Environmental friendly iron oxide based magnetic nanomaterials : Synthesis, characterization and application for arsenic removal

Abstract

The present study focuses on the application of iron oxide nanomaterial for the abetment
of arsenic from contaminated water with a view to provide clean drinking water to the
society. The current research signifies the use of iron oxide nanoparticles and composite of
iron oxide nanoparticles with some supporting biomaterials are used as adsorbent for the
removal of arsenic from water.
Attempts have been made to synthesize Fe3O4 nanoparticles, JF@Fe2O3 nanocomposite
(Jute Fiber), AMP@Fe2O3 nanocomposite (Aegle Marmelos powder) and Fe3O4/CSAC
nanocomposite (cigarette soot activated carbon) by microemulsion, hydrothermal and
thermal pyrolysis process. For confirmation of materials formation, these are characterized
by instrumental techniques like XRD, SEM, FESEM, TEM, EDX, FTIR, BET, VSM,
and Zeta potential study. The concentration of arsenic is determined by AAS analytical
technique following the standard procedure after magnetic separation of adsorbent from
solution. All the synthesized adsorbents are used for the removal of arsenic in both the
oxidation states of As(III) and As(V) from synthetic aqueous solution through batch
adsorption process. The effect of common coexisting ions Cl- NO3-, SO42􀀀, SiO32−,CO32-, and PO43- are examined on the removal of arsenic by all these materials. These materials are regenerated with NaOH solutions after that they are exhausted and used up to
four consecutive cycles.
Fe3O4 nanoparticle is synthesized by water-in-oil microemulsion process by using a
novel bio-degradable anionic, non-ionic phosphate free surfactants called Extran and used
for As(III) removal. The Box-Behnken Design (BBD) of response surface methodology
(RSM) technique is applied to different variables parameters such as adsorbent dose, initial
As(III) concentration and solution pH to know the optimum condition for better removal of
As(III). From the study of the model, the optimum conditions are found to be: initial As(III)
concentration 33.32 mg/L, adsorbent dose 0.70 g/L, and solution pH 7.7. In this optimum
condition, about 90.5% of As(III) is removed from the aqueous solution. The maximum
adsorption capacity is found to be 7.18 mg/g at room temperature as calculated from the
Langmuir isotherm model.
An environmental friendly material of JF@Fe2O3 nanocomposite (Jute Fiber) is synthesized and used for As(V) removal. In this material, the cellulose matrix of JF is
covered with Fe2O3 nanoparticles and form an efficient hybrid adsorbent. This composite
possesses a very small particle of Fe2O3 with an average size of 11 nm and having a
surface area (BET) of 95.43 m2/g. The removal rate of As(V) is maximum by JF@Fe2O3
nanocomposite at a solution pH 3 with maximum adsorption capacity of 48.06 mg/g as
calculated from the Langmuir isotherm plot. The R2 value (0.995) of adsorption process
confirms the pseudo-second-order kinetics model. The driving force for the adsorption
involves two types of interaction: (I) electrostatic attraction and (II) ligand exchange process.
A novel magnetic bio-adsorbent is derived from the leaves of Aegle Marmelos tree.
Here, AMP@Fe2O3 nanocomposite (Aegle Marmelos powder) is synthesized and applied
for As(V) removal from aqueous solution in batch mode. The rate of removal of As(V)
by the material is maximum at a solution pH 3 with an equilibrium time of 250 min.
The experimental data are best fitted to the pseudo-second-order kinetic based on the R2
value of 0.992. The composite has a good uptake capacity of 69.65 mg/g as found from
Langmuir isotherm model. The zeta potential and FTIR analysis before and after adsorption
demonstrates that two types of mechanism are occurred. First one is an electrostatic
attraction between negatively charged As(V) ions (H2AsO4-) and protonated −OH present
on the Fe2O3 surface and second is due to exchange of hydroxyl groups by As(V) ions.
A novel Fe3O4/CSAC nanocomposite (cigarette soot activated carbon) adsorbent is
synthesized from the waste of burned cigarette. On analysis, it is found that the material
possess a surface area of 575.604 m2/g, lower pore size of 6.8 nm, smaller particle size of
less than 10 nm and good magnetic properties (10.77 emu/g) for the removal of arsenic. The
arsenic removal by this material is controlled by solution pH with a removal percentage of
91% and 93% for As(III) and As(V) at pH 7 and 3, respectively. The Langmuir isotherm
model is best fitted model based on the R2 value with the uptake capacities of 80.99 and
107.96 mg/g for As(III) and As(V), respectively. The kinetic study of the adsorption process
confirms the pseudo-second-order kinetics with an equilibrium contact time of 90 min. The
results of this study indicate that the Fe3O4/CSAC material is a better adsorbent for arsenic
removal from the water system.