The present work investigated the ability of algal biomass Chlorella vulgaris to remove mercury from aqueous solutions. The mercury biosorption process was studied through batch experiments 35 C temperature with regard to the influence of contact time, initial mercury concentration, pH and desorption. The maximum adsorption capacity was registered at pH 6. The adsorption conduct of Hg(II) was defined by pseudo second order well rather pseudo first order as the experimental data (q e ) come to an agreement with the calculated value. The kinetics of adsorption was fast and a high capacity of adsorption occurred within only 90 min. The adsorption data were signified by many models but Langmuir (q max ¼ 42. mg g À1 ) & Freundlich fitted well having regression coefficients near to unity. The thermodynamic parameters were also suited well as negative value of free energy cope up to spontaneity, positive value of the randomness described by ΔS attributed to affinity of Hg þ2 towards algal bioadsorbant and high positive value of heat of enthalpy designates that the adsorption process is expected due to robust interactions between the Hg(II) ions and various functional groups on surface of algal bioadsorbant. Field emission scanning electron microscopy integrated with energy dispersive X-ray spectroscopy analysis before and after adsorption of Hg(II) reveals the adsorption of metallic ions over the surface. FTIR study supported the existence of various functional groups (carboxylix, amines, hydroxyls, amides etc.) helped in adsorption. Continuous adsorption desorption experiments proved that algal cells was excellent biosorbents with potential for further development.

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In this study, adsorption of three different heavy metals i.e. cadmium (Cd (II)), copper (Cu (II)) and nickel (Ni (II)) was carried out in single and multi-contaminated system using coal-fired fly ash (CFFA). Initially, for the single contaminated system, various physical process parameters were selected for optimization by deploying Box–Behnken design of experiments. Further, the evaluation of CFFA for removal of heavy metals in a multi-component system from aqueous solution was performed by employing Plackett-Burman design of experiments with all the three heavy metals at two different levels by varying their initial concentration (10–50 mg L−1). In both the aforementioned cases, CFFA showed its great potential for heavy metal removal, i.e. single and multi-component system and followed the order: Cu (II) > Ni (II) > Cd (II). Further, FTIR study confirmed the involvement of amide, aldehyde, alkoxy, alkanes, and alkene groups for heavy metal adsorption by CFFA.

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This review discusses the use, mode of action, biomarkers, and bioindicators of inorganic arsenic and mercuric fungicides, as well as their effects on the environment and human health. The most prevalent indicator of exposure to arsenic is the measurement of total arsenic in urine. Biomarkers of exposure for arsenic and inorganic fungicides incudes the analysis of hair, urine, blooda and nails. Bio indicators are species or group of species that are used to indicate adverse effect of contamination. Freshwater fish species act as a very good bio indicator for inorganic arsenic. Tree bark, rice fields and sea birds could be a valuable indicator of inorganic arsenic contamination. Black Piranha, fish and earthworms are an ideal bio indicator of inorganic mercury. Inorganic arsenic compounds are known to be highly carcinogenic and toxic compounds. Mercuric fungicide is very toxic when inhaled by humans or animals it causes severe health issues and when absorbed by plants it retards their growth.  To estimate the daily dose of arsenic exposure to humans through absorption, ingestion and other pathways, Average daily dose is implemented by using two equations from the US EPA. To determine the ecological risk assessment a simplified equation was proposed by FDA i.e. HQ = E/RfD. Overall, the review emphasizes the need for heightened awareness, regulation, and alternative approaches to fungicide use, with a focus on minimizing the use of inorganic arsenic and mercuric fungicides to safeguard the environment and promote sustainable agricultural practices.