A study of the adsorption and removal of Sb(Ⅲ) from aqueous solution by Fe(Ⅲ) modified Proteus Cibarius with mechanistic insights using response surface methodology

Environmental pollution caused by excessive Sb(Ⅲ) in the water environment receives more and more attention. We investigated the effect, interaction and mechanism of processing parameters on the removal of Sb(Ⅲ) by an adsorbent which using an iron salt modified biosorbent (Fe(Ⅲ) modified Proteus Cibarius (FMPAs)). Our study evaluated the optimisation of the adsorption time, adsorbent dose, pH, temperature and the initial concentration of Sb(Ⅲ). We use response surface methodology to optimize this process. The optimal conditions were determined, and the adsorption isotherm model, the adsorption kinetics model and the adsorption mechanism were also evaluated. The results showed that: (1) The optimal condition for the adsorption of Sb(Ⅲ) by FMPAs were adsorption time 2.2 h, adsorbent dose 3430 mg/L, pH 6.0, temperature 44.0℃ and the initial concentration of Sb(V) 27.70 mg/L, the removal rate of Sb(Ⅲ) reached 97.60%. (2) The adsorption process of Sb(Ⅲ) by FMPAs conforms to the Langmuir adsorption isotherm model, and its maximum adsorption capacity (qmax) is as high as 30.612 mg/g, Pseudo-first-order kinetic model can fit the adsorption process well, and the adsorption process can be classified as single layer adsorption and chemisorption. (3)The mechanism is via the hydroxyl group in Fe—O—OH and EPS—Polyose—O—Fe(OH)2, which forms a new complex Fe—O—Sb and X≡Fe-OH thereby removing Sb(Ⅲ). The study showed that FMPAs have higher adsorption capacity for Sb(Ⅲ). It is a green adsorbent with great potential for removal of Sb(Ⅲ) from water.