Magnetic composite mineral sorbents based on saponite, spondyle, palygorskite clays and magnetite were created. The ability of magnetic
sorbents to remove tripolyphosphate and hexametaphosphate from aqueous solutions has been studied for different adsorbate concentrations
by varying the amount of adsorbent, temperature and shaking time. The kinetics of adsorption process data was examined using the pseudofirst-order, pseudo-second-order kinetics and the Boyd-Adamson internal diffusion kinetic models. The adsorption kinetics is best described
by the pseudo second-order model with good correlation (R
2 ≈ 1.00). The experimental isotherm data were analyzed using the Langmuir,
Freundlich, Temkin and Dubinin–Radushkevich equations. The experimental data well fitted to Langmuir isotherm model. It was found that
calculated adsorption capacities of magnetic composites relatively tripolyphosphate (550-620 mg g
-1
) and hexametaphosphate (670-730 mg
g
-1
) were good agreed with experimentally obtained values. The thermodynamic parameters, such as ΔG0
, ΔH0
and ΔS0 were also determined.
It was indicated that the adsorption of polyphosphates was feasible, spontaneous and exothermic in nature and the physical nature of the
process was confirmed. Thus, cheap magnetic sorbents based on natural clays and magnetite, which not only quickly separated from the
solution by magnetic separation, but effectively removed polyphosphates were obtained.
Key words: Composite magnetic sorbent, natural clay, magnetite, adsorption, magnetic separation
|
