# Application of Date Palm Tree Branch-Based Activated Carbon for Aqueous Toxicity Reduction
## 2 Materials and Methods  
All chemicals used for the present study were of high-purity reagent-grade quality. The major chemicals included phenol/C\({}_{6}\)H\({}_{5}\)OH (Riedel-de-Haen), \(p\)-cresol/C\({}_{6}\)H\({}_{4}\)CH\({}_{3}\)OH (FISHER), potassium dihydrogen phosphate/KH\({}_{2}\)PO\({}_{4}\) ([PERSON]), HClO\({}_{4}\) (BAKER), NaOH (FISHER), pH calibration standards (FISHER), copper calibration standards (BDH), ethanol ([PERSON]), nitrogen gas (99.999%), helium gas (99.999%), and high-purity liquid nitrogen (at 77 K). Date palm tree branches obtained from a local source were first trimmed, cut into smaller pieces, and then mixed with phosphoric acid solutions of 20, 40, and 60% (\(w/w\)) at impregnation ratios [R (volume-acid/weight-CB)] of 2 and 2.4. The soaking time was 1 h. Each sample prepared a specific set of conditions (out of the above-mentioned variables) was then transferred into stainless steel tubes (25 mm inner diameter and 300 mm length) via screw-type end caps. The tubes also had two narrow ports of 1 mm diameter at both ends to expel any reaction gasses. The tubes were then transferred inside a muffle furnace (AWF 12/42 Muffle Furnace, Lenton, UK) which was gradually heated at a rate of 5 \({}^{\circ}\)C/min up to the desired hold temperature value which was then maintained for a hold time value of 1 h. The hold temperature values were 500, 600, and 700 \({}^{\circ}\)C. At the end of each individual run, the respective sample was transferred to a desiccator and upon cooling, was subjected to thorough washing using deionized water until the wash-water showed pH \(\approx\) 7; the pH analyses were completed using a pH meter setup (ORION, La Verne, CA, USA) that was also regularly calibrated using the pH calibration standards. The washed samples was completely drained and then dried in an oven (750F ISO Temp Oven, FISHER, Waltham, MA, USA) at 120 \({}^{\circ}\)C. At all times, the samples were stored in enclosed containers to avoid any cross-contamination. The Brunauer-Emmett-Teller or BET specific surface area (\(SSA_{BET}\)) values for the produced GAC samples were determined at 77 K using an automatic specific surface area analyzer (ASAP 2020, MICROMETICS, Norcross, GA, USA) and high-purity nitrogen gas/liquid. Phenol was analyzed using a UV-Vis spectrophotometer (UV-1601 PC, SHI-MADZU, Kyoto, Japan). An appropriate sample volume was transferred into the UV-Vis test cuvette, and to this two drops of phosphate (KH\({}_{2}\)PO\({}_{4}\)) buffer solution were added. After this, the sample was transferred to the UV-Vis spectrophotometer and absorbanceat 269 nm wavelength was noted. The UV-Vis spectrophotometer was calibrated, using specific phenol standards, before each regular analysis. _p_-Cresol analysis was also completed using the same UV-Vis Spectrophotometer setup at an absorbance wavelength of 270 nm, with the rest of the procedure being similar to phenol analysis. Copper was analyzed employing an atomic absorption spectrophotometer setup (AVANTA, GBC, Regents Park, NSW, Australia). The AAS setup was always calibrated using the respective metal species standards. For each adsorption isotherm experiment, a set of clean glass bottles (of equal and appropriate size) was first arranged. After this, GAC quantities typically between 0 and 1.0 g per 100 mL solution were transferred to the individual glass bottles. A blank sample bottle with no GAC was also always included to account for any pollutant loss for reasons other than adsorption. Batches of synthetic wastewater samples were prepared using high-purity water (CORNING Mega PureTM System, Nicholasville, KY, USA) and stock solutions of the respective chemicals. Each bottle for the respective adsorption isotherm experiment was then filled with 100 mL of the target pollutant synthetic wastewater.