Vol.:(0123456789) 1 3 Biomass Conversion and Biorefinery https://doi.org/10.1007/s13399-021-01718-0 ORIGINAL ARTICLE Adsorptive removal of polycyclic aromatic hydrocarbons from contaminated water by biomass from dead leaves of Halodule uninervis: kinetic and thermodynamic studies Adeola Akeem Akinpelu 1  · Mazen K. Nazal 1  · Nabeel Abuzaid 1 Received: 25 April 2021 / Revised: 20 June 2021 / Accepted: 29 June 2021 © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2021 Abstract Polycyclic aromatic hydrocarbons are carcinogenic organic pollutants that are produced primarily by daily industrial and personal activities. This work studies the use of an abundant seagrass powder (SG) as an adsorbent to remove the relatively highly soluble PAHs (i.e., Acenaphthylene (Ace), Phenanthrene (Phen), and Flouranthene (Flu)) from contaminated water. At an optimum dose of 2 g/L, Flu was found to have the highest removal efciency of 90.54%, followed by Phen with a removal efciency of 87.89% and Ace with an efciency of 61.11%. Flu had a maximum adsorption capacity of 2.25 mg/g at an equilibrium time of 6 h, followed by Phen with q e of 2.12 mg/g at an equilibrium time of 24 h, and fnally Ace with q e of 1.13 mg/g at an equilibrium time of 120 h. Linear and non-linear isotherm Langmuir, Freundlich, and Temkin models ft largely well with adsorption data for Flu, Phen, and Ace. This suggests that coexistence of heterogeneous adsorption mechanism. The kinetic data of all 3 PAHs were best described by the pseudo-second-order model. The adsorption of both Flu and Phen by SG was observed to be spontaneous with negative ΔG values. On the other hand, the adsorption of Ace was spontaneous only at a low temperature. The change of enthalpy (ΔH) for all the studied compounds was negative; therefore, their adsorption was found to be exothermic. Physisorption appeared to dominate the adsorption mechanism of Flu and Phen, with ΔH values of − 36.03 kJ/mol and − 36.65 kJ/mol respectively. However, Ace adsorption showed some presence of chemisorption, with ΔH values of − 114.43 kJ/mol. Keywords Water treatment · Adsorption isotherms · Biomass · Adsorption kinetics · Polycyclic aromatic hydrocarbons (PAHs) 1 Introduction The current and future consequences of pollution are threats to our existence. Our environment sufers from contami- nation by organic pollutants, such as polycyclic aromatic hydrocarbons (PAHs), at a rate that cannot be mitigated by nature [1]. Unfortunately, many solutions designed to heal these wounds and reverse this trend often come with scars that are more virulent than the wounds [2]. Therefore, it is sensible to attempt to mitigate the efects of pollution using natural residual products to heal nature. For this reason, this study investigates the use of dead seagrass leaf powder (SG) to remove PAHs from contaminated water. PAHs are carci- nogenic and mutagenic organic pollutants containing two or more fused aromatic rings [3]. They are largely formed by incomplete combustion of organic matter. Their pres- ence in the air, water, sediment, and animal tissues are well- documented in the literature. They are extremely persistent in the environment, and hence can gradually accumulate in any matrix or environment [4]. PAHs, such as benzo(a)pyr- ene (BaP), are converted to a more carcinogenic metabolite known as benzo (a) pyrene diol epoxide. The metabolite forms can adduct with human DNA, changing its genetic coding. The new DNA adduct will lead to uncontrollable cell growth, otherwise known as a tumor or cancer [2]. Therefore, many agencies have subjected PAHs to stronger legislative control [5]. The United States Environmental Protection Agency (USEPA) has listed 16 PAHs as top priority pollutants. * Mazen K. Nazal mazennazal@kfupm.edu.sa 1 Center for Environment and Water, Research Institute, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia