Magnetic nanoparticle complex

1. A method for preparing a magnetic nanoparticle complex, comprising:

preparing a pre-ligand comprising:

at least one amino group; and

at least one carbamate group or dithiocarbamate group;

associating the pre-ligand with a magnetic nanoparticle; and

modifying the pre-ligand associated with the magnetic nanoparticle to form a ligand associated with the magnetic nanoparticle, the ligand comprising:

a functional group configured to combine with an acid component in an oil or a conjugate base of the acid component;

wherein:

the functional group comprises an amine group configured to combine with an acid component, or an ammonium group configured to combine with the conjugate base of the acid component;

a nitrogen atom of the ammonium group is bound with at least one hydrocarbon group;

the hydrocarbon group is a substituted or unsubstituted C 8 -C 20 alkyl, cycloalkyl, alkenyl, alkynyl, aryl, or aralkyl group; and

the ligand associated with the nanoparticle is a magnetic nanoparticle complex.

2. The method of claim 1 , further comprising treating the pre-ligand with a basic solution including a hydroxide ion after contacting at least one hydrocarbon group with at least one amino group.

3. The method of claim 1 , wherein:

the ligand comprises both of following structural units:

wherein:

R 1 is C(O)O − or C(S)S − ; and

R 2 and R 3 are each independently a hydrogen, alkyl, cycloalkyl, alkenyl, alkynyl, aryl, or aralkyl group, with the proviso that R 2 and R 3 are not hydrogen concurrently, and at least one of R 2 and R 3 is a C 8 -C 20 hydrocarbon group.

4. The method of claim 1 , wherein preparing the pre-ligand comprises contacting a compound of Formula I:

with CS 2 or CO 2 ;

wherein n is an integer from 0 to 50.

5. The method of claim 1 , wherein:

preparing the pre-ligand comprises contacting CS 2 or CO 2 with a compound of Formula I:

wherein at least some of hydrogen atoms in the secondary amino groups in the compound of Formula I are substituted by an aminoalkyl group, an aminocycloalkyl group, or an aminoaryl group; and n is an integer from 1 to 50.