Ultrahydrophobic melamine sponge via interfacial modification with reduced graphene oxide/titanium dioxide nanocomposite and polydimethylsiloxane for oily wastewater treatment

Three-dimensional(3D)porous absorbents have attracted significant attention in the oily wastewater treatment technology due to their high porosity and elasticity.Given their amphiphilic surface,they have a propensity to simultaneously absorb water and oil,which restricts their range of applications.In this study,a reduced graphene oxide and titanium dioxide nanocomposite(rGO/TiO_(2))was used to fabricate an ultra-hydrophobic melamine sponge(MS)through interfacial modification using a solution immersion technique.To further modify it,poly-dimethylsiloxane(PDMS)was grafted onto its surface to establish stronger covalent bonds with the composite.The water contact angle of the sponge(rGO/TiO_(2)/PDMS/MS)was 164.2°,which satisfies the condition for ultrahydrophobicity.The evidence of its water repellency was demonstrated by the Cassie-Baxter theory and the lotus leaf effect.As a result of the increased density of rGO/TiO_(2)/PDMS/MS,it recorded an initial capacity that was 2 g/g lower than the raw MS for crude oil absorption.The raw MS retained 53% of its initial absorption capacity after 20 cycles of absorption,while rGO/TiO_(2)/PDMS/MS retained 97%,suggesting good recyclability.Excellent oil and organic solvent recovery(90%-96%)was demonstrated by rGO/TiO_(2)/PDMS/MS in oil-water combinations.In a continuous separation system,it achieved a remarkable separation efficiency of 2.4×10^(6)L/(m^(3)·h),and in turbulent emulsion separation,it achieved a demulsification efficiency of 90%-91%.This study provides a practical substitute for massive oil spill cleaning.

A comparative study of adsorption behavior of rifampicin,streptomycin,and ibuprofen contaminants from aqueous solutions onto chitosan:Dynamic interactions,kinetics,diffusions,and mechanisms

Adsorptive removal and dynamic interaction of three different pharmaceutical pollutants,namely rifampicin(RIF),streptomycin(STM),and ibuprofen(IBU)onto chitosan were systematically investigated using a batch adsorption technique at different processing parameters.In this study,chitosan was derived from mud-crab shells,as an innovative way to use the waste from marine foods as adsorbents.The kinetics,intraparticle diffusion,mechanism,and thermodynamics of the adsorption were systematically evaluated and analyzed using kinetic models,Boyd mass transfer and WebereMorris intraparticle diffusion models,Langmuir,Freundlich,DubinineRadushkevich,and Temkin isotherm models,and the Gibbs equation.The adsorption isotherm of the larger molecules,RIF and STM,could be explained by the Langmuir isotherm model,in contrast,that of IBU,which is a much smaller molecule,followed the Freundlich isotherm model.The maximum adsorption capacity of RIF,STM,and IBU on chitosan was estimated to be 66.91 mg g^(-1),11.00 mg g^(-1),and 24.21 mg g^(-1),respectively,which are higher compared to those on a variety of agricultural wastes,suggesting that this biopolymer is a potential practical and economical adsorbent to remove the pharmaceutical compounds from wastewater.The adsorption mechanism of the pharmaceutical compounds on chitosan is proposed based on the vibrational spectroscopic analyses,XRD patterns,and DSC thermograms of the biopolymer before and after adsorption process.