Zein–humic nanocomposite for simultaneous chloride/iron removal and corrosion mitigation in MDEA gas sweetening

Chloride and dissolved iron impurities in amine-based gas-sweetening systems promote localized corrosion and increase solvent-management costs, yet adsorbents capable of stable operation in alkaline amine media are limited. Here, a biodegradable composite based on functionalized zein nanoparticles and leonardite-derived humic substances (FZNP-LHS) is developed for simultaneous chloride and iron removal from H 2 S/CO 2 -loaded methyldiethanolamine solutions, while mitigating carbon steel corrosion. Structural and spectroscopic analyses reveal a a predominantly amorphous, moderately mesoporous material enriched in oxygen- and nitrogen-containing functional groups, providing abundant accessible adsorption sites. The integrated contaminant-removal data were empirically described more accurately by the Freundlich equation than by the Langmuir equation, with a combined chloride-iron uptake of approximately 45–52 mg g⁻¹ under the investigated conditions. Multi-objective RSM-GA optimization achieves near-complete chloride removal (98%) and high iron removal (91%), accompanied by a consistent reduction in corrosion rate. Electrochemical and 45-day gravimetric measurements indicate measurable corrosion mitigation, accompanied by increased charge-transfer resistance, electrochemical behavior consistent with mixed-type inhibition, and reduced localized attack. Exploratory Random Forest analysis identified adsorption capacity and residual chloride concentration as variables most strongly associated with corrosion behavior. The composite retained approximately 85% of its working capacity over five adsorption–regeneration cycles, demonstrating promising short-term regeneration performance. Screening-level life-cycle and techno-economic analyses suggest competitive environmental and operating performance relative to benchmark materials.