The present study was focused on the removal of methylene blue (MB) from aqueous solution by ultrasound-assisted adsorption onto the gold nanoparticles loaded on activated carbon (Au-NP-AC). This nanomaterial was characterized using different techniques such as SEM, XRD, and BET. The effects of variables such as pH, initial dye concentration, adsorbent dosage (g), temperature and sonication time (min) on MB removal were studied and using central composite design (CCD) and the optimum experimental conditions were found with desirability function (DF) combined response surface methodology (RSM). Fitting the experimental equilibrium data to various isotherm models such as Langmuir, Freundlich, Tempkin and Dubinin-Radushkevich models show the suitability and applicability of the Langmuir model. Analysis of experimental adsorption data to various kinetic models such as pseudo-first and second order, Elovich and intraparticle diffusion models show the applicability of the second-order equation model. The small amount of proposed adsorbent (0.01 g) is applicable for successful removal of MB (RE>95%) in short time (1.6 min) with high adsorption capacity (104-185 mg g(-1)).

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The present study focused on the simultaneous ultrasound-assisted removal of sunset yellow and erythrosine dyes from aqueous solutions using ZnS:Ni nanoparticles loaded on activated carbon (ZnS:Ni-NP-AC) as an adsorbent. ZnS:Ni nanoparticles were synthesized and characterized using different techniques such as FESEM, XRD and TEM. The effects of various parameters such as sonication time, pH, initial dye concentrations and adsorbent dose on the percentage of dye removal were investigated. Parameters were optimized by central composite design (CCD) combined with response surface methodology (RSM) and desirability function (DF). A good agreement between experimental and predicted values was observed. The ultrasound-assisted adsorbent (0.04 g) was capable of high percentage removal (98.7% and 99.6%) of sunset yellow and erythrosine in short time (3.8 min).

The present study investigates the simultaneous ultrasound-assisted adsorption of malachite green (MG) and safranin O (SO) dyes from aqueous solutions by ultrasound-assisted adsorption onto copper nanowires loaded on activated carbon (Cu-NWs-AC). In this study a novel and green approach described for the synthesis of Cu nanowires. This novel material was characterized using different techniques such as FESEM, XRD, EDS and UV-Vis. The effects of variables such as sonication time, pH, adsorbent dosage and initial dyes concentrations on the simultaneous dyes removal were studied and optimized by a central composite design (CCD) combined with desirability function (DF). A good agreement between experimental and predicted data using optimal model in this study was observed. These results indicate that a small amount of proposed adsorbent (0.022 g) was applied for simultaneous removal of 15 mg L -1 of malachite green and 15 mg L -1 of safranin O (>99%) in a short time (6.0 min) and pH of 5.5.