Revitalizing biopolymers to prepare temperature-resistant and salt-tolerant filtrate reducer by combining light-driven lignin depolymerization and subsequent photopolymerization on MIL-100(Fe)-NH₂(20) photocatalyst

For the first time, this study integrate the light-driven depolymerization/activation of industrial grade sodium lignosulfonate and its subsequent photo-induced radical polymerization with acrylamide (AM) and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) into one-pot using MIL-100(Fe)-NH₂(20) as a photocatalyst to synthesize fluid loss agent LSMP. Due to the significant hydrogen bonding effect, the agent owns excellent rheological and filtration properties. The filtrate volumes of drilling fluids containing 2.0 wt% agent before and after aging at 150 °C are only 3.6 and 4.6 mL, reducing by 85.0 % and 88.5 %, respectively, compared with pure fluids. Even at high temperatures and high salinity, LSMP still gives stunning performances with significant filtrate volumes decline of 96.58 % and 86.52 % under erosion of 25 wt% NaCl and 2.0 wt% CaCl₂, separately. Meanwhile, the filtration reduction mechanism of LSMP is presented, and the probable photocatalytic mechanism is also explored: 1, under depolymerization process, the selective cleavage of ubiquitous C - O/C - C linkage bonds (β-O-4, β-5, α-O-4, β-β, 4-O-5, β-1, dibenzodioxocin, etc.) occur, accompanied by the aromatic rings intact; 2, with the action of photo-induced carriers generated on MIL-100(Fe)-NH₂(20), absorbed photons are transformed into thermal energy and the radical polymerization of green synthesis are ultimately achieved.