Mechanochemical Synthesis of a Biphenyl dicarboxylic acid-Based Zinc Metal Organic Framework for Brilliant Blue Dye Removal: Optimization by Box–Behnken Response Surface Methodology

In this research, the optimization of Brilliant Blue dye (BBD) removal from aqueous solution was investigated using a zinc-based metal-organic framework (Zn-MOF) synthesized from 4,4-biphenyl dicarboxylic acid (BPDC) via a solvent-free mechanochemical approach using a mortar and pestle. The prepared adsorbent was characterized using Fourier Transform Infrared Spectroscopy (FTIR), Energy Dispersive X-ray Fluorescence (EDXRF), Brunauer–Emmett–Teller (BET) analysis, X-ray Diffraction analysis (XRD), Thermogravimetric Analysis (TGA) and pH point of zero charge (pHPZC) measurements to evaluate its structural features, elemental composition, surface properties, thermal stability and surface charge behavior. The BET surface area was 221.022 m²/g, the pHPZC was 6, and the material was stable up to 310 °C. Statistical optimization of the adsorption process was carried out using Response Surface Methodology based on the Box–Behnken design. The effects of pH, ionic strength, contact time, and adsorbent dosage were examined as independent process variables, while percentage dye removal served as the response. In this study, the initial dye concentration was set at 30 Mg/L, the Sorbate volume was 100 mL, and dye concentrations were determined using a Jenway 7315 spectrophotometer at 640 nm, as obtained from the spectra scan of the dye. The optimized conditions obtained were an adsorbent dosage of 0.473 g, an ionic strength of 0.0017 mol/L, a contact time of 34.66 min, and a pH of 2.12. Under these conditions, an experimental dye removal efficiency of 98.33% was achieved, which was in close agreement with the model-predicted value of 99.16%, indicating the suitability of the model for the optimization of Brilliant Blue dye adsorption in a synthetic wastewater system.