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This study involves the production of a novel biosorbent obtained from Cortaderia selloana flower spikes (CSFs). Magnetic C. selloana flower spikes (nM∞CSFs) was applied as an ideal biosorbent for ...

PAN nanofiber-Mat (n-fib@Mat), PAN/ZnO n-fib@Mat, and PAN/ZnO-TiO2 n-fib@Mat were prepared via electrospinning method. Their high adsorption capacities against dissolved Cr (VI) ions make them as super adsorbents for water treatment. The structure of n-fib@Mat was investigated using XRD, FTIR, SEM, and TEM techniques. The effects of selected parameters such as contact time, initial concentration, and n-fib@Mat amount were assessed in a fixed bed reactor. It was found that the adsorption capacities of PAN n-fib@Mat, PAN/ZnO n-fib@Mat, and PAN/ZnO-TiO2 n-fib@Mat were pH-dependent and the optimal pH value was between 2.1 and 2.2. The adsorption was rapid, and the equilibrium was reached within 240 min to remove of Cr (VI) ions for PAN/ZnO-TiO2 n-fib@Mat and 360 min for PAN n-fib@Mat and PAN-ZnO n-fib@Mat. Langmuir isotherms model is preferred for PAN n-fib@Mat, PAN-ZnO n-fib@Mat, and PAN/ZnO-TiO2 n-fib@Mat for Cr (VI) adsorption. The equilibrium adsorption capacities are 153.85 mg/g, 234.52 mg/g, and 333.43 mg/g for PAN n-fib@Mat, PAN/ZnO n-fib@Mat, and PAN/ZnO-TiO2 n-fib@Mat for Cr (VI), respectively. The produced n-fib@Mat showed excellent removal ability for Cr (VI). The adsorption kinetic was obeyed pseudo-second-order reaction rate.

Polymer nanofibers are valuable materials that are of great importance because they are inexpensive and they display high strength. In this study, nylon-6,6 (N6,6)/graphene oxide (GO) nanofibers were developed and characterized. GO was synthesized from graphene using the known Hummer’s method. GO is obtained by reaction of the graphene with strong oxidants and was characterized using Fourier-transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The characterizations showed that the graphene was suitably oxidized. GO was added to N6,6 to produce N6,6/GO nanofibers at loadings of 0.5, 1.0, 1.5, and 2.0 wt% through the melt mixing method. The batch adsorption model for Cr (VI) adsorption was applied as a function of time, initial Cr (VI) concentration, adsorbent dosage, and pH to examine nanofiber activity. N6,6/GO a exhibited high adsorption capacity for Cr (VI) at pH 2.0. The maximum adsorption capacity for Cr (VI) ion was found to be 47.17 mg/g of N6.6/GO using the related isotherm curves and equations. When the equilibrium data were examined, it was concluded that Langmuir adsorption isotherm was more suitable.

This study evaluates the application of Cr(VI) adsorption from the prepared synthetic solution by black sesame (Sesamum indicum L.) seed pulp (BSSP) and chitosan (Cts)-coated black sesame seed pulp beads (Cts-BSSP). BSSP and Cts-BSSP were used as an adsorbent without any chemical or physical treatment to remove Cr(VI) from an aqueous medium. The results indicated that the Cr(VI) removal was pH-dependent and reached an optimum at pH 2.0. It has been observed that the percentage of adsorption increased from 62% to 95% when the amount of Cts-BSSP increased from 0.0125 g to 0.0250 g. The required adsorbent amount for the maximum removal was 0.05 g and 0.1 g for Cst-BSSP and BSSP, respectively. The contact time for the adsorption was 120 min and 90 min for BSSP and Cst-BSSP, respectively. Scanning electron microscopy and Fourier transform infrared spectroscopy were used to explore the possible adsorption mechanism for Cr(VI). The equilibrium data for the BSSP and Cts-BSSP were used with the Langmuir and Freundlich adsorption isotherm models to assess the adsorption capacity and relevant mechanism. The adsorption capacity of the Cts-BSSP for Cr(VI) is relatively high compared to BSSP. The monolayer maximum adsorption capacities for Cr(VI) ions were 31.44 and 18.32 mg/g for Cts-BSSP and BSSP, respectively.

The forms of utility in the wastewater treatment of chitosan-based adsorbents acquired from natural substances have attracted numerous attentions in recent years. The use of chitosan modified adsorbents for removal of the chromium has aroused great interest. When chitosan-based modified adsorbents are considered, they have got large amount of an amino (-NH2) and hydroxyl (-OH) functional groups. Such adsorbents display that they have high activity and therefore they may be extensively utilized in wastewater treatment plants to cast off chromium. In this chapter, the utility outcomes of chitosan-based substances will be explained after applying different parameters to remove Cr (VI) from the aqueous surrounding with the information obtained the use of batch adsorption systems. Application of various chitosan-based adsorbents for Cr (VI) removal application will be demonstrated in a detailed way and they will be discussed within the textual content.

Citric acid treated peach (Prunus persica) stone shell as an effective adsorbent were synthesized for the adsorption of Cr (VI) from aqueous solutions. The aim of this study was to predict the optimal conditions for citric acid modification of peach kernel shell (CA-PSS) the modification process and the removal of Cr (VI) ions from aqueous solutions using a batch-type model. Research of its adsorption of Cr (VI) showed that CA-PSS in conditions at 120 °C for 4 h and in mass ratio of peach stone shell: citric acid =1:1 had greater adsorption capacity. Cr (VI) adsorption was investigated by changing several conditions. Adsorption studies have been carried out to determine the effect of time, pH, adsorbent dosage, temperature, and initial Cr (VI) ions concentration on the adsorption capacity of Cr (VI) ions by the esterified peach stone shell. The results indicate that the Langmuir model provides a better fit for the adsorption data. The equilibrium adsorption capacity of Cr (VI) was 25.71 mg/g for CA-PSS. The adsorption kinetic process followed the pseudo-second-order kinetics. Thermodynamic parameters such as the changes in ΔG°, ΔH°, and ΔS° have also been estimated, and the process was found to be spontaneous.

This study investigates the adsorption of Cu(II) and Pb(II) ions onto magnetic-plum stone activated carbon (m-PSAC). Plum stone-activated carbon (PSAC) was produced by chemical activation of plum stone (PS) with phosphoric acid (H3PO4) in N2 inert atmosphere. The effects of activator ratio, activation temperature, and impregnation temperature were examined. m-PSAC was prepared by co-precipitation method which is a combination of PSAC with Fe2 +:Fe3 + salts. The prepared m-PSAC was characterized by scanning electron microscopy (SEM) and Fourier Transform infrared spectrophotometer (FT-IR). Then m-PSAC was used for the removal of Cu(II) and Pb(II) ions from aqueous solutions. The effects of initial pH, the amount of m-PSAC, temperature, contact time, and the initial concentration of Cu(II) and Pb(II) were investigated during the equilibrium and kinetics studies. Adsorption isotherms for the Cu(II) and Pb(II) on m-PSAC was determined and correlated with Langmuir, Freundlich, Scatchard and D-R isotherm equations. The adsorption data showed that adsorption of Cu(II) and Pb(II) was fitted by Langmuir isotherm model and pseudo-second-order kinetics model. Under the optimized conditions, maximum adsorption capacities of Cu(II) and Pb(II) ions determined by Langmuir model were enhanced 48.31 and 80.65 mg/g, respectively. Thermodynamic parameters such as ΔG°, ΔH°, ΔS°, Ea were calculated and the interaction of metals with m-PSAC was found to be exothermic and spontaneous in nature.

A novel chitosan-humic acid-graphene oxide (Cts-HA-GO) composite was produced and tested to remove hexavalent chromium (Cr(VI)) during the adsorption process. The percentage adsorption was 85.28% by using 200 ppm Cr(VI) and 2 g/L composite. Four hours of contact time was enough to remove Cr(VI) from the aquatic medium. The extent of adsorption of Cr(VI) on the surface of Cts-HA-GO composite was examined on the basis of increasing quantity of the composite. The functional group characterization and morphology of composite was characterized using scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy. After reaching the equilibrium, the residual concentration of the Cr(VI) solution was measured with an UV-visible spectrophotometer. The results showed that the adsorption behaviour was in accordance with the Langmuir isotherm model, and the maximum adsorption capacity of Cr(VI) determined by using this model was 83.64 mg/g at the pH of 2. A pseudo-second-order model equation has justified the equilibrium between Cr(VI) and the composite for the kinetic studies.

Environmental pollution has been increasing recently due to industrialization. Many industries use dyestuffs to color their products. This work investigates the adsorption of methylene blue (MB), malachite green (MG), and methyl violet (MV) on alginate-coated perlite beads (AP). AP was prepared by a sol-gel process. The removal of MB, MG, and MV from aqueous solutions by AP as an adsorbent was tested by using a batch-type model. In order to prove the effectiveness of the study, it has been tried to obtain optimum efficiency at optimum level by working depending on mixing time (minutes), initial dye concentration (ppm), adsorbent dose (mg/L), pH, and temperature (°C). The results showed that the MB, MG, and MV adsorption process reached equilibrium within a 60-min period for AP. It has been found that the amount of adsorbed dyestuff increases with the initial dye concentration, the pH of the solution. Thermodynamic activation parameters were calculated from experimental data at different temperatures. The AP was characterized by Fourier Transform Infrared Spectroscopy (FT-IR) before and after MB, MG, and MV adsorption. The equilibrium adsorption data were described by Langmuir, Freundlich, Scatchard, Temkin and D-R isotherms. The modified Langmuir isotherm was applied to explain the experimental adsorption, and the greatest MB, MG, and MV adsorption capacity of the AP reached to 104.1, 74.6, and 149.2 mg/g, respectively. The pseudo-first and pseudo-second-order equations were used to evaluate the kinetic data, and the constants are determined. The best correlation coefficients were well described using the pseudo-second-order kinetic model. As a result, AP has claimed the possibility as an adsorbent for MB, MG, and MV removal from dilute aqueous solutions.

The adsorption of Cr(VI) on rye husk (RH) was studied at varying Cr(VI) concentrations, adsorbent dose, contact time, and pH. Maximum Cr(VI) was sequestered from the solution within 140 min and the maximum removal of 5.0 mM Cr(VI) was about 68% at pH of 3.0 for 0.5 g RH. The removal of Cr(VI) was maximum (80.0%) when the initial pH of the solution was kept at 3.0. The Cr(VI) adsorption capacity of RH samples was calculated as 0.435 mmol/g at pH 3.0 from Langmuir isotherm. The adsorption kinetics data were evaluated with first-order reversible and pseudo-second-order kinetics models.

Polyacrylonitrile/titanium dioxide nanofiber (PAN/T-nF) membrane was prepared with TiO2 nanoparticles which dispersed into polyacrylonitrile (PAN) matrix with ultrasonic probe in ultrasonic bath. The amount of TiO2 loaded in the membrane was 1 and 3 wt% to explore the activity of membranes in the adsorption process. PAN/T-nF membrane was prepared by electrospinning technique. The potential of the prepared PAN/T-nF membrane was investigated for the removal of Cr(VI) from aqueous solutions. The adsorption equilibrium was investigated in the batch process. The adsorption process displayed pH dependence and the maximum Cr(VI) adsorption took place at pH 2. The equilibrium was attained at a contact time of 180 min and Langmuir adsorption model was suitable for the adsorption isotherms. Maximum adsorption capacities 245.3 and 280.4 mg Cr(VI)/g were calculated for 1 and 3% PAN/T-nF membrane, respectively. The adsorption of Cr(VI) on PAN/T-nF was related to the mechanism of surface complexation, coordinat...

Barley straw (BS), a very low-cost material, has been utilized as a biosorbent material for the removal of copper (Cu 2+ ) ions from aqueous solutions after treatment with citric acid. Barley straw was thermochemically modified with citric acid (CA–BS) for the purpose of improving the Cu 2+ ion sorption capacity of the straw. Biosorption studies have been carried out to determine the effect of pH, adsorbent concentration, contact time, extent of modification, and adsorbate concentration on the biosorption capacity of Cu 2+ ions by the esterified straw. The equilibrium sorption capacities of Cu 2+ were 4.64 mg/g and 31.71 mg/g for BS and CA–BS, respectively. The optimum pH for the removal of Cu 2+ ions by CA–BS was around pH 7.0 and the removal of Cu 2+ ions was 88.1%. Langmuir, Freundlich, Scatchard and D–R (Dubinin–Radushkevich) isotherms have been used to characterize the observed biosorption phenomena of Cu 2+ ions on CA–BS. The carboxyl groups on the surface of the modified barley straw were primarily responsible for the sorption of Cu 2+ ions.

The biosorption of Cr(VI) by the garlic stem (GS)-Allium sativum L. and horse chesnut shell (HCS)-Aesculus hippocastanum plant residues in a batch type reactor was studied in detail for the purpose of wastewater treatment. The influence of initial Cr(VI) concentration, time, and pH was investigated to optimize Cr(VI) removal from aqueous solutions and equilibrium isotherms and kinetic data. This influence was evaluated. The adsorption capacity of the GS and the HCS for Cr(VI) was determined with the Langmuir and Freundlich isotherm models, and the data was fitted to the Langmuir. The adsorption capacity of the GS and the HCS was found to be 103.09 and 142.85 mg/g of adsorbent from a solution containing 3000 ppm of Cr(VI), respectively. The GS's capacity was considerably lower than that of the HCS in its natural form. Gibbs free energy was spontaneous for all interactions, and the adsorption process exhibited exothermic enthalpy values. The HCS was shown to be a promising biosorbent for Cr(VI) removal from aqueous solutions.

WOS: 000219332000003, The powdered activated carbon (AC) supported by carbonaceous nano-adsorbents were examined to remove hexavalent chromium [Cr(VI)] from aqueous solution The adsorption behaviour of micro-level concentration of Cr(VI) on those nano-adsorbents was investigated as a function of the experimental conditions such as the contact time, the pH, the dosage of adsorbent, and the initial concentration of Cr(VI). The structural characterization of the adsorbents was accomplished by Fourier transform infrared spectroscopy and scanning electron microscopy. Adsorption isotherms including Freundlich and Langmuir have been applied to study the equilibrium of the adsorption behaviour and identify the adsorption capacity of the activated carbon-functionalized multiwalled carbon nanotubes (AC/f-MWCNTs) and activated carbon-functionalized carbon nanospheres (AC/f-CNSs). Langmuir isotherm model showed that the adsorption process was monolayer type under working with an adsorption capacity of 113.29 and 105.48 mg/g, respectively, for AC/f-MWCNTs and (AC/f-CNSs)., TUBA (Turkish Academia of Sciences); Selcuk University, BAPSelcuk University [14101008], The authors thank TUBA (Turkish Academia of Sciences) and Selcuk University, BAP (Project number-14101008) for the financial support.