Heavy-metal pollution is a persevering environmental menace, which demands the necessity of its removal by green and ecofriendly adsorbents. To combat this problem, discarded plant biomass can be used as an efficient substitute. Herein, a comparative study has been highlighted for the removal of Pb2+ ions using Euryale ferox Salisbury seed coat and its activated carbon, which is prepared by a first-time-reported activating agent that is a novel and non-hazardous bioresource. The batch investigation revealed a 99.9% removal efficiency of Pb(II) by the activated carbon compared to Euryale ferox Salisbury seed coat, which shows only an 89.5% removal efficiency at neutral pH. The adsorption mechanism is mainly a multilayered process, which involves electrostatic, van der Waals, and hydrogen bonding interactions. The adsorption equilibrium, kinetic, and thermodynamic studies were examined for the biosorbents, which revealed the adsorption process to be feasible, spontaneous, and exothermic with both physisorption and chemisorption adsorption mechanisms. The desorption study asserted the reusability of both the biosorbents to a maximum of three cycles.

Petroleum sludge is uncontrollably released in oil field and refineries which can lead to deleterious effect on the environment, as it consists of components of emerging concern such as PAHs, BTEX components, heavy metals, asphaltenes etc. In the present study, a novel bacterium Enterobacter cloacae AR-IASST (01), that have the potential to produce biosurfactant (surface tension reduced to 26.4 mN/m) was utilized to degrade petroleum sludge. A degradation of 86.9% was achieved after 5 days of culture incubation and biosurfactant production was also observed during the degradation process of sludge. In the GC-MS analysis, the peaks numbers reduce from 184 to 13 in the treated sample and complete degradation of PAHs present in the sludge was observed. The biosurfactant was characterized to be rhamnolipid in nature. The biosurfactant exhibited attractive emulsification towards several oils and an E24 of 100% was achieved against crude oil. The biosurfactant was found to be stable over a wide range of temperature, and salt concentration, although it showed sensitivity in high acidic condition. Furthermore, it was found that the bacterial treatment also led to the removal of heavy metals (Ni), zinc (Zn), lead (Pb), iron (Fe), chromium (Cr), copper (Cu), present in the sludge sample. Thus, the present study reveals that the novel bacterium is very potential and can be widely used for restoration of petroleum sludge contaminated sites in future.

Petroleum sludge is uncontrollably released in oil field and refineries which can lead to deleterious effect on the environment, as it consists of components of emerging concern such as PAHs, BTEX components, heavy metals, asphaltenes etc. In the present study, a novel bacterium Enterobacter cloacae AR-IASST (01), that have the potential to produce biosurfactant (surface tension reduced to 26.4 mN/m) was utilized to degrade petroleum sludge. A degradation of 86.9% was achieved after 5 days of culture incubation and biosurfactant production was also observed during the degradation process of sludge. In the GC-MS analysis, the peaks numbers reduce from 184 to 13 in the treated sample and complete degradation of PAHs present in the sludge was observed. The biosurfactant was characterized to be rhamnolipid in nature. The biosurfactant exhibited attractive emulsification towards several oils and an E24 of 100% was achieved against crude oil. The biosurfactant was found to be stable over a wide range of temperature, and salt concentration, although it showed sensitivity in high acidic condition. Furthermore, it was found that the bacterial treatment also led to the removal of heavy metals (Ni), zinc (Zn), lead (Pb), iron (Fe), chromium (Cr), copper (Cu), present in the sludge sample. Thus, the present study reveals that the novel bacterium is very potential and can be widely used for restoration of petroleum sludge contaminated sites in future.

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