Co-biosorption of copper and glyphosate by Ulva lactuca

This study investigated the adsorption of glyphosate (PMG) onto the green algae Ulva lactuca. PMG was not adsorbed by U. lactuca but PMG was adsorbed when the process was mediated by Cu(II) with molar ratios Cu(II):PMG ≥ 1.5:1.U. lactuca was characterized by water adsorption surface area, FTIR, SEM and EDS. The Langmuir and Freundlich models were applied. Results showed that the biosorption processes for copper and PMG in the presence of copper were described described by the Langmuir model (qmax = 0.85 ± 0.09 mmol g−1, KL = 0.55 ± 0.14 l mmol−1 and qmax = 3.65 ± 0.46 mmol g−1, KL = 0.103 ± 0.03 l mmol−1, respectively). Copper adsorption was greater in the presence of PMG than in the absence of the pesticide and the adsorption can only be represented by the Freundlich model (KF = 0.08 ± 0.01, 1/n = 1.86 ± 0.07).In all cases studied, the maximum metal uptake (qmax) increased with increasing pH. Surface complexes with a stoichiometry ranging from CuPMGCu to CuPMGCu3 are suggested as reaction products of the process.Due to the increasing amounts of PMG applied in Argentina, natural reservoirs present considerable amounts of this herbicide. The value of this work resides in using U. lactuca, a marine seaweed commonly found along coastlines all over the world, as a biosorbent for PMG.

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► A remediation technique for PMG in waters is proposed.
► The mechanism relies on PMG adsorption mediated by copper adsorption onto Ulva lactuca.
► PMG can be adsorbed by U. lactuca only when molar ratios Cu:PMG are ≥1.5:1.
► PMG adsorption occurs if the copper adsorption equilibrium is previously established.
► Biosorption of PMG in the presence of Cu(II) is well represented by Langmuir model.