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The understanding of mechanistic insights in environmental remediation and mitigation systems is attracting larger attention, in recent days. Here in, aluminium substituted copper ferrite impregnated rGO hybrid (CAF-rGO) is verified to understand the adsorption/electrosorption mechanism of arsenic in aqueous systems. Near-surface study (XPS: As 3d, Cu 2p, Fe 2p, Al 2p, O 1s, C 1s) proposes redox, and ligand exchange reactions between contaminant, and CAF-rGO. Adsorption capacities are observed around 128.8 mg g−1 [As(III)], 153.5 mg g−1 [As(V)] with Freundlich model isotherms. Kinetics study follows the PSO model with influence of solar light (> 420 nm). Cyclic voltammetry (CV) analysis in different molarity conditions observed with signals around +0.1 and −0.6 V confirm the redox abilities, and N 2 /O 2 purged environments understood that electrosorption occurred through both reduction and sorption. Electrosorption study with pH variation shows the effect of protonation on the redox activity of individual arsenic species. Consistent signal around −0.6 ± 0.05 V in all the CV plots (i.e., Molarity, Environment, pH) recommends the usage of CAF-rGO for arsenic mitigation. Possible influence of photo-current (∼40 μA/cm2 at ∼ 0 V) towards As(III/V) decontamination is understood though photoelectrochemical analysis. Impedance plot shows low-resistance and better diffusion of arsenic oxy-anions during light irradiation. Synergistic nature of CAF-rGO generates reactive oxygen species (i.e., ●OH/●O 2 −/ 1 O2) in mitigating highly toxic As(III) species is also detailed in the present work. Image 1 • Mechanistic insights of arsenic (As) adsorption and electrosorption in aqueous systems. • In-situ CV analysis in various molarities, gas purging environment and pH conditions. • A constructive correlation is drawn between individual redox signals and CV plot areas. • Photo-catalytic aspects on As loading and photo-electrochemical behavior (I vs. t, EIS). • ROS signals onto the hybrid surface in influencing As remediation and mitigation. [ABSTRACT FROM AUTHOR]

• MAF-rGO hybrid is verified for better arsenic (As) remediation under visible light (λ > 420 nm). • Photo-catalytic/electrocatalytic synergised MAF-rGO: High photocurrent density (0.9 mA cm−2). • XPS analysis confirmed the occurrence of redox reactions and ligand exchange phenomenon. • CV studies provide the mechanism of electro-sorption through reduction and sorption. • Sustainable use of sludge as ultra-high stable supercapacitor electrode (~100,000 cycles). Synergistic Mn-Al-Fe impregnated rGO hybrid (MAF-rGO) is developed and verified for arsenic remediation. Preliminary adsorption studies are observed through vibrational spectroscopy and morphological tools. Adsorption isotherms are fitted by Freundlich model multilayer sorption with a loading of 402 mg g−1 [As(III)], and 339 mg g−1 [As(V)]. Adsorption kinetics study in competing ion environment [SO 4 2−, PO 4 3−, NO 3 −, CO 3 2−] confirms the PSO model-controlled chemisorption as the rate-limiting step. The irradiation of white light (> 420 nm) in adsorption kinetics study shows a two-fold increase in the arsenic loading parameters (5–10 min). Multiplet peaks in As3d spectra (XPS) confirm the transformation of arsenic species in the near-surface region of hybrid [i.e., As(III), As(V)]. The occurrence of redox-active, ligand-exchange reactions are confirmed by individual Mn2p, Fe2p, Al2p, O1s, and C1s spectra. The dedicated electrochemical study confirms arsenic decontamination occurred through both reduction and sorption (i.e., electrosorption). An energy bandgap (E g) of 2.17 eV resulted in the photocatalytic activity, which enhanced the arsenic remediation. Photo-electrocatalytic synergism resulted in high photocurrent densities (0.2–0.9 mA cm−2) with charge separation [e−–h+], and built-in potential abilities (Schottky-junction; Water-splitting). Arsenic-treated hybrid (i.e., sludge) is observed with an ultra-high stable charge–discharge cyclic performance for 100,000 cycles (~77 %) with improved specific-capacity of 125 F g−1 over pristine hybrid (92 F g−1). The better electrochemical parameters of sludge are due to the efficient lithiation/de-lithiation process supported by adsorbed arsenic. This work proposes sustainable approach towards environmental remediation and energy storage applications. [ABSTRACT FROM AUTHOR]