The adsorption process was very fast (0.171 mg CV g-1 adsorbent was removed within 7 min at pH 6.0). The adsorption kinetics exhibited better fitting to the pseudo-second order and Elovich models than the pseudo-first order equation. Besides, Sips model better represented the isotherm data of CV adsorption. The thermodynamic analysis indicated exothermic adsorption, which became more favorable at low temperature and high CV concentration. The developed nanocomposite is eco-friendly and suitable for multiple environmental applications.
RESUMO
BACKGROUND: Despite being necessary, copper is a toxic heavy metal that, at high concentrations, harms the life system. The parameters that affect the bioreduction and biosorption of copper are highly copper-resistant bacteria. RESULTS: In this work, the ability of the bacterial biomass, isolated from black shale, Wadi Nakheil, Red Sea, Egypt, for Cu2+ attachment, was investigated. Two Cu2+ resistance Bacillus species were isolated; Bacillus pumilus OQ931870 and Bacillus subtilis OQ931871. The most tolerant bacterial isolate to Cu2+ was B. pumilus. Different factors on Cu2+ biosorption were analyzed to estimate the maximum conditions for Cu biosorption. The qmax for Cu2+ by B. pumilus and B. subtilis determined from the Langmuir adsorption isotherm was 11.876 and 19.88 mg. g-1, respectively. According to r2, the biosorption equilibrium isotherms close-fitting with Langmuir and Freundlich model isotherm. Temkin isotherm fitted better to the equilibrium data of B. pumilus and B. subtilis adsorption. Additionally, the Dubinin-Radushkevich (D-R) isotherm suggested that adsorption mechanism of Cu2+ is predominately physisorption. CONCLUSION: Therefore, the present work indicated that the biomass of two bacterial strains is an effective adsorbent for Cu2+ removal from aqueous solutions.