Efficient Mercury Removal from Wastewater via Carbonized Inverse Vulcanized Copolymers

Abstract

Inverse vulcanized polysulfides represent innovative sulfur-rich copolymers with unique properties that make them highly suitable for a variety of applications, including the effective remediation of Hg²⁺ contaminants. However, their inherent hydrophobicity and low surface area limit the Hg²⁺ uptake. This study introduces novel hydrophilic porous adsorbents, developed by carbonizing (with or without potassium hydroxide (KOH)) inverse vulcanized copolymers to enhance mercury removal efficiency from wastewater. Two copolymers were synthesized: one from sulfur (S) and methacrylic acid (MA) (Copoly(SMA)), and the other from S and vinyl benzyl chloride (VBC), later functionalized with N-methyl-d-glucamine (NMDG). Methacrylic acid and NMDG functionalization were introduced to enhance copolymer hydrophilicity with −OH groups. Carbonization in the presence of KOH significantly boosted surface area and pore formation, yielding a maximum surface area of 175.5 m²/g of the NMDG-functionalized carbonized copolymer (Copoly(SVBC)@NMDG_KOH_C)─68, 3.5, and 1.32 times greater than the uncarbonized, carbonized Copoly(SMA)_C, and KOH-aided carbonized Copoly(SMA)_KOH_C copolymers, respectively. Adsorption tests revealed a maximum mercury adsorption capacity of 572.4 mg/g (Langmuir) for Copoly(SVBC)@NMDG_KOH_C, underscoring its potential as a mercury adsorbent. Isotherm and kinetic analyses reveal that mercury uptake follows the Langmuir model, demonstrating monolayer adsorption, and fits well with pseudo-second-order kinetics, indicating chemisorption as the primary mechanism. Furthermore, economic analysis showed that mercury removal with this adsorbent is cost-effective at just $9.95 per gram of Hg removed from wastewater.