One‐Pot Electrochemical Synthesis of Citric Acid Functionalized Iron Oxide Magnetic Nanoparticles for Congo Red Adsorption

Abstract

The organic dye pollutants originate from release of effluents from different industries such as printing, photographic, textile, organic dye manufacturing, paper-pulp, plastic, tannery, paint, and leather industries. [3] The accumulation of dyes in the water bodies negatively affects the marine life and human health due to their noxious and mutagenic effects. [4] Organic dyes like synthetic azo dyes which account for 60-70% of dyes consumption have detrimental potential to decline aquatic oxygen and hamper photosynthetic processes when released in water sources without treatment. [5] Furthermore, azo dyes also bioaccumulate in humans initiating harmful respiratory and neurological health effects. [6] The dye Congo red (CR) is a benzidine-based anionic diazo dye which has complex aromatic structure that makes it stable and non-biodegradable. [7] The biotransformation of CR could potentially develop carcinogenic benzidine and amine groups which are carcinogenic in nature. [8] CR removal from contaminated water faces various challenges because of its high water solubility, persistent nature, and complex chemical structure. Several biological, chemical and physical techniques have been established to treat CR containing wastewater such as membrane separation, photolysis and photocatalytic degradation, electrochemical processes, coagulation, adsorption, ozonation, ion exchange, ultrafiltration, oxidation, electrolysis and biodegradation. [9] Among several methods reported for the removal of water contaminants, adsorption is one of the widely used, well-established and convenient technique owing to its high efficiency, ease of operation, minimum energy requirements, lack of secondary pollution, low cost and reusability. [10] Adsorption is a physicochemical technique that includes accumulation of adsorbate on the adsorbent surface. [11] Multiple categories of nano-adsorbents like metal/metal oxides, fly ash, clays, activated carbon, carbon nanotubes, graphene/graphene oxide, zeolites, biochar, polymer composites, and metal-organic frameworks were reported over the years for withdrawal of CR from polluted water. [12] However, each of the adsorbent has its own drawbacks such as high cost, difficulty to reuse, and low surface area. [13] On that account, development of sustainable and efficient adsorbents for decolorization of dye wastewater is of great importance in environment protection. Azo dyes, likeCongo red (CR), are persistent contaminants that cause detrimental consequences on living organisms in various habitats. In the present study, a novel and facile one-pot citric acid functionalized iron oxide magnetic nanoparticles (Fe 3 O 4 @CA NPs) through an electrochemical method are synthesized and characterized for adsorbing CR dye present in an aqueous solution is reported. The influence of various factors on the adsorption of CR dye, namely pH of the CR solution, Fe 3 O 4 @CA NPs concentration, initial CR dye concentration, contact time, temperature, and agitation speed, are examined. The adsorption isotherms and...