This study was set to study the effects of surfactants on crops using Triton X-100, one of widely used surfactants for various purposes including agricultural uses, as a target surfactant. The effects of Triton X-100 on the growth of wheat and lettuce were studied and the germination and shoot growth of wheat were not significantly affected by Triton X-100. With lettuce, the increasing Triton X-100 concentrations tend to negatively affect the growth, possibly due to the absorption of Triton X-100 by lettuce. The average lettuce fresh mass was reduced by 31% when Triton X-100 concentration increased from 0 to 240 mg L−1. This may mean that chemicals dissolved or mobilized by Triton X-100 can be absorbed by lettuce. The Cd mobilization was facilitated with Triton X-100, and the absorption of procymidone in soil by lettuce was greater when Triton X-100 was applied (i.e., 0.18 mg kg−1) than when water was applied (i.e., 0.15 mg kg−1), although they were statistically not different (p-value > 0.05). The average lettuce masses in the presence of residual procymidone in soil and Triton X-100 (16 g) were lower than that of the control soils (20 g), although they were statistically not different (p-value > 0.05). The results suggest that surfactants contained in pesticide formulations can potentially affect crop growth and absorption of other contaminants. Therefore, the residual surfactants and active ingredients in pesticide formulations need to be properly managed to protect the environment and to produce crops free of contaminants.

The potassium (K) sorption characteristics with three adsorbents, natural zeolite, ammonium acetate-treated zeolite, and manganese nodule, were studied and compared to see the potential use of manganese nodule as an alternative K adsorbent. In general, the Langmuir isotherm could fit the K sorption in the KCl solutions at different pH conditions better than the Freundlich isotherm. Based on the Langmuir parameters, the maximum K sorption was greater for the zeolite-based adsorbents (i.e., 40–42 mg g−1) than the manganese nodule (i.e., 2.0 mg g−1) at acidic conditions, while the manganese nodule (i.e., 9.7 mg g−1) showed better K sorption at neutral conditions. With the seawater samples, the zeolite-based adsorbents showed higher K recovery (4–14%) than the manganese nodule (0–8.8%). The K sorption on the zeolite-based adsorbents followed the pseudo-second-order kinetics and the K sorption rates were higher for the treated zeolite than the natural zeolite. The repeated sorption tests showed that the natural zeolite could potentially be reused up to three times without any significant loss of K sorption capacity, while the ammonium acetate-treated zeolite lost its K sorption capacity after the single sorption test. Overall, the results show that the manganese nodule may potentially be the alternative to zeolite for K recovery under certain conditions, yet the zeolite-based adsorbents are generally better than the manganese nodule. Thus, more studies to enhance the K recovery using zeolite, including surface modified zeolite, are recommended.

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