In this study, a novel hydrochar adsorbent derived from lotus seedpods was synthesized and subsequently modified to enhance its adsorption efficiency for quinoline contaminated wastewater. Using lotus seedpods as biomass raw material, lotus seedpod hydrochar (LSH) was prepared by hydrothermal carbonization method, and it was modified with hydrochloric acid (HA) and phosphoric acid (PA) as modifiers to improve adsorption efficiency. The adsorption kinetics and isotherms of quinoline on both the unmodified and modified hydrochars were studied in detail to elucidate the underlying adsorption mechanisms. Furthermore, the effect of coexisting organic pollutants, i.e. phenol and pyridine, commonly found in coking effluents, on the quinoline adsorption efficiency of hydrochar was investigated. The regenerative potential of the adsorbent was explored through desorption studies to assess the reusability and practicality of hydrochar post-adsorption. The optimal conditions for modified LSH were determined as follows: an adsorbent dosage of 3 g/L, pH of 3, an initial quinoline concentration of 200 mg/L, and a contact time of 90 minutes. The maximum adsorption capacities for PA-LSH and HA-LSH were 48.59 mg/g and 49.12 mg/g, respectively. Among the types of modification agents, acid modifiers, particularly 20 % phosphoric acid and 20 % hydrochloric acid, significantly enhanced the adsorption efficiency, increasing the adsorption rates by 24.24 % and 14.56 %, respectively, compared to unmodified hydrochar (64.06 %). Coexisting pollutants minimally affected quinoline adsorption, with phosphoric acid-modified hydrochar maintaining 80.33 % removal in simulated coking wastewater. Regeneration with hydrochloric acid showed improved utility, with modified hydrochar sustaining over 80 % adsorption after three cycles. This research not only presents an innovative approach to the development of efficient adsorbents for quinoline removal, but also provides insight into the adsorption behavior of hydrochar in the complex wastewater systems. The findings contribute to both the advancement of sustainable water treatment technologies and the use of biomass-derived materials for environmental remediation. As such, this work holds promise for applications in wastewater treatment and environmental remediation.