The potential of chitosan intercalated nickel/iron layered double hydroxide composites as extraction adsorbent for phthalates

Abstract

In this research, the potential utility of chitosan-nickel/iron LDHs (CS-Ni/Fe LDHs) has been examined for the separation and pre-concentration of five phthalates (PAEs: diethylphthalate (DEP), dipropylphthalate (DPP), dibutylphthalate (DBP), benzylbutylphthalate (BBP), and dioctylphthalate (DOP)). The extraction efficiency of CS-Ni/Fe LDH composites against the target phthalates is studied through the control of the key variables (e.g., eluent type, elution volume, flow rate, adsorbent amount, solution pH, and salt addition effect). Under the optimal conditions, the method detection limit towards target PAEs is estimated as 0.023–0.033 ng/mL over a 0.1–100 ng/mL range (R2>0.999). The CS-Ni/Fe LDH composites are utilized successfully to extract PAEs in real samples such as perfume, cream, bottled water, and bottled milk (recovery: 97.3–136.8%). The spent CS-Ni/Fe LDH composites can be regenerated at least over 30 cycles. The good agreement in adsorption isotherms with the non-linear Langmuir model indicates the formation of monolayered PAE molecules over CS-Ni/Fe LDH composites. The computed partition coefficients (mg g−1μM−1) for CS-Ni/Fe LDH are found as follows: DOP (802) > DBP (491) > DPP (355) > DEP (248) > BBP (247). The thermodynamic analysis reveals the exothermic and spontaneous behavior of the adsorption process. The CS-Ni/Fe LDHs are thus identified as efficient sorbent media for PAEs through hydrogen bonding and hydrophobic interactions. Accordingly, CS-Ni/Fe LDH composites are recommended as a useful option for capturing PAEs under real-world conditions.