Taguchi Optimization Study for Efficient Removal of Phenolic Pollutants from Wastewater Using Cu-Alanine Functionalized Graphene Oxide and Their Grafted Alginate Microbeads: Isotherm Modeling

摘要

In this work, an environment-friendly composite had been facilely synthesized using alanine functionalized graphene oxide (Cu-Aln/GO). After that, in-situ encapsulation for the produced aminated graphene oxide into the alginate polymer matrix was achieved to yield a promising Cu-Aln/GO@Alg hydrogel. The adsorption performance of these composites towards the removal of total organic phenols (TOPs) in wastewater was demonstrated with the assistance of the orthogonal array of Taguchi's L9 established on three-level factorial. The evaluated TOPs included phenol (Ph), 2-chlorophenol (2-CP), and 2,4 dichlorophenol (DCP). The synergistic effects on the adsorption behavior of different parameters, such as pH, adsorbent dose, and temperature, were statistically analyzed using MINITAB software ( v.17). Cu-Aln/GO hybrid exhibits the maximum qe ( 1005 +/- 2.3 mu mol/g) at the L7 test (pH: 10, dose 1 g/ L, and Temp. 323 K). While Cu-Aln/GO@Alg at L5 test at pH 7, dose: 2 g/L, and Temp. 323 K shows the maximum qe of 1200 +/- 9.4 mu mol/g. Moreover, Cu-Aln/GO@Alg heterostructure enhances removal efficiency (qe. 1400 +/- 1.4 mu mol/g) more than Cu-Aln/GO (qe. 990 +/- 0.54 mu mol/g) in saline water (total dissolved solids (TDS). 30,000 ppm) due to the influence of the salting-out effect. Furthermore, the evaluation of the adsorption performance of TOPs along with their adsorption mechanism was properly determined using three-parameter nonlinear models (Langmuir-Freundlich [L- F] and Redlich-Peterson [R-P]) with the best fit -(R2 -1) than the nonlinear two-parameter models (Langmuir [L] and Freundlich [F]). The Cu-Aln/GO@Alg hydrogel showed high adsorption capacity of TOPs reached 2840.30 mu mol/g, 2911.67 mu mol/g, 2940.23 mu mol/g for Ph, 2-CP, and 2,4 DCP, respectively. The hydrogel exhibited multilayer adsorption of the TOPs (g = 1.92). Furthermore, the L-F model's heterogeneity constant value (m 0 and m. 1) indicated different adsorption sites with varying energies at the surface. The reusability of Cu-Aln/GO@Alg composite was determined up to four reusable cycles.