The Adsorption Characteristics Of Organic-vermiculite And Organo-silica Nanosheets Modified By Functional Gemini Surfactant

Gemini-based organo-clays is a low-cost and effective adsorbent for the remediation of micropollutants.The additional interactions play important roles during adsorption.It is environmentally significant to develop and design the novel gemini-based organo-clays as adsorbent.In this work,benzene-and amide-containing gemini surfactants with different alkyl chain lengths(PAC12/14/16)and dipyridyl-containing gemini surfactant(DHBP)were synthesized and acted as modifiers to prepare organo-vermiculites(PAC12/14/16-Vt)and organo-silica nanosheets(DHBP-Si NSs).Key characteristic analyses of resultant adsorbents were characterized by Fourier transformed infrared spectroscopy(FT-IR),elemental analysis(EA),X-ray diffraction(XRD),thermogravimetric analysis(TG)scanning electron microscope(SEM)and surface areas analysis(BET).Sulfamethoxazole(SMX),clofibric acid(CA),ketoprofen(KP)and naproxen sodium(NPX)were chosen as models for the adsorption properties and mechanisms of the resultants.The characterization results of PAC12/14/16-Vt suggested the saturated surfactants dosage was 0.4 CEC.The inserted surfactants adopted the coexistence of paraffin-type bilayer and monolayer arrangement in the interlamination.The characterization results of DHBP-Si NSs indicated the saturated surfactants dosage was 0.84 mmol.The most of modifier intercalated in the interlayer space through physical adsorption and adopted a coexistence of paraffin-type monolayer and pseudotrimolecular interlayer arrangement.The adsorption of SMX onto organo-vermiculites was in the order of PAC14-Vt(72.79 mg/g)> PAC12-Vt(63.47 mg/g)≈ PAC16-Vt(62.97 mg/g).This can be reasonably attributed to suitable interlayer packing density and strong additional interactions.The strength of combination of hydrogen bond and NH-π interaction was stronger than π-π interaction during adsorption process.The adsorption of SMX onto PAC12/14/16-Vt was matched pseudo-second-order and Freundlich isotherm models,a spontaneous and exothermic process in nature.DHBP-Si NSs showed remarkable adsorption capacities of clofibric acid(CA;216.59 mg/g),ketoprofen(KP;326.36 mg/g)and naproxen sodium(NPX;260.57 mg/g).The adsorption of NPX was controlled by π-π interaction,however,partition and π-πstacking played important roles during the removal of KP.Multiple interactions were involved in the elimination of CA.The adsorption of CA and KP were in agreement with Freundlich isotherm model,while Langmuir model held for the retention of NPX.The adsorption was agreed well with pseudo-second-order model and a spontaneous and exothermic process.The strength of interactions during adsorption:(i)π-π interaction:pyridine/naphthalene > pyridine/benzene > pyridine/orthogonally benzene,(ii)π-πstacking: orthogonally benzene > benzene > naphthalene,(iii)π-π interaction between pyridine/naphthalene > the synergy of OH-π interaction between hydroxyl/pyridine andπ-π interaction between pyridine/benzene..