Brilliant green dye adsorption from aquatic medium using an activated carbon/graphene/polyacryl amide composite as a novel effective adsorbent: experimental investigation and factorial design optimization

Abstract

The rising levels of synthetic dyes in water bodies pose significant environmental challenges due to their resistance to traditional treatment methods, chemical stability and toxicity. Recent research has focused on the development of an innovative composite material, AC/G/PAA, which combines activated carbon (AC), graphene (G) and polyacrylamide (PAA) to enhance the removal of Brilliant Green Dye (BGD). The unique properties of the functional groups in AC, combined with the characteristics of graphene and PAA, significantly enhance the adsorption capabilities of the composite. Comprehensive characterization through FTIR and SEM confirmed the successful synthesis and favorable surface properties of the AC/G/PAA composite. A Central Composite Design (CCD) model was employed to probe the influence of four independent variables on adsorption efficiency. These variables included the initial concentration, which varied from 1 to 30 mg L⁻¹, contact time ranging from 10 to 50 minutes, pH levels between 3 and 8, and adsorbent dosage that spanned from 100 to 600 mg. The analysis of residual plots indicated that the model assumptions of normality, constant variance, and independence were adequately met, reinforcing the validity of the regression analysis. The equilibrium studies adhered to the Langmuir isotherm model, revealing a maximum adsorption capacity of 105.2 mg g⁻¹, indicative of monolayer adsorption that exceeds many previously reported composites for BGD removal. Kinetic studies suggested that the adsorption is consistent with the pseudo-second-order kinetics, signifying a significant chemisorption mechanism. Furthermore, the AC/G/PAA composite exhibited remarkable reusability for the removal of BGD over four successive cycles, highlighting its potential as an effective, economical, and biodegradable sorbent for sustainable water treatment applications.