Amphiphilic Thiol Polymer Nanogel Removes Environmentally Relevant Mercury Species from Both Produced Water and Hydrocarbons

Abstract

Technologies for removal of mercury from produced water and hydrocarbon phases are desired by oil and gas production facilities, oil refineries, and petrochemical plants. Herein, we synthesize and demonstrate the efficacy of an amphiphilic, thiol-abundant (11.8 wt % S, as thiol) polymer nanogel that can remove environmentally relevant mercury species from both produced water and the liquid hydrocarbon. The nanogel disperses in both aqueous and hydrocarbon phases. It has a high sorption affinity for dissolved Hg­(II) complexes and Hg–dissolved organic matter complexes found in produced water and elemental (Hg0) and soluble Hg–alkyl thiol species found in hydrocarbons. X-ray absorption spectroscopy analysis indicates that the sorbed mercury is transformed to a surface-bound Hg­(SR)2 species in both water and hydrocarbon regardless of its initial speciation. The nanogel had high affinity to native mercury species present in real produced water (>99.5% removal) and in natural gas condensate (>85% removal) samples, removing majority of the mercury species using only a 50 mg L–1 applied dose. This thiolated amphiphilic polymeric nanogel has significant potential to remove environmentally relevant mercury species from both water and hydrocarbon at low applied doses, outperforming reported sorbents like sulfur-impregnated activated carbons because of the mass of accessible thiol groups in the nanogel.

Aqueous microgels with engineered hydrophobic nano-domains

“…While the most commonly used cross-linker in microgel synthesis is N,N′-methylenebisacrylamide (BIS or MBA), which shows moderate-to-good solubility in water with increasing temperature, there are also many protocols for microgel synthesis using the significantly more hydrophobic cross-linking agents ethylene glycol dimethacrylate (EGDMA) [43][44][45][46][47] and divinyl benzene (DVB). 44,48 As crosslinking agents applied in the formation of covalent crosslinks in the microgel structure act as comonomers, their hydrophobicity can strongly influence the polymerization process leading to reduced incorporation of functional comonomer(s) of different solubility or lower particle formation rates. 49 In addition, the type of cross-linking agent influences the microgel morphology, rigidity and radial distribution of the polymer volume fraction as a result of different polymerization rates or decreased solubility.…”

“…the removal of harmful materials. In this context, the target of scavenging may vary from (i) heavy metals in waste water treatment, 48 to (ii) toxins, e.g. in the digestive system, 101 and (iii) food contaminants.…”

Preparation and use of nanogels as carriers of drugs

“…Nanogels swell in an acidic aqueous solution but shrink in an alkaline solution. Zhang et al (2021) adopted the microemulsion polymerization method and introduced a high density of thiol groups into the polymer gel to obtain disulfide polymer nanogels. After forming the nanogels, the disulfide and tributyl phosphine (Bu 3 P) were reduced to mercaptan groups to obtain the thiol polymer nanogels.…”

“…Matyjaszewski and coworkers (Zhang et al, 2021) synthesized poly(ethylene glycol) methacrylate monomethyl ether ester (OEOMA) nanogels using atomic transfer radical polymerization (ATRP) in a microemulsion system with the disulfide serving as the crosslinking point. Compared with conventional reversed microemulsion polymerization, the nanogels synthesized by using active free radicals have higher colloidal stability, narrower and more uniform distribution of size, and a more controllable structure and composition.…”

Amphiphilic micro‐ and nanogels: Combining properties from internal hydrogel networks, solid particles, and micellar aggregates

“…Using this strategy, Lowry and colleagues reported amphiphilic nanogels containing hydrophilic thiols for mercury removal applications. 222 Taking advantage of the disulfide chemistry, they first synthesized hydrophobic nanogels based on DVB and bis(2-methacryloyl) oxyethyl disulfide in a minemulsion copolymerization. In a second step, the disulfide bonds were reduced with tributyl phosphine to obtain free thiol groups (Figure 24).…”