Abstract
Some nitroaromatic compounds are found in wastewater from industries such as the weapons industry or the wine industry. One of these compounds is 3,5-dinitrosalicylic acid (DNS), widely used in various tests and frequently found as an emerging pollutant in wastewater and to which the required attention has not been given, even though it may cause serious diseases due to its high toxicity. This study investigated the adsorption of DNS using granulated activated carbon (GAC) and powdered activated carbon (PAC) at different temperatures. The results show that in equilibrium, the adsorption takes place in more than one layer and is favorable for the removal of DNS in both GAC and PAC; The maximum adsorption capacity was obtained at 45 °C, with values of 6.97 mg/g and 11.57 mg/g, respectively. The process is spontaneous and exothermic. In addition, there was a greater disorder in the solid-liquid interface during the desorption process. The predominant kinetics using GAC (7.14 mg/g) as an adsorbent is Elovich, indicating that there are heterogeneous active sites, and when PAC (10.72 mg/g) is used, Pseudo-second order kinetics predominate, requiring two active sites for DNS removal. External mass transfer limitations are only significant in GAC, and ATR-FTIR studies in PAC demonstrated the participation of functional groups present on the adsorbent surface for DNS adsorption.
Highlights
Water pollution has been a major problem worldwide for many years, causing serious health consequences for all living beings [1,2,3]
This study showed that one of the causes for which there is a greater adsorption capacity and percentage of removal of dinitrosalicylic acid (DNS) is the use of powdered activated carbon (AC), since it only depends on the participation of the functional groups that are found on the surface; for granulated activated carbon (GAC) it depends on the participation of the adsorbent surface but is limited by the effect of external mass transport, confirming that more energy must be used to remove the DNS from the solution compared to powdered activated carbon (PAC)
It was revealed that the adsorption process is carried out on the surface of the material without the limitation of having only a monolayer of interaction between the adsorbate and the adsorbent; this is likely attributable to the fact that the process is favored by the increase in temperature due to the endothermic nature of DNS adsorption
Summary
Water pollution has been a major problem worldwide for many years, causing serious health consequences for all living beings [1,2,3] This is due to the fact that several industrial processes produce large amounts of wastewater containing pesticides, pharmaceuticals, and heavy metals, among others [4,5,6]; In addition, other anthropogenic activities, such as urban or agricultural, together with the widely reported droughts of recent years, have caused a global water shortage [1], which is reflected in that more than 40% of the world’s population does not have access to drinking water [7]. AC is widely used in water treatment [1,6,11,12,13,17] because it has properties of interest such as high contact surface, porosity, and abundant surface groups [12] that are more stable compared to those that are found in clays, zeolites, and graphene-based adsorbents [11]
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