Application of bio-alkyd resin for the removal of crystal violet and methylene blue dyes from wastewater

A new bio-alkyd resin containing carboxylated carbon, prepared from the biomass of olive trees, was successfully synthesized and characterized. X-ray diffraction results indicated that the sorbent has some crystals with an average crystallite size of 26.21 nm. The sorbent has an acidic character, which is mainly governed by carboxylic groups (1.7 mmol/g) and contains 71.16% carbon and 28.84% oxygen, as revealed by EDX analysis. The sorption behavior of methylene blue and crystal violet from aqueous solution onto the sorbent was investigated under various experimental conditions. Higher removal percentages of the dyes (90–96%) were observed at pH ranges of 5–6.5 and 9.5–11. The experimental sorption data showed a good correlation with the Langmuir isotherm model and the maximum monolayer sorption capacity to crystal violet and methylene blue were 289.3 and 310.3 mg g−1, respectively. The surface electrical conductivity value of the sorbent (σ = 0.27 × 10−6 Ω−1 cm−1) decreased after the sorption of CV and MB to 0.03 × 10−6 and 0.0075 × 10−6 Ω−1 cm−1. The sorption kinetic data were best described by the pseudo-second-order equation. The sorption of crystal violet was an endothermic process unlike that of methylene blue. Both dyes were removed from wastewater with satisfactory results. The limits of detection and quantitation were 2.0–2.6 and 3.5–4.9 and 6.8–8.5 and 11.7–16.2 μg L−1 for CV and MB, respectively. The relative standard deviation (RSD%, n = 6) values were in the range of 1.00–2.2%.