Order Kinetic Equation Research Articles

Design and fabrication of core-shell magnetic and non-magnetic supported carbonaceous metal organic framework nanocomposites for adsorption of dye

A novel core-shell cobalt and nickel based metal organic framework (MOF) nano-composites in the presence of the magnetic and non-magnetic walnut based activated carbon (AC) were subsequently employed for the adsorption of methylene blue (MB) in the batch system which were synthesized by an efficient and a facile preparation method. The nano-composites were characterized by applying general tests including XRD, FTIR, FESEM, EDX, TEM, VSM, TGA and BET. The findings indicated that the nanoparticle size of the well dispersed magnetic nano-composites was less than 20 nm. The core-shell structure of magnetic nanocomposites was detected from TEM images. The analytical achievements also demonstrated that the thermal resistance of the magnetic composites was higher than that of other samples. The maximum adsorption capacities were calculated to be 128 and 112.32 mg/g for the cobalt based MOF supported on the non-magnetic and magnetic ACs, respectively which was higher compared with the nickel based composites. Langmuir isotherm and a pseudo second order kinetic equation were fit models to describe the equilibrium adsorption and the kinetic behavior of MB on the adsorbents, respectively. The usability of the prepared samples was also studied for six cycles which showed the acceptable performance of the magnetic adsorbents for the real applications.

Preparation of MIL-100 via a novel water-based heatless synthesis technique for the effective remediation of phenoxyacetic acid-based pesticide

An iron-based metal-organic framework (MOF), MIL-100(Fe) has been synthesized by a novel water-based heatless recipe. The physical-chemical qualities of MIL-100(Fe) were examined by X-ray diffraction, Field Emission Scanning Electron Microscopy, Nitrogen adsorption-desorption isotherm, Thermogravimetric Analysis and Fourier Transform Infrared Spectroscopy. With a high specific surface area of 1,893 m2/g, the crystalline MIL-100(Fe) exhibited an extraordinary performance for the adsorptive removal of 2,4-dichlorophenoxyacetic acid (2,4-D) pesticide from the aqueous solution under laboratory and on-site conditions. The adsorption equilibria have been simulated by the nonlinear Langmuir, Freundlich, Sips, Dubinin–Radushkevich, and Redlich–Peterson isotherm models, with a monolayer adsorption capacity for 2,4-D of 858 mg/g. The adsorption kinetics was rapid, with exceeding 50% of the adsorbate loading has been completed within the first 5 min of contact time, and best described by the pseudo-second order kinetic equation. Further analyses with the Bangham, Vermeulen, and intraparticle diffusion models concluded that intraparticle pore diffusion is the controlling mechanism, but it is not the sole rate-limiting step. MIL-100(Fe) retained the adsorptive performance in the 2,4-D loaded tap water and lakewater samples. The profound effects with solution pH and ionic strength on the adsorptive uptake suggested that the prevailing interaction was the electrostatic attraction between the deprotonated 2,4-D and positive-charged MIL-100(Fe). The adsorption process was spontaneous with favorable enthalpy and entropy changes as the thermodynamic driving force. Water stability test illustrated negligible iron leaching from the Fe-MOF. MIL-100(Fe) adsorbent could be reused for at least 5 times, with minor deterioration in the adsorptive uptake via simple solvent stripping. The high adsorptive potential and well-developed porosity, supported by the sustainable preparation methodology, rendered MIL-100(Fe) a promising adsorbent for the effective decontamination of water pollutants.

Physicochemical properties and lead ion adsorption of biochar prepared from Turkish gall residue at different pyrolysis temperatures.

How to correctly and scientifically dispose of medicine residue on the basis of protecting the environment is an urgent problem to be solved due to the continuous generation of a large amount of waste medicine residue. In this paper, the application of waste medicine residue (large volume produced each year) as a precursor in producing a biochar that could adsorb Pb ion was reported. Biochar is a stable, aromatic, porous substance that is rich in carbon and prepared through pyrolysis of waste biomass under anaerobic conditions. In this study, medicine residue was used as raw material, and high-temperature sintering furnace was used to prepare medicine slag biochar at different temperatures of 200°C, 300°C, 400°C, 500°C, and 600°C. The resulting biochar was characterized by elemental analysis, Fourier transform infrared spectroscopy (FTIR), specific surface area analysis, field emission-scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and Raman spectroscopy (RS). Experimental results showed that with the increase in pyrolysis temperature, the biochar structure was destroyed. The yield decreased as the temperature gradually decreased from 81.69% to 33.90%. With the increase in temperature, the pH, the ash, and the fixed carbon gradually increased, whereas the number of surface functional groups decreased. The quasi second order kinetic equation can better fit the kinetic characteristics of adsorbing Pb ion by biochar. In general, this study provides a valuable method for recycling medicine residue.

A characteristic study of Zea mays L. (sweet corn) cobs for synthetic dye degradation from aqueous media.

The current study reports a systematic methodology of Zea mays L. (sweet corn) cobs (ZMLC) for the sequestration of synthetic dye (gentian violet) from aqueous solutions. Adsorbent was scrutinized by using scanning electron microscopy, Fourier transform infra-red spectrometry with pHpzc determination. The impact of various adsorption parameters including pH effect, ZMLC (sorbent) dosage, temperature, concentration and shaking time was examined. The equilibrium sorption isotherms were determined by the batch method from 283 to 303 K at pHpzc. Adsorption data were adjusted to four isothermal models: Langmuir, Freundlich, Dubinin-Radushkevich and Temkin's models, which presented the best adjustment to Freundlich, Dubinin-Radushkevich and Temkin's at 283 K. The kinetic profile fitted well to the pseudo-second order kinetic equation at three distinct concentrations 600, 700, 800 mg/L. Maximum sorption capacity was gained up to 700 mg.g-1 for gentian violet at pH 3, respectively. The adsorption process is endothermic, non-spontaneous, favorable thermodynamically due to positive values of entropy and Gibbs free energy and randomness decreases during the adsorption process. Furthermore, after biosorption onto ZMLC the dye can be desorbed effectively by using mineral base KOH solution. Consequently, the ZMLC is said to be a promising biosorbent to remediate gentian violet-contaminated water as well as wastewater.

Preparation of novel chitosan polymeric nanocomposite as an efficient material for the removal of Acid Blue 25 from aqueous environment

A novel, sustainable chitosan polymeric nanocomposite (CS-PVA@CuO) was synthesized and subjected to the removal of acid blue 25 (AB25) from the aqueous environment. The influence of different variables such as pH, contact time, initial dye concentration, temperature, and adsorption kinetics has been examined in the batch adsorption process. The CS-PVA@CuO composite was systematically characterized by XRD, FTIR, SEM, and EDX analysis. The pseudo-first order (PFO), pseudo-second order (PSO), and intra-particle diffusion kinetics equations were used to examine the kinetic data of the adsorption process. The adsorption kinetics confirms that the PSO model was a more exact fit. Thermodynamics study typically revealed that the uptake of AB25 by the adsorbent is spontaneous and endothermic in nature. Remarkably, the results reveal the highest adsorption capacity of the CS-PVA@CuO was 171.4 mg/g at 313 K. To be specific, CS-PVA@CuO polymer nanocomposite can be effectively used as a suitable adsorbent material for the potential elimination of anionic AB25 dye from the aqueous solutions.

One step acid activation of bentonite derived adsorbent for the effective remediation of the new generation of industrial pesticides

Herein, the facile one step acid activation of bentonite derived functionalized adsorbent (AB) for the effective remediation of both ionic and non-ionic secondary pesticides, ametryn and metolachlor has been attempted. The surface characteristics of AB were examined by the nitrogen adsorption–desorption analysis, scanning electron microscopy (SEM), and Fourier Transforms Infrared (FTIR) Spectroscopy. The adsorptive behavior was evaluated with respect to the effect of contact time, initial concentrations and solution pH. The equilibrium data were fitted to the Langmuir, Freundlich and Temkin isotherm models, while the adsorption kinetic was analyzed using the pseudo-first order and pseudo-second order kinetic equations. Thermodynamic parameters including the standard enthalpy change (ΔH°), standard entropy change (ΔS°), and Gibbs free energy change (ΔG°) were established. Thermodynamic analysis illustrated that the adsorption process was feasible and exothermic in nature, while the characterization findings verified the alteration of FTIR bands, and a high specific surface area of 464.92 m2/g, with a series of pores distributed over the surface. Equilibrium data was best confronted to the pseudo-second order kinetic model, while the adsorptive removal of ametryn and metolachlor onto AB was satisfactory described by the Langmuir isotherm model, with the monolayer adsorption capacities for ametryn and metolachlor of 2.032 and 0.208 mmole/g respectively. The findings outlined the potential of the newly develop AB for the on-site treatment of pesticide polluted water.

Efficient moxifloxacin degradation by CoFe2O4 magnetic nanoparticles activated peroxymonosulfate: Kinetics, pathways and mechanisms

CoFe2O4 magnetic nanoparticles (CoFe2O4 MNPs) were used as heterogeneous catalysts to activate peroxymonosulfate (PMS) for moxifloxacin (MOX) removal in this study. The impacts of initial pH, PMS, catalyst dosage, coexisting ions, and natural organic matter (NOM) were investigated, and the possible degradation pathways of MOX were proposed. The results indicated that efficient degradation of MOX (99.8%) could be achieved in the CoFe2O4/PMS system with the optimum reaction condition (initial pH = 9, CoFe2O4 dosage = 100 mg/L, PMS dosage = 0.25 mM, reaction time = 30 min, and MOX concentration = 5 mg/L). The rule of MOX degradation followed the pseudo-first order kinetic reaction equation (kobs = 0.194 min−1). According to the results of radical scavenging experiments, the contribution of HO• on MOX removal was negligible, and SO4•− played a dominant role in MOX degradation. Five probable MOX degradation pathways were proposed based on the identified fifteen degradation intermediates, including defluorination, decarboxylation, decyclopropyl reaction, transformation of quinolone moieties, oxidation, and cleavage of nitrogen-containing heterocycle. The existence of 5 mM Cl-, HCO3−, and HA posed stronger negative effects on MOX removal. However, the MOX removal efficiency increased with H2PO4- concentration in the first 15 min. The removal efficiency of MOX decreased significantly in the CoFe2O4/PMS system when the catalyst was reused five times. These research conclusions could provide useful information for the practical application of CoFe2O4/PMS system in wastewater treatment of antibiotics.

The oxidation study of N,N-diethyl-meta-toluamide in dual frequency ultrasonic reactor

With the increasing concern of emerging contaminants (ECs), advanced oxidation processes (AOPs) have been widely investigated to fulfill the drinking water quality because of the potential adverse health effects of ECs. Accordingly, N,N-diethyl-meta-toluamide (DEET) is selected as a model compound belonging ECs to monitor its ultrasonic oxidation which is one of the most popular AOPs in a dual frequency ultrasonic reactor (DFUR) using low-frequency probe (20 KHz) and high-frequency transducer (640 KHz) type sources. DFUR was calorimetrically optimized in terms of power densities of both ultrasonic sources in order to provide the highest sonochemical yield with efficient energy output. Pseudo-first order kinetic equation was applied to results by measuring the concentration decreasing during the oxidation reactions. The pseudo-first-order rate constants, k, increased from 7.8x10-3 min-1 (640 kHz, R2=0.930) to 13.5x10-3 min-1 (DFUR, R2=0.990), by contrast, the rate constant was only 0.7x10-3 min-1 (R2=0.281) for 20 kHz low-frequency ultrasonic source. DEET oxidation was evaluated with the presence of different gas saturation (Ar, Air, O2, and N2); addition of hydrogen peroxide (PO), persulfate (PS) and monoperoxysulfate (MPS) and PO concentration effect (molar ratio of DEET:PO; 1:1, 1:2, 1:5, 1:10 and 1:20). The DEET oxidation rate was calculated as 35.8 x10-3 min-1 (R2=0.994) in the presence of Argon gas saturation, while it was 13.5 x10-3 min-1 (R2=0.990) when no gas bubbling. Therefore, the main degradation pathway was predicted as pyrolysis taking place inside the cavitation bubble where DEET molecules can reach. On the other side, a lower degradation rate in the presence of PO, PS, and MPS than that of no additives has indicated that the bulk phase degradation pathway for some part of DEET molecules are still occurred.

Hierarchical porous boron nitride with boron vacancies for improved adsorption performance to antibiotics

Designing atomically defective adsorbents with high specific surface area has emerged as a promising approach to improve sorption properties. Herein, hierarchical porous boron nitride nanosheets with boron vacancies (Bv-BNNSs) were in-situ synthesized via a one-step ZnCl2-assisted strategy. Being benefitted from the dual-functional template of zinc salt, highly-active boron vacancies and abundant hierarchical pores were simultaneously generated in the Bv-BNNSs framework. By employing the boron vacancies engineering strategy, the morphological and electronic structures were controllably tuned. Meanwhile, the specific surface area was improved to as high as 1104 m2/g. Owning to the abundance of accessible surface active-sites, the sorption capacity to antibiotic tetracycline (TC) on Bv-BNNSs was boosted by 38% compared to the pristine boron nitride nanosheets (BNNSs). Detailed fitting results showed that TC sorption on Bv-BNNSs obeyed the pseudo-second order kinetic equation and the Freundlich isotherm model. The pi − pi interaction with a multi-layered stacking form was proposed as the dominated sorption mechanism. Furthermore, DFT calculations verified that the interaction energy between Bv-BNNSs and TC was enhanced. The high activity, excellent selectivity, and remarkable durability of the Bv-BNNSs nanomaterial suggest the great potential in practical wastewater treatment.

Construction and Functional Properties of Multifunctional Chitosan Hydrogel

Hydrogel is a kind of new functional polymer material with application value and economic benefit. It has wide application in biomedical field because of its good biocompatibility and hydrophilicity.In this work, chitosan hydrogel was prepared by free radical graft copolymerization using natural biodegradable polymer chitosan as the carrier, temperature sensitive N-isopropylacrylamide (NIPAm) and pH sensitive 2‑acrylamido-2-methylpropane (AMPS) as monomers. The adsorption and drug release properties of chitosan hydrogel are discussed emphatically.The adsorption performance of chitosan hydrogel on copper ions showed that the temperature and the concentration of copper ions had influence on the adsorption. When the concentration of copper ions was 800 mg/L at 25°C, the equilibrium adsorption capacity was 225.8 mg/g, quasi-second order kinetic equation was suitable for describing the adsorption process. With the methylene blue as the drug model, the controlled release results showed that the temperature and the initial drug dosage had great effect on controlled release performance, and the cumulative release rate of 48 h was about 70%, which could achieve sustained release and controlled release to a certain extent.The experimental results also showed that the chitosan hydrogel can be completely degraded for about 20 days with excellent degradation performance. In conclusion, chitosan hydrogel has broad application prospects in drug controlled release, tissue engineering, environmental engineering and so on.

Adsorption, kinetic and mechanistic studies of Pb(II) and Cr(VI) ions using APTES functionalized magnetic biochar

Abstract Magnetic composite (Fe3O4@BC/APTES) functionalized with 3-aminopropyl triethoxysilane (APTES) was prepared by capping magnetite nanoparticles with biochar prepared from the root of C. odorata and used as adsorbent for the adsorption of Pb(II) and Cr(VI) from aqueous solution. 93.95% of Pb(II) and 52.8% of Cr(VI) were successfully adsorbed from aqueous solution by the adsorbent after 1 h at 20 °C. The Langmuir equation best described the adsorption data with maximum adsorption capacities of 64.92 mg/g (R2 = 0.97) and 48.86 mg/g (R2 = 0.92) for Pb(II) and Cr(VI) respectively. The adsorption process was investigated using the intraparticle diffusion model together with the pseudo first and second order kinetic equations. The composite was stable in an alkaline environment while 8.55% of iron was leached in an acidic medium after 1 h and the results shows Pb(II) adsorption was not affected by competing ions. Pb(II) was better adsorbed at alkaline pH as against acidic pH for Cr(VI). 88% of adsorbed Cr(VI) ion was effectively desorbed using 0.005 M HNO3 after 4 cycles. Thermodynamic parameter suggested that the sorption process was by physisorption and exothermically moderated. The composite was magnetic and easily recovered with a small bar magnet from aqueous solution after 20 s.

Efficient removal of Pb (II) by inexpensive magnetic adsorbents prepared from one-pot pyrolysis of waste tyres involved magnetic nanoparticles

A novel magnetic carbonaceous adsorbent (MCA) was prepared in low cost by pyrolysis of waste tyre rubber and corn flour with incorporated magnetic nanoparticles and used as an adsorbent to remove Pb2+ in aqueous solution. The powder of waste tyre rubber, the corn flour, and the magnetic nanoparticles were heated up to 500 ℃ at a heating rate of 10 ℃·min−1 and held isothermal for 30 min. The magnetic carbonaceous adsorbent (MCA-1050) prepared showed the maximum adsorption capacity of about 66.84 mg·g−1 for Pb2+ due to the existence of the –SH, −OH, and –COOH groups on its surface. The adsorption for Pb2+ reached the equilibrium within 50 min and the adsorption kinetics fitted to quasi–second–order kinetics equation. The adsorption thermodynamic process fitted better to the Langmuir isotherm equation than the Freundlich isotherm equation, indicating a monolayer adsorption process for Pb2+. Subsequently, in order to further learn the relationship between the structures of the carbonaceous adsorbents and pyrolysis conditions, the adsorbents were analyzed by Transmission Electron microscopy, Fourier–Transform Infrared Spectroscopy, X-ray photoelectron spectrometer, and Vibrating Sample Magnetometer. Finally, the MCA-1050 loaded with Pb2+ was eluted using EDTA solution (0.06 mol·L−1, pH 8.0), which showed good reusability and over 60% of removal rate was remained after 4 cycles.

Solar active heterojunction of p-CaFe2O4/n-ZnO for photoredox reactions

Abstract In order to enable the solar activity of ZnO and to reduce the rate of recombination of the electron–hole in the use of Ca ferrite for photoredox reaction, heterojunction composite of these two semiconductors was prepared and characterized. The solar activity of the heterojunction was determined in two separate synthetic waste waters containing Rhodamine B (RhB) and Cr (VI). The underlying mechanisms of the RhB decolourization/mineralization and Cr (VI) reduction to Cr (III) were elucidated. Within the calcination temperature and precursors combination ratios (i.e. Ca Ferrite and ZnO ratio) studied, the optimum photoredox efficiency was achieved at 500 °C and precursors combination ratio of 1:1. The SEM analysis and elemental mapping showed an even dispersion of the precursors mix. The presence of Ca Ferrite conferred solar activity and narrowed the band gap of the heterojunction. The photoluminescence spectra and electro impedance spectra showed that the recombination rate of the heterojunction was lowered than that of any of the precursors. The fitting of the time–concentration profiles of the RhB decolourization/mineralization and Cr(VI) reduction to the pseudo first order kinetic equation showed that the values of the rate constants greatly depended on the initial pollutant concentrations. While all the generated reactive species were found to be responsible for the decolourization/mineralization of RhB, the superoxide was the sole reactive species ascertained for the Cr (VI) reduction to Cr (III).

Preparation of RGO and Anionic Polyacrylamide Composites for Removal of Pb(II) in Aqueous Solution.

Graphene oxide (GO) have been reported as adsorbent materials, because its surface contains a large number of oxygen-containing groups, which provide masses of active sites. Nevertheless, it is difficult to separate GO from aqueous solution by conventional means after the end of the adsorption process. Therefore, ethylene diamine-reduced graphene oxide/anionic polyacrylamide (E-RGO/APAM), with a large quantity of adsorption sites and strong flocculation was prepared in this study. The composite E-RGO/APAM was characterized by Fourier transform infrared (FTIR), laser Raman spectrometer (IR), scanning electron microscope (SEM). The obtained results indicated that amino groups were successfully introduced into GO. Particle size test showed that the particle size of E-RGO/APAM is up to three micrometers, which can be separated from the water by conventional means, such as filtration and centrifugation, to avoid secondary pollution. The efficiency of E-RGO/APAM for removing Pb(II) was tested. The results showed that the process of adsorption of Pb(II) by E-RGO/APAM can be fitted by pseudo second order kinetic equation, indicating that the adsorption rate of the adsorbent depends on the chemisorption process, and the theoretical maximum adsorption amount of E-RGO/APAM is 400.8 mg/g. Based on these results, it can be stated that E-RGO/APAM is effective in the removal of Pb(II) from aqueous solutions, and provides a new method for the removal of heavy metal ions from industrial wastewater.

Preparation of an environmentally friendly lead adsorbent. A contribution to the rational design of heavy metal adsorbents

Abstract This work described the preparation and characterization of water insoluble chitosan derivatives as lead adsorbents. In highly regioselective reactions, N-substituted crosslinked chitosan derivatives were obtained by crosslinking native chitosan with mucic and adipic acid (a polyhydroxylated and a non-functionalized diacid of the same length chains). The crosslinking degree of the chitosan modified with adipic acid was significantly higher than that crosslinked with mucic acid (0.446 and 0.316, respectively), while the degree of substitution was almost the same (approximately 80 %). Lead adsorption isotherms were constructed at different temperatures and adjusted to well-known models, obtaining the best fit to the experimental data with Langmuir model. The lead adsorption capacity of new materials was greater than many of the adsorbents described in literature (76.3 and 69.7 mg g−1 for chitosan modified with mucic and adipic acid, respectively). Moreover, thermodynamic parameters were calculated, and results showed that the lead adsorption on the derivatives was spontaneous, exothermic, and governed by chemical interaction. Besides, kinetic studies were performed and adjusted to well-known models. The pseudo-second order kinetic equation was the one that most appropriately described the lead adsorption on the new materials. Results were consistent with the strong electrostatic attraction established between the lead cations and the free carboxylate groups of the derivatives.

Study on Ni(II) adsorption by calcium alginate beads

AbstractNickel is one of the toxic heavy metals, it is widely used in our daily lives, so there is a lot of risk of being released into the water to poison the human, flora, and fauna. In this study, we investigated the adsorption of Ni(II) on calcium alginate beads (CA), a natural polysaccharide with many outstanding advantages. The effects of initial pH, adsorptive times, and initial concentration of Ni(II) on the adsorption process were investigated. The results showed that the pH value of 3‐7.5 was favorable for the adsorption of Ni(II) on CA, the equilibrium adsorption started 60 minutes. The pseudo‐second order kinetic equation, both Langmuir and Freundlich isothermal models were fit to describe the experimental data. The maximum adsorption capacity reached 6.48 mg/g with wet alginate calcium beads, corresponding to 144 mg/g dry beads. Materials after adsorption were also studied desorption for reuse.

Application of Wastewater Reuse with Photocatalyst Prepared by Sol-Gel Method and Its Kinetics on the Decomposition of Low Molecular Weight Pollutants.

The development of immobilized photocatalyst as a strategy for problematic electronics wastewater reuse is described in this study. The strategy was to perform separate rinsing, mostly consisting of low molecular weight compounds, and to decompose them with a simple process, based on the advanced oxidation process (AOP). Extensive studies were performed on the preparation conditions of immobilized photocatalysts by sol-gel method under various amount of precursor and support, water to precursor ratio, pH, aging time, and calcination conditions. The optimized preparation conditions were chosen by measuring removal efficiencies of isopropyl alcohol as a representative target compound with supportive SEM and XRD analyses. Removal efficiencies with photocatalyst and UV irradiation in synthetic wastewater simulating electronics wastewater were evaluated over time. Removal efficiencies of alcohol, acetone, ethanol, and acetaldehyde reached 97.2%, 71.2%, 99.0%, and 99.0%, respectively, in 2 h. Reaction constants of each compound were determined by fitting experimental data to the first order kinetic equation and the trial and error method with consecutive reaction pathway. As analysis results of reaction constants, UV with prepared photocatalyst was found to be effective and the decomposition of acetone was found to be the rate-determining step. The immobilized photocatalyst developed in this study would be useful for application of wastewater reuse with high removal efficiencies, mild preparation conditions, and mechanical stability.

332 - Psychiatric disorders and Irritable Bowel Syndrome

The need to elucidate the influence of the presence of the major components (i.e. organic matter phosphate and nitrate) of nutrient-rich wastewater on the process of nutrient recovery, using calcined gastropod shell (CGS), necessitated this study. The time–concentration profiles of the recovery of organic matter, phosphate and nitrate were studied in synthetic feed water that contained single adsorbate of interest. Both the single and binary component equilibrium isotherm parameters were derived to explicate and quantify the impact of the presence of each constituent of the nutrient rich wastewater on the process of resource recovery. The time-concentration profiles of all the recovery processes showed that the process of nitrate recovery is the rate limiting step in the use of CGS as the reactive material. The pseudo second order kinetic equation gave the best description of both the nutrient and organic matter recovery but the processes were described by different equilibrium isotherm equations. The determination of the efficiency of interference on nutrient recovery showed that nitrate and organic matter exhibited minimal influence on phosphate recovery but the presence of phosphate and organic matter significantly impacted nitrate recovery. The recovery of organic matter was not vitiated by the presence of either phosphate or nitrate. The real life implications of the findings from this study showed that the use of CGS as a reactive material in resource recovery from a nutrient-rich wastewater would provide a double-pronged approach for resource recovery and appreciable treatment of wastewater for reuse.

Porous carbon materials derived from olive kernels: application in adsorption of organic pollutants.

Adsorption of organic pollutants (OPs), bisphenol A, and diuron, from aqueous solutions onto porous carbon materials (CMs) prepared from olive kernels, have been investigated. The effects of initial pH, initial OP concentration, temperature, and contact time on the adsorption capacity were studied. The adsorption of bisphenol A and diuron onto CMs was found to be optimal at pH 5.6 and 6.9, respectively. It was noticed that the adsorption of those organic pollutants from aqueous solution declined with increasing temperature and the process is exothermic. The rate of adsorption followed the second order kinetic equation. The equilibrium results showed that Langmuir model fits well with the data. The maximum adsorption capacities obtained using the best CM were 476 and 434 mg g-1 for BPA and diuron, respectively. The results showed that CMs made from olive kernels are an excellent and inexpensive biomass waste-derived sorbent. Graphical abstract.

TREATMENT OF WASTEWATER CONTAINING 2,4-DICHLOROPHENOL IN DIELECTRIC BARRIER DISCHARGE PLASMA

In the work, the processes of destruction of aqueous solutions of 2,4-dichlorophenol in a dielectric barrier discharge of atmospheric pressure in oxygen were studied. It has been experimentally shown that 2,4-dichlorophenol is destroyed in plasma quite efficiently (the degree of destruction reaches 80 %), which confirms the earlier studies on the decomposition of various organic pollutants in a dielectric barrier discharge plasma. The kinetic parameters were estimated and the main intermediate and final products of the decomposition of 2,4-dichlorophenol under the action of active plasma particles were determined. The destruction of the starting compound is described by a first order kinetic equation. The effective rate constant depends weakly on the experimental conditions and it equals to 0.56 s–1. The composition of the degradation products was studied by gas chromatography, as well as by fluorescence, spectrophotometric and potentiometric methods. Cl- in the liquid phase, as well as СО and СО2 in the gas phase, were identified as the final degradation products. And carboxylic acids and aldehydes were intermediate degradation products. But their concentrations are not high relative to СО and СО2. No molecular chlorine was detected in the gas phase. It was found that ozone does not make a significant contribution to the oxidative destruction of 2,4-dichlorophenol. The hydroxyl radicals and atomic oxygen are main active particles involved in oxidative processes. An increase in the frequency of the discharge current from 50 to 800 Hz, as well as the absence of a hydrophobic coating of the internal electrode, leads to a decrease in the decomposition rate by a factor of 1.7 (from 227 to 135 μmol/(l∙s)).