Chitosan functionalized with pyrazolinone derivative for water treatment: Application to Hg(II) removal

Due to its high toxicity, the removal of mercury from groundwater in contaminated industrial areas is of critical importance to avoid health problems for living beings. The functionalization of chitosan with pyrazolinone derivative, allows designing a sorbent (CH-PYZ) with high efficiency and selectivity for mercury sorption at acidic pH values (1.40 mmol Hg g-1, at pH 3). The sorbent is characterized by elemental analysis, thermogravimetric and textural analyses (increase in specific surface area and decrease in pore size), Fourier transform infrared spectroscopy, and shift of the pH point of zero charge toward higher value. The sorption was mainly performed through carbonyl, thiocarbonyl, hydroxyl, and amine groups. Under selected experimental conditions, sorption equilibrium is reached in 40 min (faster than crosslinked chitosan, CH) and the kinetic profile is fitted by the pseudo-first order rate equation. The Langmuir equation finely fits sorption isotherms: the functionalization improves both the maximum sorption capacity and the affinity coefficient (by four to six folds). The benefit of the functionalization is also demonstrated by the improved stability of the sorbent at recycling (loss at the fifth cycle does not exceed 2 % for CH-PYZ, against 8 % for CH). The grafting of pyrazolinone derivative brings another advantage in terms of selectivity against other mono-, di- and tri- valent metal ions. The sorbent also preferentially sorbs mercury from groundwater collected in a contaminated area. Under selected experimental conditions, the sorbent allows decontaminating the collected sample for livestock feeding, but the treated water cannot reach the levels for human drinking water.

Automated summary

The functionalization of chitosan with pyrazolinone derivative allows designing a sorbent with high efficiency and selectivity for mercury sorption. The sorbent demonstrates improved stability and selectivity compared to crosslinked chitosan. It can selectively adsorb mercury ions from contaminated groundwater and reaches sorption equilibrium in 40 minutes under acidic conditions.