Spectrophotometric determination of some functional groups on Chlorella for the evaluation of their contribution to metal uptake

Potential of live Spirogyra sp. in the bioaccumulation of copper and nickel ions: A study on suitability and sustainability

AIM

Various industrial and municipal wastes are the major sources of heavy metal contamination in water causing significant environmental issues. Bioremediation is an effective and affordable solution for the removal of metals and metal pollutants from industrial wastewater. This study aimed to assess the efficacy of live and dead Spirogyra sp. for sorption of metals like of Cu²⁺ and Ni²⁺ .

METHODS AND RESULTS

The live Spirogyra sp. was used for the uptake of Cu²⁺ and Ni²⁺ from their aqueous solutions. The equilibrium data were fitted using a Langmuir and Freundlich isotherm model; the maximum uptakes for Cu²⁺ and Ni²⁺ were 29 and 521 mg g^-1 , respectively. Scanning electron microscopic (SEM) and infrared (IR) spectroscopic studies of Spirogyra sp. and treated Spirogyra sp. with specific metal ions were used to assess the bonding site and extent of sorption mechanism.

CONCLUSION

The initial study showed that this biomass takes up a significant amount of metal ions. Compared to the Langmuir model, the Freundlich model showed better sorption process. The pseudo-second-order rate model represented an enhanced kinetics of metal ion adsorption using live Spirogyra sp.

SIGNIFICANCE AND IMPACT OF THE STUDY

As bioaccumulation technology is environmental friendly and potentially cost-effective, live Spirogyra sp. is expected to be a good candidate for managing industrial wastewater.

Surface functional groups of carbon-based adsorbents and their roles in the removal of heavy metals from aqueous solutions: A critical review

Carbon-based adsorbents such as graphene and its derivatives, carbon nanotubes, activated carbon, and biochar are often used to remove heavy metals from aqueous solutions. One of the important aspects of effective carbon adsorbents for heavy metals is their tunable surface functional groups. To promote the applications of functionalized carbon adsorbents in heavy metal removal, a systematic documentation of their syntheses and interactions with metals in aqueous solution is crucial. This work provides a comprehensive review of recent research on various carbon adsorbents in terms of their surface functional groups and the associated removal behaviors and performances to heavy metals in aqueous solutions. The governing removal mechanisms of carbon adsorbents to aqueous heavy metals are first outlined with a special focus on the roles of surface functional groups. It then summarizes and categorizes various synthesis methods that are commonly used to introduce heteroatoms, primarily oxygen, nitrogen, and sulfur, onto carbon surfaces for enhanced surface functionalities and sorptive properties to heavy metals in aqueous solutions. After that, the effects of various functional groups on adsorption behaviors of heavy metals onto the functionalized carbon adsorbents are elucidated. A perspective of future work on functional carbon adsorbents for heavy metal removal as well as other potential applications is also presented at the end.

Removal and recovery of lead (Pb2+) from industrial effluent using indigenous and tailor-made Aureobasidium sp. RBSS-303

The objective of this study was to assess the removal and recovery of Pb-II from industrial wastewater using a locally isolated strain of Aureobasidium sp. RBSS-303. The initial Pb2+ concentration of 600 mg/L resulted in maximum uptake capacity (Qmax 235.1±0.3 mg/g). The biosorbent revival was attained by contacting with HCl (0.01 M), with 75.3% recovery of Pb2+. The Freundlich isotherm best explains the Pb2+ sorption performances. Maximum adsorption distribution coefficient of 1,309.6 mg metal/mL was observed at initial Pb2+ concentration value of 100 mg/L. Evaluation of nine kinetic models showed the removal rate of Pb2+ was reliant on diffusion control pseudo-second-order and saturation-mixed-order kinetic models with a high correlation coefficient value (R=0.99). Fourier transform infrared spectroscopy analysis showed the major contribution of -NH2 and -CN ligands of Aureobasidium sp. RBSS-303 in the sorption phenomenon of Pb2+. The biosorption assays carried out with effluent of the paint industry showed 76.8% efficiency for Pb2+ removal by the candidate biosorbent, regardless of the complex composition of the industrial effluent.

Physico-chemical study for zinc removal and recovery onto native/chemically modified Aspergillus flavus NA9 from industrial effluent

Zinc biosorption characteristic of locally isolated Aspergillus flavus NA9 were examined as a function of pH, temperature, pulp density, contact time and initial metal ion concentration. The maximum zinc uptake was found to be 287.8 ± 11.1 mg g(-1) with initial metal concentration 600 mg L(-1) at initial pH 5.0 and temperature 30 °C. The equilibrium data gave good fits to Freundlich and Florry models with correlation coefficient value of 0.98. The contribution of the functional groups and lipids to zinc biosorption as identified by chemical pretreatment was in the order: carboxylic acids > hydroxyl > amines > lipids. The mechanism of biosorption was also studied using Fourier transform infrared (FTIR) spectrometry, scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). The biosorbent was regenerated using 0.01 M HCl with 83.3% elution efficiency and was reused for five sorption-desorption cycles with 23.5% loss in biosorption capacity. The order of co-cations showing increased inhibitions of zinc uptake by A. flavus NA9 was Pb > Cu > Mn > Ni. The biosorption assays conducted with actual paint industry effluents revealed efficiency of 88.7% for Zn (II) removal by candidate biomass.

Simultaneous first order derivative spectrophotometric determination of vanadium and zirconium in alloy steels and minerals

A simple, selective and sensitive spectrophotometric method has been developed for the individual and simultaneous determination of trace amounts of vanadium(V) and zirconium(IV) in acetic acid medium using a newly synthesised reagent diacetylmonoxime salicyloylhydrazone (DMSH), without any prior separation. The molar absorptivity and Sandell's sensitivity of the coloured species are 1.30 x 10(4) and 1.82 x 10(4) L mol(-1)cm(-1) and 3.9 and 2.5 ng cm(-2) for V(V) and Zr(IV), respectively. Beer's law is obeyed between 0.26-2.80 and 0.30-3.20 μg mL(-1) concentration of vanadium (V) and zirconium (IV) at 405 and 380 nm respectively. The stoichiometry of the complex was found to be 1:1 (metal:ligand) for V(V) and 1:2 for Zr(IV) complexes. These metal ions interfere with the determination of each other in zero order spectrophotometry. The first derivative spectra of these complexes permitted a simultaneous determination of V(V) and Zr(IV) at zero crossing wavelengths of 445 nm and 405 nm, respectively. The optimum conditions for maximum colour development and other analytical parameters were evaluated. The proposed method has been successfully applied for the determination of zirconium and vanadium in standard alloy steel samples, mineral and soil samples.

Effect of humic acid on Cd(II), Cu(II), and Pb(II) uptake by freshwater algae: kinetic and cell wall speciation considerations

Thepresent study examines the effect of humic acid on the uptake kinetics of Cd(II), Cu(II), and Pb(II) by the freshwater alga Chlorella kesslerii. The results demonstrated that the relative proportion of Pb in the cell wall layer is greater than that of the internalized Pb, while internalized Cd and Cu were comparable or greater than the adsorbed metal concentration. In the presence of 10 mg L(-1) humic acid (HA), Cd and Cu uptake kinetics were consistent with that predicted by measured free metal concentrations. For Pb, the uptake flux and amount of lead bound to internalization and adsorption sites were an order of magnitude higher than those found at the same free lead ion concentrations in the presence of citric acid. Chemodynamic modeling suggested that the enhancement of the Pb uptake flux in the presence of HA originates from an increasing amount of Pb bound to the internalization sites through a ternary complex formation between lead-humic acid complex and internalization sites. Cell wall speciation calculations indicated that the lead-humic acid complex is the predominant species in the cell wall layer, while for Cu(II) and Cd(II) metal bound to the internalization (Cu) and adsorption (Cd) sites significantly dominated over the M-HA complex. The findings of the work show the relevance of the cell wall layer concentration and speciation and its key role in defining the local equilibrium conditions between metal and internalizations sites. The results of the present kinetic study have important consequences for improvement of the mechanistic understanding of the role of dissolved organic matter in metal uptake in phytoplankton and biogeochemical cycling of metals in the surface waters.

Bioremediation potential of Chlorella: spectroscopic, kinetics, and SEM studies

A dead dried alga, Chlorella sp., was used for the uptake of Cr+3, Cr2O7(-2), Cu+2, and Ni+2 from the aqueous solutions of these metal ions. The equilibrium data were fitted using the Langmuir and Freundlich isotherm model and the maximum uptakes for Cr+3, Cr2O7(-2), Ni+2, and Cu+2 were 98, 104, 108, and 183 mg/g, respectively. The Freundlich model, in comparison to the Langmuir model, better represented the sorption process. The kinetics of metal ions uptake by Chlorella sp. was best described by a pseudo-second order rate equation. Infrared spectroscopic data were employed to identify the site(s) of bonding in Chlorella sp. A scanning electron microscopic (SEM) study of pure dead Chlorella sp. and the species treated with different metal ions provided an idea of the extent of metal uptake by this species. The dead Chlorella sp took up maximum Cu(II). The size of the cell of the metal-treated Chlorella sp. obtained from SEM data is in agreement with the extent of metal uptake.

Spectroscopic and Scanning Electron Microscopy Studies of Bioaccumulation of Pollutants by Algae

The ability of Chlorella species and two other algal blooms collected locally to take up Cu(+2) and Ni(+2) was investigated using infrared and scanning electron microscopy (SEM) data. The percentage of metal uptake was determined with atomic absorption spectroscopy. The effects of pH and initial concentrations of metal ions on bioaccumulation were examined. The uptake of methyl orange dye by Chlorella species was also studied using Langmuir and Freundlich adsorption isotherms.