How Green nano zero valent iron compares to Industrial Iron nanoparticles in Driving Sustainable Hydrocarbon Bioremediation

Green nano-zero-valent iron (nZVI) has been promoted as an eco-friendlier alternative to industrial and chemically synthesised nZVI, yet direct comparisons of their chemical and biological performance remain scarce. This study evaluated both formulations in 100 ml microcosms containing diesel-contaminated freshwater. Triplicate batches received 0.004 mg/L, 0.01 mg/L, and 0.02 mg/L of either green nZVI (18.6 mg/L) or commercial nZVI (20 mg/L); untreated flasks served as controls. Chemical oxygen demand (COD) and gas chromatography–flame-ionisation detection (GC-FID) tracked total petroleum hydrocarbons (TPH) at two hours and 24 hours, while 16S-rRNA amplicon sequencing profiled microbial communities. Industrial nZVI delivered the fastest abiotic removal, cutting COD from 179 mg/l to 20 mg/l and TPH from 58 mg/l to 16 mg/l, reflecting a 73% reduction within 24 hours at 0.02 mg/L dosage. However, reactive-oxygen bursts depressed microbial abundance by approximately 25% relative to the 9,510 Operational Taxonomic Units (OTU) control. Green nZVI achieved slightly lower 24-hour removals (COD 49–68%; TPH 56–64%), but tripled biomass to 34,000 OTUs and selectively enriched hydrocarbon-degrading taxa, including Betaproteobacteria and Actinobacteria . Statistical tests confirmed a non-significant population decline for industrial nZVI (t = -2.52, p = 0.053) and a significant rise for green nZVI (t = 3.89, p = 0.012). Optimum performance occurred at the lowest green dose of 0.004 mg/L for both green and industrial nZVI, where TPH fell by 73% for Industrial nZVI and 64% for green nZVI, while the community expanded three-fold, bolstering synergistic nano-bio interactions. These findings demonstrate that plant-derived nZVI can rival industrial particles in hydrocarbon removal while enhancing microbial resilience, furnishing dose windows, contact-time targets, and monitoring benchmarks for sustainable nanobioremediation.