No abstract

The wet manufacturing process of the phosphoric acid plant generates a waste gas containing hydrogen sulfide (H 2 S), a malodorous and toxic gas. In this study, a new application, coupling the neutralization in potassium hydroxide (KOH) solution and the catalytic oxidation (designated as KOC), was developed to treat H 2 S. In fact, the waste gas of the phosphoric acid plant was neutralized in KOH solution in the presence of the air oxygen as an oxidizing agent and the activated carbon (AC) prepared from an agricultural waste, that is, the olive stone, as a catalyst. The process was efficient in both batch and cyclic configurations. The "KOC batch" process offers the retention of more than 40 mgS and allows high removal of H 2 S compared to absorption alone. The "KOC cyclic" process treated 800 mgS/g of AC.

The present work aimed at evaluating the performance of activated carbons (AC) derived from Tunisian olive stone in the removal of dissolved sulfides from synthetic and industrial solutions. The ACs were produced by physical (CAP) and chemical (CAC) activations and characterized by N2 adsorption–desorption, scanning electron microscope/X‐ray dispersive energy analysis, Fourier transform infrared spectrometer, and Boehm titration. The ACs dispose of well‐developed specific surface area (1100–730 m2/g) with dispersed oxygen surface groups. Batch adsorption test performed by synthetic sulfides solutions reveals significant adsorption capacities. The kinetic data were modeled using the pseudo‐first order, the pseudo‐second order, the intra‐particle diffusion, as well as the Boyd model. The results prove that sulfides adsorption is described by the pseudo‐second order equation. Moreover, the sulfides adsorption mechanism follows the intra‐particle diffusion and the external diffusion. The adsorption equilibrium data were modeled by Freundlich, Langmuir, Temkin, and D‐R models. The equilibrium data fitted the Langmuir model with monolayer adsorption capacities of 20.83 mg/g for CAP and 22.72 mg/g for CAC. In the dynamic test, the sulfides adsorption by ACs from industrial spent caustic solutions decreased to 2.81 and 7.32 mg of sulfides/g of CAC and CAP. Therefore, the adsorption process is not a promising treatment method for sulfides removal from the phosphoric acid plant wastewater.