## Arsenic Removal by MIPs
### As(V) (Arsenate)
Furthermore, after 25 regenerated cycles using 0.5 M HCl as the extraction solvent, the loss of initial adsorption capacity was only 3.1%. Additionally, the membrane also showed good antibacterial properties that can be used to prevent biofouling of the membranes [80]. Moreover, an imprinted polymer with nanopores (nanoMIP) has been used to remove arsenic from water [81]. Fluorescein was preferred as the chelating agent for As(V), combined with rhodamine B, dithizone, and EDTA. The formed fluorescein-As(V) complex reacted with the functional monomer, 4-vinyl pyridine (4-VP), followed by the addition of a cross-linking monomer, ethylene glycol di-methacrylate (EGDMA) in methanol. The polymer particles were fractionated using technical sieves. The adsorption capacity of nanoMIP for As(V) was 49.4 \(\pm\) 1.9 mg/g at pH 7.0 \(\pm\) 0.9, which is about eight times higher than with the commercially used methods [81]. The regeneration studies showed that the regenerated imprinted polymers were effective for 10 cycles by washing with 0.01 M HNO\({}_{3}\). Recently, IIP@SiO2@Fe3O4 was applied as a new nanoparticle for As(V) adsorption [82]. According to the results of this study, the optimum conditions were a pH of 5.3, a contact time of 102 min, and an adsorbent dose of 2.3 g/L. Under these conditions, an adsorption capacity of 104.7 mg/g was achieved through physical and spontaneous endothermic absorption, as shown in the respective thermodynamics study. IIP@SiO2@Fe3O4 was synthesized in order to obtain a larger surface area and more adsorption sites, due to SiO2 nanoparticles (NPs). Ethylene glycol dimethacrylate (EGDMA), 4-vinylpyridine (4-VP), azobisisobutyronitrile (AlBN), and As (NO3)5 were used as the ligand, cross-linking agent, functional monomer, initiator and template ion, respectively. The specific surface area of IIP@SiO2@Fe3O4 was 610.99 m\({}^{2}\)/g and the porosity was 0.1163 cm\({}^{3}\)/g. However, one drawback of this material was that regeneration studies using 0.5 M of EDTA solution showed that after 4 regeneration cycles, the removal efficiency dropped significantly and only accounted for about 59.7%. Another attempt was based on the formation of a mesoporous As(V) ion-imprinted polymer (M-IIP), which was successfully prepared with \"one-pot\" co-polycondensation [83], by using 3-[2-(2-aminoethylamino) ethylamino] propyltrimethoxysilane (AAAPTS) as the functional monomer and diethylenetriamine (DETA) as the functionalized ligand. The synthesized M-IIP, proposed by [PERSON] et al. in 2022 [83], provided an excellent adsorption capacity of 78.74 mg/g at a pH of 3 and showed no noticeable change with the increase in temperature. Moreover, after 6 cycles washed with dilute HCl, the adsorption capacity of M-IIP can be maintained for up to 93% of the first cycle. Furthermore, in a parallel study by [PERSON] et al. in 2022 [84], an As(V) ion surface-imprinted polymer (S-IIP) was effectively formed on the surface of nano-SiO2, also using 3-[2-(2-aminoethylamino) ethylamino] propyltrimethoxysilane (AAAPTS) and applying it successfully in river water, tap water, and mineral water, with a recovery rate of between 98 and 100%. Below a pH of 3, the adsorption capacity could be up to 39.5 mg/g, which can be sustained at 75% after 4 adsorption-desorption cycles. Moreover, as the pH increased, the adsorption capacity decreased due to the various forms of arsenate in the different pH values and the variations of the surface charge of the adsorbent. Specifically, the adsorption capacity of 39.5 mg/g at pH 3 was about 12.1 mg/g at a pH of 7 [84].