Evaluation of factors affecting tetracycline and diclofenac adsorption by agricultural soils using response surface methodology

Abstract

The adsorption process of the pharmaceutical pollutant in the soil is affected by its physicochemical properties and soil properties. In this study, the factors affecting the adsorption of tetracycline and diclofenac onto two different soils (S and M) were investigated using response surface methodology (RSM). The RSM design was used to optimize the five variable factors (pH (2–10), contact time (5–180 min), soil amount (1–10 g/L), temperature (25–45°C)) on the adsorption of tetracycline and diclofenac. The predicted optimal conditions obtained by RSM showed that pH was the most important variable affecting the adsorption of tetracycline and diclofenac. The optimum pH for the adsorption of tetracycline and diclofenac onto the soil samples S and M were found to be 4 and 2, respectively. The adsorbed amounts of tetracycline and diclofenac onto the soils S and M were calculated to be 14.82 mg/g, 12.43 mg/g, 189.40 mg/g, and 144.81 mg/g, respectively. In addition, the effects of soil organic matter, salt, and divalent cations on the adsorption of tetracycline and diclofenac onto soils were studied. The removal of soil organic matter slightly increased tetracycline adsorption, while inhibiting diclofenac adsorption. The presence of salt and divalent cations prominently suppressed the adsorption of tetracycline and diclofenac onto soils. A possible complex mechanism was proposed for TC and DCF adsorption, including ion exchange, electrostatic interaction, and some chemical bonds.

Mobility of antipyretic drugs with different molecular structures in saturated soil porous media

“…It has been conrmed that the electrostatic interactions (via negatively charged soil particles and antipyretic molecules, see Table S1 †) contributed notably to the mobility and deposition of drugs in porous media. 21,22,43 Note that most parts of the carboxyl groups (∼99.7%, Fig. S2 †) deprotonated under neutral conditions in this work due to the low pK a (∼4.5, Table 1) of IBF and IMC.…”

“…, temperature, pH, and ionic strength) also influenced the transport and deposition of drugs. 19–22 For example, Biel-Maeso et al investigated the transport of contaminants of emerging concern ( i.e. , ibuprofen and diclofenac) in soil columns under water saturated conditions.…”

“…18 Additionally, the compositions of soils (e.g., clay and soil organic matter contents) and surrounding environmental factors (e.g., temperature, pH, and ionic strength) also inuenced the transport and deposition of drugs. [19][20][21][22] For example, Biel-Maeso et al investigated the transport of contaminants of emerging concern (i.e., ibuprofen and diclofenac) in soil columns under water saturated conditions. They found that the highest concentrations were detected in the topmost layers for contaminants in the soil column with higher clay content, whereas vertical proles were more uniform in those with lower clay content.…”