Color is the prime feature directly associated with the consumer’s attraction and choice of their food. The flavor, safety, and nutritional value of any food product are directly associated with the food color. Natural and synthetic colorants (dyes and pigments) have diversified applications in various sectors such as food, feed, pharmaceutical, textiles, cosmetics, and others. Concerning the food industry, different types of natural and synthetic colorants are available in the market. Synthetic food colorants have gained popularity as they are highly stable and cheaply available. Consumers worldwide prefer delightful foodstuffs but are more concerned about the safety of the food. After its disposal, the colloidal particles present in the synthetic colorants do not allow sunlight to penetrate aquatic bodies. This causes a foul smell and turbidity formation and gives a bad appearance. Furthermore, different studies carried out previously have presented the toxicological, carcinogenic effects, hypersensitivity reactions, and behavioral changes linked to the usage of synthetic colorants. Natural food colorings, however, have nutraceutical qualities that are valuable to human health such as curcumin extracted from turmeric and beta-carotene extracted from carrots. In addition, natural colorants have beneficial properties such as excellent antioxidant properties, antimutagenic, anti-inflammatory, antineoplastic, and antiarthritic effects. This review summarizes the sources of natural and synthetic colorants, their production rate, demand, extraction, and characterization of food colorants, their industrial applications, environmental impact, challenges in the sustainable utilization of natural colorants, and their prospects.

Fe₃O₄@SiO₂-NH₂ core-shell magnetic nanoparticles were developed by a rapid one-step precipitation route followed by reverse microemulsion and amine functionalization. In this study, an Fe₃O₄@SiO₂-NH₂ nanoparticle was used to evaluate its adsorption efficiency for the treatment of a synthetic solution of Cd(II) ion. The structural and physicochemical properties of Fe₃O₄@SiO₂-NH₂ nanoparticles were characterized by XRD, SEM-EDAX, TEM, FTIR and TGA. From the TEM analysis, the morphology of Fe₃O₄@SiO₂-NH₂ was found as 100–300 nm. In TGA, the first weight loss was noticed between 373 and 573 K, the second was between 673 and 773 K and the final weight loss took place above 773 K. Batch experimental tests, such as pH, dosage of Fe₃O₄@SiO₂-NH₂, Cd(II) ion concentration, temperature as well as interaction time, were conducted and evaluated. Experimental study data were used for the non-linear forms exhibited by isotherms and kinetics of the sorption procedure. The equilibrium adsorption observations were adequately combined with pseudo-first-order kinetics as well as Freundlich isotherm. Monolayer maximum adsorption capacity was found to be 40.02 mg/g, recorded at pH 6 with an interaction time of 30 min, temperature of 303 K and sorbent dose of 2.0 g/L. The thermodynamic study indicated that the adsorption process was an exothermic, spontaneous reaction (−∆o^o = −15.46–7.81 (kJ/mol)). The as-synthesized sorbent had excellent recyclability, and its adsorption efficiency was maintained after five cycles of reuse. The findings of the study exhibited the magnetic Fe₃O₄@SiO₂-NH₂-nanoparticle as an alternative effective adsorbent in eradicating Cd(II) ions from aqueous solution.