Potential use of leaf biomass, Araucaria heterophylla for removal of Pb+2

Toxic heavy metal ions contamination in water and their sustainable reduction by eco-friendly methods: isotherms, thermodynamics and kinetics study

Heavy metal ions can be introduced into the water through several point and non-point sources including leather industry, coal mining, agriculture activity and domestic waste. Regrettably, these toxic heavy metals may pose a threat to both humans and animals, particularly when they infiltrate water and soil. Heavy metal poisoning can lead to many health complications, such as liver and renal dysfunction, dermatological difficulties, and potentially even malignancies. To mitigate the risk of heavy metal ion exposure to humans and animals, it is imperative to extract them from places that have been polluted. Several conventional methods such as ion exchange, reverse osmosis, ultrafiltration, membrane filtration and chemical precipitation have been used for the removal of heavy metal ions. However, these methods have high operation costs and generate secondary pollutants during water treatment. Biosorption is an alternative approach to eliminating heavy metals from water that involves employing eco-friendly and cost-effective biomass. This review is focused on the heavy metal ions contamination in the water, biosorption methods for heavy metal removal and mathematical modeling to explain the behaviour of heavy metal adsorption. This review can be helpful to the researchers to design wastewater treatment plants for sustainable wastewater treatment.

Heavy Metal Contamination in the Aquatic Ecosystem: Toxicity and Its Remediation Using Eco-Friendly Approaches

Urbanization and industrialization are responsible for environmental contamination in the air, water, and soil. These activities also generate large amounts of heavy metal ions in the environment, and these contaminants cause various types of health issues in humans and other animals. Hexavalent chromium, lead, and cadmium are toxic heavy metal ions that come into the environment through several industrial processes, such as tanning, electroplating, coal mining, agricultural activities, the steel industry, and chrome plating. Several physical and chemical methods are generally used for the heavy metal decontamination of wastewater. These methods have some disadvantages, including the generation of secondary toxic sludge and high operational costs. Hence, there is a need to develop a cost-effective and eco-friendly method for the removal of heavy metal ions from polluted areas. Biological methods are generally considered eco-friendly and cost-effective. This review focuses on heavy metal contamination, its toxicity, and eco-friendly approaches for the removal of heavy metals from contaminated sites.

Preferential adsorption of uranium by functional groups of the marine unicellular cyanobacterium Synechococcus elongatus BDU130911

This study reports the surface interaction of the chemically modified marine unicellular cyanobacterium Synechococcus elongatus BDU130911 with uranium. The selective functional groups of the control (dead biomass) for binding with uranium in unicellular marine cyanobacteria were identified as carboxyl groups. The adsorption capacity of the biomass in a 1 mM uranium solution was found to be 92% in the control, 85% in the amine-blocked treatments, and 20% in the carboxyl-blocked treatments. The Langmuir isotherm provided a good fit to the data, suggesting a monolayer of uranium adsorption on all the tested biomass. The functional groups involved in the adsorption of uranium by the control and modified biomass were assessed by Fourier transform infrared spectroscopy, energy dispersive X-ray fluorescence and X-ray diffractive analysis. The results of this study identify, carboxyl groups as the dominant anionic functional group involved in uranium adsorption, which validates an ionic interaction between the biomass and uranium, a cationic metal.

Design of hybrid PVA-CA-Jania rubens biomatrix for removal of lead

Polyvinyl alcohol-sodium alginate (PVA-SA) matrix was fabricated and red algae Jania rubens was embedded for removal of lead from aqueous solutions. The Pb(II) uptake rate was rapid primarily at 1 h and equilibrium was achieved within 2 h. The optimum pH was 5, the data were well fitted by Langmuir and Freundlich models, and R_L values are in the range of 0.1-0.38. The sorption capacity (q_e) of PVA-calcium alginate (CA)-J. rubens matrix increased from 10.77 to 37.195 mg g^-1 with increasing Pb(II) concentration from 24.86 to 98.75 mg L^-1 at the temperature of 30°C and pH 5. The sorption capacity (q_e) and maximum biosorption (q_m) were noted as 37.179 ± 0.32 and 71.43 mg/g, respectively. The adsorption process was well described by pseudo-second-order model. The reaction is endothermic, is spontaneous, and increases in randomness. The functional groups present on matrix, i.e., -OH, -C-N, -C-O,-CO-NH, -NH₂, -SH, and -C-OH, were intensely involved in the process. Scanning electron microscopy results revealed the morphological changes due to adsorption of Pb(II) on and inside of PVA-CA-J. rubens matrix. Desorption study indicates the efficient regeneration of PVA-CA-J. rubens biomass matrix for three cycles and is a promising matrix for removal of Pb(II) and can be used in continuous systems.