Introduction: Today, due to the lack of water and the special role of water in the daily lives of humans, the problem of water resources pollution is a very important environmental problem. Pollutions are usually due to the entry of different pollutants into water resources, especially rivers, which is a serious risk for human health and especially aquaculture. Organic pollutants are common water pollutants because of their great use in various industries and also because of the high solubility of some them in water, which are mainly toxic. Different methods are used to remove organic compounds from water with some advantages and disadvantages. One of the efficient techniques for wastewater treatment and removal of pollutants is the process of adsorption, which has been particularly considered for large -scale applications due to its ease of implementation as well as the diversity of adsorbents and low relative costs. One of the challenges of using the adsorption process is separating the adsorbent at the end of the process, and today, the use of magnetic adsorbents is a solution to this challenge. In the present study, the separation and removal of violet crystal dyes from aqueous environments using nickel ferrite magnetic nanoparticles (NiFe2O4), as adsorbent, has been investigated.
Materials and Methods: Violet crystal dye is used as a common dye pollutant and chemicals including ammonia, nicrate nitrate, iron nitrate to synthesize nano-nickel ferrite. Transmission electronic microscopy, X-rays spectroscopy, thermal decomposition and infrared spectroscopy, and UV-VIS spectrropotometer methods were used to characterize Nano-nickel ferrit. In this study, the effect of different parameters such as pH, initial dye concentration, adsorbent weight and adsorbent contact time with dye solution on adsorption process was tested. The relevant magnetic nanosorbent is synthesized by the co-precipitation method and a certain amount of it is added to the solution for use in the process. After the process is completed, sampeling is taken and the used adsorbent is easily separated from the aqueous environment using a magnet.
Results: The adsorbent identification results showed that the synthesized adsorbent of nickel ferrite particles was magnetic and based on transmission electron microscopy results and Debye-Scherer calculations from X-ray diffraction results, the size of synthesized nanoparticles were about 15 nm. The results of this study showed that for the initial concentration of 10 mg/l at pH = 8 and the adsorbent value of 0.05 g in 50 ml for 90 minutes, the dye removal efficiency is about 95 %. 
Discussion: The dimensions of the synthesized particles are in the nanometer range, which provides high adsorption properties for adsorbent. According to the results, the percentage of violet crystal removal by the magnetic nickel ferrite adsorbent is sensitive to the pH of the water and the removal of the dye in the alkaline environment is better than the acidic. Nickel ferrite is a good adsorbent that can be used to remove violet crystals from contaminated water. One of the benefits of this method is the magnetic property of nickel ferrite because being magnetic makes it easy to separate the adsorbent from the aqueous environment by the magnet.