In　this　study,　sulfur-doped　iron-based　carbon　materials　were　synthesized　by　calcining　Fe-MOF　derivative　precursors　modified　with　sodium　lignosulfonate　(SL)　during　a　solvothermal　process.　Characterizations　including　SEM,　TEM,　XRD,　BET,　and　XPS　confirmed　that　SL　incorporation　introduced　sulfur　doping　and　a　carbon　substrate,　enhancing　the　specific　surface　area,　electrical　conductivity　and　catalytic　activity　of　the　electrocatalysts.　The　materials　were　applied　as　cathodes　in　a　heterogeneous　electro-Fenton　(HEF)　system　to　remove　oxytetracycline　hydrochloride　(OTC),　and　the　degradation　mechanism　was　further　investigated.　Among　the　synthesized　materials,　FeNPs/CS1.5　(the　catalyst　prepared　when　both　iron　salt　and　organic　ligand　were　used　in　an　amount　of　6.0　mmol　and　sodium　lignosulfonate　was　added　in　an　amount　of　1.5　mmol)　exhibited　the　best　performance,　achieving　over　95　%　OTC　removal　and　a　mineralization　rate　of　78.2　%　under　optimal　conditions　(SL　to　Fe(NO3)3·9H2O　atomic　weight　ratio　of　1:4,　catalyst　loading　of　2.5　mg　cm−2,　voltage　of　−1.2　V　and　pH　=　6).　Mechanistic　studies　revealed　that　OTC　degradation　occurred　through　both　radical　(•OH,　O2•-,　SO4•-)　and　non-radical　(1O2,　electron　transfer)　pathways.　Additionally,　SL　improved　electron　transfer　rates,　promoted　the　Fe(II)/Fe(III)　redox　cycle,　and　significantly　inhibited　iron　ion　leaching.　These　results　demonstrate　the　potential　of　SL-modified　catalysts　for　efficient　pollutant　removal　and　their　practical　applicability　in　real　water　treatment　systems.　©　2025