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In the present study, the optimization of electrocoagulation (EC) conditions for the purification of olive debittering wastewater (ODW) was investigated by response surface methodology (RSM). For this purpose, a central composite design (CCD) was employed to optimize the process variables including current density (3.0–30.0 mA/cm2) and EC time (10.0–60.0 min). The results showed a significant effect of current density and EC time on the removal efficiency of total phenolic compounds (TPC) and chemical oxygen demand (COD). The best models obtained using the central composite design were quadratic polynomial for TPC (R2 = 0.993), COD (R2 = 0.982), and the inverse square root of turbidity (R2 = 0.926). Additionally, the square root of electrode consumption and energy consumption were appropriately fitted to the two-factor interaction (2FI) model (R2 = 0.977) and quadratic polynomial (R2 = 0.966) model, respectively. The predicted optimum conditions based on the highest removal efficiency for TPC were a current density of 21.1 mA cm−2 and an EC time of 58.9 min, in which the obtained model predicted 82.6% removal for TPC. This prediction was in agreement with the laboratory result (83.5%). The amount of energy consumption and the operating cost in these conditions was estimated to be 14.92 kWh and USD 6.49 m−3 per ODW, respectively.

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BACKGROUND Potentiometric detections based on ion‐selective electrodes offer the advantages of simplicity, speed, and low cost over other electrochemical methods. In this work, the preparation of a novel carbon‐paste electrochemical sensor containing the synthesized N‐(1‐(4‐bromophenyl)‐3‐oxo‐3‐phenylpropyl)acetamide is described. Multi‐walled carbon nanotubes (MWCNTs) were incorporated into the electrode composition to promote electron transfer reactions. The modified carbon paste electrode was evaluated as a selective sensor for the detection of chromium (III). RESULTS The prepared sensor showed nearly stable potentials in the pH range of 4.0–6.5, with a fast response time (<15 s). At the optimum conditions, the potentiometric method exhibited a linear response toward Cr(III) concentration in the range of 5.0 × 10−7 to 1.0 × 10−3 mol L−1 with a Nernstian slope of 19.5 ± 0.1 mV per decade and a detection limit of 3.1 × 10−7 mol L−1. CONCLUSION The proposed sensor possesses the advantages of good selectivity to Cr(III) and an improved detection limit compared to the results of some other studies. Better selectivity can be attributed to the ability of the ionophore to form a stable chelate with Cr(III) ions. The new Cr(III) sensor showed excellent stability over 8 weeks and its response time was comparable to other previously reported chromium ion‐selective electrodes (ISEs) . The simple, fast, and cheap synthesis method of ionophore provided other advantages for this study. The modified electrode was also used as a sensor for the end‐point detection in the potentiometric titration of Cr(III) against ethylenediaminetetra acetic acid (EDTA). © 2021 Society of Chemical Industry (SCI).