# Environmental Behavior and Remediation Methods of Roxarsone
## 6 Remediation Methods of ROX Contamination
### Adsorption  
Adsorption is cheap and simple and is an effective method for removing benzene arsenic acid compounds from aqueous solutions. Commonly used adsorption materials include metal oxides, nanomaterials, and metal-organic frameworks (MOFs).  
Materials based on iron and aluminum are often used to adsorb ROX. Aromatic organoarsenic compounds adsorb to adsorbent materials through the As-C bond on the benzene ring. The acidity of organoarsenical means arsenic-containing organic compounds strongly sorb to iron and alumina. The adsorption of ROX was carried out through the AsO\({}_{4}\)[3]- functional group [4]. ROX adsorbs similarly strongly to alumina and goethite, but there are fewer adsorption sites on alumina surfaces than goethite surfaces, meaning that the adsorption efficiency is lower for alumina than goethite [64]. Research into nanomaterials for adsorbing ROX has mainly focused on the synthesis of efficient organoarsenical-adsorbent, including multiwalled carbon nanotubes, iron, and aluminum nanomaterials. The O-H bond plays a major role in the adsorption process of ROX on multiwalled carbon nanotubes, and the increase in pH value and ionic strength would reduce the adsorption capacity of ROX on multiwalled carbon nanotubes [80].  
Researchers in China and abroad have recently been trying to develop new adsorbents or improve existing adsorbents to improve the removal efficiencies for ROX from water to allow the adsorbents to be used to prevent and remediate ROX pollution of the environment. The specific surface area and pore volume of montmorillonite are increased by modifying the montmorillonite with Fe/La, and the adsorbent was found to have a good affinity for ROX and an adsorption capacity of 32.82 mg/g [65]. More ROX was found to adsorb to goethite modified with humic acid than to unmodified goethite, and the maximum adsorption capacity of goethite modified with humic acid for ROX was 80.71 mg/g [81]. The adsorption process included diffusion through the outer liquid film, surface adsorption, and internal particle diffusion, but chemical adsorption was the key factor affecting the adsorption rate [81]. Fe\({}_{3}\)S\({}_{4}\) nanosheets have been used to adsorb ROX, and ROX was first transformed into HAPA through structural sulfide in the Fe\({}_{3}\)S\({}_{4}\) nanosheets and then the HAPA adsorbed to the Fe\({}_{3}\)S\({}_{4}\) surface [82]. This occurred more strongly at neutral to alkaline pH values than at lower pH values [82]. MOFs, such as MIL-100-Fe, can be used to remove organoarsenic compounds from contaminated water because of its high adsorption capacity, and rapid adsorption [83]. The maximum adsorption capacities of modified sorghum straw biochar for ROX, As(III), and As(V) were 12.4, 5.3, and 23.0 mg/g, respectively, and the adsorption behavior was described well by the Langmuir model and a quasi-second-order rate model [84]. The results described above indicate that continual improvements are giving adsorbents with increasing adsorption capacities for ROX that offer great promise for economically and efficiently remediating water contaminated with ROX.