ADSORBENT FOR EFFICIENT REMOVAL OF MERCURY(II) FROM AQUEOUS SOLUTION

Enhanced adsorption of acid Blue-25 dye onto chitosan/porous carbon composite modified in 1-allyl-3-methyl imidazolium bromide ionic liquid

In this study, chitosan/porous carbon composite (C-PC) modified in 1-Allyl-3-methyl imidazolium bromide [AMIM][Br] under airtight condition was prepared for the removal of Acid Blue-25 dye (AB-25) from aqueous medium. For comparison of adsorption efficiency of C-PC, chitosan-activated carbon composite (C-AC) was also prepared in 1% acetic acid. The adsorbents were characterised using SEM, EDX, XRD, BET, TGA and FTIR. The micrograph of C-PC revealed cavities and slightly rough surfaces dominated with similar sized and irregular shaped stone-like materials which differ from the precursors' micrograph. BET analysis revealed the domination of mesopores on the C-PC and C-AC surfaces, as the hydroxyl and amino group on C-PC are the main active sites for AB-25 dye uptake. The dye was better adsorbed onto C-PC at pH 2 and C-AC at pH 4. The adsorption capacity obtained for C-PC, C-AC, activated carbon (AC) and chitosan (CH) using Langmuir isotherm model are 3333.33 mg/g, 909.90 mg/g, 909.09 mg/g and 833.33 mg/g, respectively. The experimental data are well described by Langmuir and Fruendlich isotherms for adsorption of the dye onto C-PC, AC and CH. C-AC fitted into Langmuir isotherm only. The kinetics of the adsorption fitted into pseudo-second order indicating the possibility of chemical interactions in the adsorption process.

[SnS4]4- clusters modified MgAl-LDH composites for mercury ions removal from acid wastewater

The high acidity of mercury ions (Hg²⁺) contained wastewater can complicate its safe disposal. MgAl-LDHs supported [SnS₄]^4- clusters were synthesized for Hg²⁺ removal from acid wastewater. The active sites of [SnS₄]^4- clusters were inserted into the interlayers of MgAl-LDHs using an ion-exchange method. The experimental results indicated that [SnS₄]^4-/MgAl-LDHs composite can obtain higher than 99% Hg²⁺ removal efficiency under low pH values. The maximum mercury adsorption capacity is 360.6 mg g^-1. It indicated that [SnS₄]^4- clusters were the primary active sites for mercury uptake, existing as stable Hg₂(SnS₄) on the surface of the composite. Under low pH values, such a composite seems like a "net" for HgSO₄ molecules, exhibiting great potential for mercury removal from acid solutions. Moreover, the co-exist metal ions such as Zn²⁺, Na⁺, Cd²⁺, Cr³⁺, Pb²⁺, Co²⁺, and Ni²⁺ have no significant influences on Hg²⁺ removal. The adsorption isotherms and kinetics were also studied, indicating that the adsorption mechanism follows a monolayer chemical adsorption model. The [SnS₄]^4-/MgAl-LDHs composite exhibits a great potential for Hg²⁺ removal from acid wastewater.