Hydrogen bond driven deep eutectic solvent strategy for enhanced sludge dewatering via protein network remodeling

Area of Science:

• Environmental Science
• Chemical Engineering
• Materials Science

Background:

• Extracellular polymeric substances (EPS) in activated sludge retain water, hindering dewatering.
• Hydrogen bonds within EPS proteins are crucial for water retention.

Purpose of the Study:

• To synthesize and apply a deep eutectic solvent (DES) for enhanced activated sludge dewatering.
• To elucidate the mechanisms of DES-induced changes in EPS structure and protein conformation.

Main Methods:

• Synthesis of a DES from choline chloride and ferric chloride hexahydrate.
• Spectroscopic analysis (FTIR, CD) and density-functional theory (DFT) calculations.
• Sludge dewatering performance evaluation (capillary suction time, contact angle).

Main Results:

• Optimal DES treatment reduced capillary suction time by 58%.
• DES disrupted sludge floc structure, neutralized surface charge, and increased hydrophobicity (contact angle from ~10° to >35°).
• DES altered protein secondary structure (reduced α-helix, increased β-sheet) and weakened EPS binding capacity.

Conclusions:

• DES treatment effectively enhances sludge dewatering by modifying EPS structure and protein conformation.
• Non-covalent interactions by DES disrupt protein backbone hydrogen bonds, promoting hydrophobic residue exposure.
• This hydrogen bond-regulating strategy presents a green and efficient method for sludge dewatering and resource recovery.