Experimentally and spectroscopically evidenced mechanistic study of butyl peroxyacid oxidative degradation of benzo[a]pyrene in soil.

Benzo[a]pyrene (BaP) is a major indicator of soil contamination and categorized as a highly persistent, carcinogenic, and mutagenic polycyclic aromatic hydrocarbon. An advanced peroxyacid oxidation process was developed to reduce soil pollution caused by BaP originating from creosote spills from railroad sleepers. The pH, organic matter, particle size distribution of soil, and concentrations of BaP and heavy metals (Cd, Cu, Zn, Pb, and As) in the BaP-contaminated soils were estimated. A batch experiment was conducted to determine the effects of organic acid type, soil particle size, stirring speed, and reaction time on the peroxyacid oxidation of BaP in the soil samples. Additionally, the effect of the organic acid concentration on the peroxyacid degradation of BaP was investigated using an oxidizing agent in spiked soil with and without hydrogen peroxide. The results of the oxidation process indicated that BaP and heavy metal residuals were below acceptable Korean standards. A significant difference in the oxidative degradation of BaP was observed between the spiked and natural soil samples. The formation of a peroxyacid intermediate was primarily responsible for the enhanced BaP oxidation. Further, butyric acid could be reused thrice without losing the efficacy (<90%). The systematic peroxyacid oxidative degradation mechanism of BaP was also discussed. A qualitative analysis of the by-products of the BaP reaction was conducted, and their corresponding toxicities were determined for possible field applications. The findings conclude that the developed peroxyacid oxidation method has potential applications in the treatment of BaP-contaminated soils.

Application of cadmium-doped ZnO for the solar photocatalytic degradation of phenol.

In this study, photocatalysis of phenol was studied using Cd-ZnO nanorods, which were synthesized by a hydrothermal method. The Cd-ZnO photocatalyst was characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy, and Fourier transform infrared (FT-IR) and UV-Vis spectroscopy. XRD patterns exhibit diffraction peaks indexed to the hexagonal wurtzite structures with the P63mc space group. SEM images showed that the average size of the Cd-ZnO nanorods was about 90 nm. Moreover, the nanorods were not agglomerated and were well-dispersed in the aqueous medium. FT-IR analysis confirmed that a surface modifier (n-butylamine) did not add any functional groups onto the Cd-ZnO nanorods. The dopant used in this study showed reduction of the bandgap energy between valence and conduction of the photocatalyst. In addition, effect of various operational parameters including type of photocatalyst, pH, initial concentration of phenol, amount of photocatalyst, and irradiation time on the photocatalytic degradation of phenol has been investigated. The highest phenol removal was achieved using 1% Cd-ZnO for 20 mg/l phenol at pH 7, 3 g/l photocatalyst, 120 min contact time, and 0.01 mole H2O2.

Application of Scallop shell-Fe3O4 nanoparticles for the removal of Cr(VI) from aqueous solutions.

In this study, removal of Cr(VI) by Scallop shell-Fe3O4 nanoparticles was investigated with variation of pH, adsorbent dosage, initial Cr(VI) concentration, ionic strength and temperature. Coating of Fe3O4 nanoparticles onto Scallop shell was identified by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy and energy dispersive X-ray analysis. The maximum adsorption was observed at pH 3. Removal efficiency of Cr(VI) was increased with increasing adsorbent dosage, but was decreased with increasing initial Cr(VI) concentration and temperature. Removal efficiency of Cr(VI) was decreased in the presence of sulfate and carbonate ions. Adsorption kinetic study revealed that a pseudo-second order model better described the removal data than a pseudo-first order model and an intra-particle diffusion model. Maximum adsorption capacity was estimated to be 34.48 mg/g. Thermodynamic studies indicated that adsorption of Cr(VI) onto Scallop shell-Fe3O4 nanoparticles occurred via an exothermic (ΔH = -320.88 KJ mol-1) process. Adsorption efficiency of Cr(VI) by Scallop shell-Fe3O4 nanoparticles was maintained even after eight successive cycles.

Rapid degradation of phenol by ultrasound-dispersed nano-metallic particles (NMPs) in the presence of hydrogen peroxide: A possible mechanism for phenol degradation in water.

The present study was carried out to investigate the degradation of phenol by ultrasonically dispersed nano-metallic particles (NMPs) in an aqueous solution of phenol. Leaching liquor from automobile shredder residue (ASR) was used to obtain the NMPs. The prepared NMPs were analyzed by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and by X-ray diffraction (XRD). The SEM images show that the diameters of the NMPs were less than 50 nm. An SEM-EDX elemental analysis reveals that Fe was the most commonly found element (weight %) in the NMPs. The FTIR and XRD peaks indicate the presence of metals oxides on the surfaces of the NMPs. The results of the XPS analysis indicate that various elements (e.g., C, O, Zn, Cu, Mn, Fe) are present on the surfaces of the NMPs. The effects of the NMP dose, the initial solution pH, and of different concentrations of phenol and H2O2 on the phenol degradation characteristics were evaluated. The results of this study demonstrate that phenol degradation can be improved by increasing the amount of NMPs, whereas it is reduced with an increase in the phenol concentration. The degradation of phenol by ultrasonically dispersed NMPs followed the pseudo-first-order kinetics. The probable mechanism of phenol degradation by ultrasonically dispersed NMPs was the oxidation of phenol caused by the hydroxyl radicals produced during the reaction between H2O2 and the NMPs during the ultrasonication process.

Photocatalytic reduction of hexavalent chromium with illuminated amorphous FeOOH.

In this study, photocatalytic reduction of hexavalent chromium [Cr(VI)] by amorphous FeOOH was investigated with variations in FeOOH dosage, pH, initial Cr(VI) concentration, purging gas, organic compounds and initial hydrogen peroxide concentration. Reduction and adsorption were identified as important processes for the removal of Cr(VI). FeOOH dosage was also an important parameter for the removal of Cr(VI). As the FeOOH dosage increased up to 0.5 g/L, the removal of Cr(VI) was continuously enhanced and then decreased above 0.5 g/L due to increased blockage of the incident UV light. The removal efficiency of Cr(VI) decreased with increasing pH, initial Cr(VI) concentration and initial hydrogen peroxide concentration. While the removal efficiency of Cr(VI) increased with purging of nitrogen gas compared to that of oxygen gas because of less competition between dissolved oxygen and Cr(VI) with the electron in the conduction band of FeOOH. The photocatalytic reduction of Cr(VI) was increased in the presence of citric acid and phenol, while it was decreased in the presence of EDTA and oxalic acid. The reaction rate constant (kobs) was decreased from 0.2141 to 0.0026 1/min and the value of electrical energy per order (EEo) was increased from 22.41 to 1846.15 (kWh/m3) with increasing initial Cr(VI) concentration from 10 to 50 mg/L, respectively. Finally, proper photocatalytic activity was maintained even after five successive cycles.

Oxidation of sulphide in abandoned mine tailings by ferrate.

In this study, Fe(VI) was applied to treat three mine tailings containing different amounts of sulphides and heavy metals. Oxidation of sulphides by Fe(VI) was studied at pH 9.2 with variation of solid to solution ratio, Fe(VI) concentration and injection number of Fe(VI) solution. The major dissolved products from the treatment of mine tailings with Fe(VI) solution were sulphate and arsenic. Oxidation efficiency of sulphides was evaluated by reduction efficiency of Fe(VI) as well as by measurement of dissolved sulphate concentration. Even though inorganic composition of three mine tailings was different, reduction fraction of Fe(VI) was quite similar. This result can suggest that Fe(VI) was involved in several other reactions in addition to oxidation of sulphides. Oxidation of sulphides in mine tailing was greatly dependent on the total amount of sulphides as well as kinds of sulphides complexed with metals. Over the five consecutive injections of Fe(VI) solution, dissolved sulphate concentration was greatly decreased by each injection and no more dissolved sulphate was observed at the fifth injection. While dissolved arsenic was decreased lineally up to the fifth injection. Sulphate generation was slightly increased for all mine tailings as Fe(VI) concentration was increased; however, enhancement of oxidation efficiency of sulphides was not directly proportional to the initial Fe(VI) concentration.

Iron oxide impregnated Morus alba L. fruit peel for biosorption of Co(II): biosorption properties and mechanism.

Biosorption is an ecofriendly wastewater treatment technique with high efficiency and low operating cost involving simple process for the removal of heavy metal ions from aqueous solution. In the present investigation, Morus alba L. fruit peel powder (MAFP) and iron oxide impregnated Morus alba L. fruit peel powder (IO-MAFP) were prepared and used for treating Co(II) contaminated aqueous solutions. Further the materials were characterized by using FTIR and SEM-EDX analysis. From FT-IR analysis it was found that hydroxyl, methoxy, and carbonyl groups are responsible for Co(II) biosorption. The kinetic data obtained for both biosorbents was well fitted with pseudo-second-order kinetic model. The equilibrium data was in tune with the Langmuir and Freundlich isotherm models. The thermodynamic studies were also carried and it was observed that sorption process was endothermic at 298-328 K. These studies demonstrated that both biosorbents were promising, efficient, economic, and biodegradable sorbents.

Application of ferrate for the treatment of metal-sulfide.

Fe(VI) was evaluated to treat metal-sulfides such as Fe-S, Pb-S, Cu-S and Cd-S contained in mine tailings known to generate acidic mine drainages. The rate of Fe(VI) reduction was dependent on the type of metal-sulfide as well as the concentration of each metal-sulfide. Fe(VI) reduction increased as the concentration of each metal-sulfide increased. The order of initial rates for the Fe(VI) reduction was Pb-S > Cu-S > Fe-S > Cd-S. The rate of Fe(VI) reduction by each metal sulfide increased as the ionic strength increased. For all metal sulfides, reduction efficiency of Fe(VI) was not affected by the presence of different background electrolytes except NaNO(2) and Na(2)SO(3). This result suggests that fully oxidized anions such as [Formula: see text] , [Formula: see text] , [Formula: see text] as well as redox insensitive anion such as Cl(-) are not involved in the redox reaction between Fe(VI) and metal sulfides.

Photocatalytic removal of Escherichia coli from aquatic solutions using synthesized ZnO nanoparticles: a kinetic study.

Development of effective and low-cost disinfection technology is needed to address the problems caused by an outbreak of harmful microorganisms. In this work, an effective photocatalytic removal of Gram-negative bacteria Escherichia coli from aqueous solution was reported by using ZnO nanoparticles under UV light irradiation. The effect of various parameters such as solution pH, ZnO dosage, contact time and initial E. coli concentration were investigated. Maximum photocatalytic disinfection was observed at neutral pH because of the reduced photocatalytic activity of ZnO at low and high pH values originated from either acidic/photochemical corrosion of the catalyst and/or surface passivation with Zn(OH)(2). As the ZnO dosage increased, the photocatalytic disappearance of E. coli was continuously enhanced, but was gradually decreased above 2 g/L of ZnO due to the increased blockage of the incident UV light used. The optimum ZnO dosage was determined as 1 g/L. Photocatalytic removal of E. coli decreased as initial E. coli concentration increased. Three kinetic models (zero-, first- and second-order equations) were used to correlate the experimental data and to determine the kinetic parameters.

Improving the clean-up efficiency of field soil contaminated with diesel oil by the application of stabilizers.

Fenton-like oxidation in the presence of stabilizers has been applied in batch and column reactors to treat field soils contaminated with diesel oil. Citrates, ethylene diamine tetra-acetic acid (EDTA), ethylene diamine disuccinic acid (EDDS) and phosphates were assessed as stabilizers. The stability of hydrogen peroxide in the soil was evaluated by varying the concentration of each stabilizer and hydrogen peroxide. In a batch test, the residual concentration of hydrogen peroxide was shown to be directly related to the concentration of these stabilizers. Citrate showed the greatest stabilizing effect of the four stabilizers for hydrogen peroxide and 0.05 M was selected as the optimum dosage. In order to investigate the effect of stabilizer on the efficiency of removal of total petroleum hydrocarbons (TPH) in a column reactor, 30 mL of each stabilizer solution at pH 3 and containing 15% hydrogen peroxide was injected. The batch result confirmed that the greatest TPH removal took place in the presence of citrate in a column reactor. The order of TPH removal in the presence of stabilizers was: citrate > H3PO4 > EDDS > EDTA. TPH removal was affected by the concentration of stabilizer and the initial concentration of TPH. When 0.05 M citrate solution containing 15% hydrogen peroxide was applied to four field soils and an artificially contaminated soil, similar or better TPH removal was observed in the field soils compared to the artificially contaminated soil. This result suggests that Fenton-like oxidation with stabilizer can be effective in restoring field soils contaminated with diesel oil.

Facile provision of CuO-Kaolin nanocomposite for boosted sonocatalytic removal of Cr(VI) from hydrous media.

Nowadays, nanoscale materials have been widely applied in the removal of contaminants from the water system. Reduction of Cr(VI) (as a poisonous species) to Cr(III) (as a slight toxic species) was performed using CuO-Kaolin with ultrasound (US) irradiation. The CuO-Kaolin nanocomposite was synthesized via a facile co-precipitation method. Then X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscope and Energy dispersive X-ray spectroscopy analyses were performed to identify the structural features of CuO-Kaolin. The role of influential parameters for the reduction of Cr(VI) was investigated in sonocatalytic advanced oxidation system. About 89.35% of Cr(VI) was removed via US/CuO-Kaolin process after 90 min at optimum conditions (pH = 3, sonocatalyst dosage = 1 g L-1 and [Cr (VI)]0 = 20 mg L-1). This outstanding result was due to the synergistic effect of the increased electron delivery to conduction band on CuO-Kaolin nanocomposite and the increased reactive surface region of nanoparticles by sonication. The presence of H2O2 as an amplifier improved the removal efficiency of Cr(VI) from 89.35% to 100% after 20 min. Kinetic experimental results were well described by a pseudo-first-order kinetic model. Desorption experiments showed excellent stability of sonocatalyst during the reaction and maintenance of the catalytic activity up to 10 sequential cycles.

Design and modeling of diazinon degradation in hydrous matrix by Ni-doped ZnO nanorods under ultrasonic irradiation: process optimization using RSM (CCD), kinetic study, reaction pathway, mineralization, and toxicity assessment.

In first, the Ni-doped ZnO nanorods used as an appeal sonocatalyst was synthesized through co-precipitation method. Afterwards, the crystalline structure, functional groups, surface morphology, and elemental composition were characterized by a set of analysis. Removal of diazinon ((DZ) as a renowned pesticide) was investigated using sonocatalytic performance of US/Ni-doped ZnO system. In this empirical study, response surface methodology (RSM) based central composite design (CCD) was applied for optimization of operational factors. Under the optimum conditions such as initial pH = 5, initial DZ concentration = 15 mg L-1, sonocatalyst dosage = 1 g L-1, and in the presence of organic compounds (oxalic acid, humic acid, and folic acid) = 3 mg L-1, the sonocatalytic degradation of DZ after 15 min was 82.29%. The F-value (6.64) and P-value (< 0.0001) for DZ degradation in the quadratic model imply the proposed model was significant. A-factor (pH) considers as a prominent factor owing to having the highest F-value. In addition, the sonocatalytic data in this study exhibited valid fitting for the first order kinetic model (R2 > 0.98). After six consecutive cycles, the Ni-doped ZnO nanorods could be recyclable for sonocatalytic degradation of DZ. The five main compounds produced during the US/Ni-doped ZnO embracing 2-isopropyl-6-methyl-4-pyrimidinol (IMP), diethyl phosphonate, diazoxon, hydroxyldiazinon, and diazinon methyl ketone are formed in the path of DZ degradation. OFAT style also revealed 99.99% of DZ degradation with 73.26% of mineralization rate in optimum status. The Ni-doped ZnO presented agreeable sonocatalytic facility in the refinement of real water and wastewater matrix. Finally, the results of toxicity evaluation (Daphnia magna) in the sonocatalytic degradation of DZ (by US/Ni-doped ZnO system) showed that the toxicity of the DZ solution lessened under US waves (LC50 and TU 48 h equal to 36.472 and 2.741 volume percent, respectively).

Development of ultra-high surface area polyaniline-based activated carbon for the removal of volatile organic compounds from industrial effluents.

Removing volatile organic compounds (VOCs) from aqueous solutions is critical for reducing VOC emissions in the environment. Activated carbons are widely used for removal of VOCs from water. However, they show less application feasibility and low removal due to less surface area. Here, a cost-effective and high surface area activated carbonized polyaniline (ACP) was synthesized to sustainable removal of VOCs from water. The ACP microstructure, surface properties, and pore structure were investigated using Brunauer-Emmett-Teller (BET) theory, Scanning Electron Microscopy (SEM), and Transmission Electron Microscopy (TEM). The specific surface area of ACP6:1 (2988.13 m2/g) was greater than that of commercial activated carbon (PAC) (1094.49 m2/g), indicating that it has excellent VOC adsorption capacity. The effects of pH, initial VOC concentration, time, temperature, and ionic strength were studied. According to kinetic and thermodynamic studies on VOCs adsorption, it is an exothermic and spontaneous process involving rate-limiting kinetics. Adsorption isotherms follow the Freundlich isotherm model, suggesting that the adsorbent surface is heterogeneous with multilayer adsorption and maximum ACP adsorption capacities of 1913.9, 2453.3, 1635.8, and 3327.0 mg/g at 293 K for benzene, toluene, ethylbenzene, and perchloroethylene, respectively, representing a 3- to 5-fold improvement over PAC. ACP is a promising adsorbent with a high adsorption efficiency for VOC removal.

Efficiency of Ppy-PA-pani and Ppy-PA composite adsorbents in Chromium(VI) removal from aqueous solution.

In this study, first time the combination of composites with Phytic acid (PA) as the organic binder cross-linker is reported. The novel use of PA with single and double conducting polymers (polypyrrole (Ppy) and polyaniline (Pani)) were tested against removal of Cr(VI) from wastewater. Characterizations (FE-SEM, EDX, FTIR, XRD, XPS) were performed to study the morphology and removal mechanism. The adsorption removal capability of Polypyrrole - Phytic Acid - Polyaniline (Ppy-PA-Pani) was deemed to be higher than Polypyrrole - Phytic Acid (Ppy-PA) due to the mere existence of Polyaniline as the extra polymer. The kinetics followed 2nd order with equilibration at 480 min, but Elovich model confirmed that chemisorption is followed. Langmuir isotherm model exhibited maximum adsorption capacity of 222.7-321.49 mg/g for Ppy-PA-Pani and 207.66-271.96 mg/g for Ppy-PA at 298K-318K with R2 values of 0.9934 and 0.9938 respectively. The adsorbents were reusable for 5 cycles of adsorption-desorption. The thermodynamic parameter, ΔH shows positive values confirmed the adsorption process was endothermic. From overall results, the removal mechanism is believed to be chemisorption through Cr(VI) reduction to Cr(III). The use of phytic acid (PA) as organic binder with combination of dual conducting polymer (Ppy-PA-Pani) was invigorating the adsorption efficiency than just single conducting polymer (Ppy-PA).

Removal of arsenic from aqueous solution by iron-coated sand and manganese-coated sand having different mineral types.

In this study, the effects of the coating temperature during the preparation of manganese-coated sand (MCS) and iron-coated sand (ICS) on the removals of As(III) and As(V) were evaluated. The mineral type of manganese oxide on MCS-150, prepared at 150 °C, was identified as a mixture of pyrolusite and ramsdellite, which changed to high crystalline pyrolusite above 300 °C. The mineral type of ICS-150, prepared at 150 °C, was a mixture of goethite and hematite, which changed to high crystalline goethite above 300 °C. The adsorption efficiency was determined according to the mineral type which depended on the coating temperature. The As(III) oxidation efficiency of MCS-150 and As(V) adsorption efficiency of ICS-150 were approximately 77 and 70% higher compared with those of MCS-600 and ICS-600, respectively, prepared at 600 °C. Regardless of the coating temperature, the amounts of manganese and iron coated on the sand substrates were similar.

Bacterial removal in flow-through columns packed with iron-manganese bimetallic oxide-coated sand.

The objective of this study was to investigate the performance of iron-manganese bimetallic oxide-coated sand (IMCS) in the removal of bacteria (Escherichia coli ATCC 11105) using small-scale (length = 20 cm, inner diameter = 2.5 cm) and 30-day long-term (length = 50 cm, inner diameter = 2.5 cm) column experiments. Results indicated that the bacterial removal capacity of IMCS (q(eq) = 0.66 g/g) was slightly lower than that of iron oxide-coated sand (ICS) (q(eq) = 0.69 g/g) but about two times greater than those of manganese oxide-coated sand (MCS, q(eq) = 0.30 g/g) and dual media containing ICS and MCS (q(eq) = 0.35 g/g). In IMCS, increasing the flow rate from 0.5 to 3.0 mL/min decreased the removal capacity from 1.14 to 0.64 g/g. Nitrate showed an enhancement effect on the removal capacity of IMCS at 1 and 10 mM, while phosphate and bicarbonate had both hindrance (1 mM) and enhancement (10 mM) effects, depending on their concentrations. The long-term column experiment (bacterial injection conc. = 4.2 × 10(6) CFU/mL) showed that IMCS could remove more than 99.9 % of bacteria within 13 days (effluent conc. = 1.6 × 10(2) CFU/mL). This study demonstrated that IMCS could be used as an adsorptive filter medium for bacterial removal in water treatment.

Application of activated carbon impregnated with metal oxides to the treatment of multi-contaminants.

In this study, as a novel technique for the simultaneous treatment of As(III) and phenol in a single column reactor, different ratios of manganese-impregnated activated carbon (Mn-AC) and iron-impregnated activated carbon (Fe-AC) were applied in a bench-scale column reactor. In this bench-scale test, the column system packed with both Mn-AC and Fe-AC (binary system) was identified as the best system due to the good oxidation efficiency of As(III) to As(V) by Mn-AC, which reasonably controlled the mobility of total arsenic through adsorption of As(V), along with efficient removal of phenol . When the pilot-scale column reactor, packed with equal amounts of Mn-AC and Fe-AC, was applied for the removal of As(III) and phenol, the oxidation of As(III) by 1 g of Mn-AC for up to 110 days and the removal of phenol by total 1 g of Mn-AC and Fe-AC for up to 100 days were 1.81 x 10(-4) g and 8.20 x 10(-4) g, respectively. Based on this work, Fe-AC and Mn-AC can be regarded as a promising filter material in the treatment of wastewater contaminated with organic compounds, such as phenol, and redox-sensitive ions, such as As(III).

Portable SA/CMC entrapped bimetallic magnetic fly ash zeolite spheres for heavy metals contaminated industrial effluents treatment via batch and column studies.

Heavy metals are perceived as a significant environmental concern because of their toxic effect, bioaccumulation, and persistence. In this work, a novel sodium alginate (SA) and carboxymethylcellulose (CMC) entrapped with fly ash derived zeolite stabilized nano zero-valent iron and nickel (ZFN) (SA/CMC-ZFN), followed by crosslinking with CaCl2, is synthesized and applied for remediation of Cu(II) and Cr(VI) from industrial effluent. The characterization of the adsorbent and its surface mechanism for removing metals were investigated using advanced instrumental techniques, including XRD, FT-IR, SEM-EDX, BET, and XPS. The outcomes from the batch experiments indicated that monolayer adsorption on homogeneous surfaces (Langmuir isotherm model) was the rate-limiting step in both heavy metals sorption processes. The maximum adsorption capacity of as-prepared SA/CMC-ZFN was 63.29 and 10.15 mg/g for Cu(II) and Cr(VI), respectively. Owing to the fact that the wastewater released from industries are large and continuous, a continuous column is installed for simultaneous removal of heavy metal ions from real industrial wastewater. The outcomes revealed the potential of SA/CMC-ZFN as an efficient adsorbent. The experimental breakthrough curves fitted well with the theoretical values of Thomas and Yoon-Nelson models. Overall, the results indicated that SA/CMC-ZFN is a viable, efficient, and cost-effective water treatment both interms of batch and column processes.

Magnetic-watermelon rinds biochar for uranium-contaminated water treatment using an electromagnetic semi-batch column with removal mechanistic investigations.

Biosorption using modified biochar has been increasingly adopted for the sustainable removal of uranium-contaminated from an aqueous solution. In this research study, the facile preparation and surface characteristics of magnetized biochar derived from waste watermelon rind to treat U(VI) contaminated water were investigated. The porosity, specific surface area, adsorption capacity, reusability, and stability were effectively improved after the magnetization of biochar. The kinetics and isotherm studies found that the U(VI) adsorption was rate-limiting monolayer sorption on the homogeneous surface of magnetized watermelon rind biochar (MWBC). The maximum adsorption capacity was found to be 323.56 mg of U(VI) per g of MWBC at pH 4.0 and 293 K that was higher than that of watermelon rind biochar (WBC) (135.86 mg g-1) and other sourced biochars. The surface interaction mechanism, environmental feasibility, applicability for real-filed water treatment studied in the electromagnetic semi-batch column, and reusability of MWBC were also explored. Furthermore, salient raised the ion exchange and complexation action capacity of MWBC due to the presence of Fe oxide. The overall results indicated that MWBC was not only inexpensive and had a high removal capacity for U(VI), but it also easily enabled phase separation from an aqueous solution, with more than three times reusability at a minimum removal capacity of 99%.

Applicability of poorly crystalline aluminum oxide for adsorption of arsenate.

This study examined the characteristics of arsenate adsorption on poorly crystalline oxide (PCAO) which was obtained from recycling of dry sanding powders (DSP) produced during sanding and sawing process in a decorative interior company. After calcinating DSP at 550°C, poorly crystalline oxide (PCAO) was obtained as an adsorbent. From the batch adsorption experiments, arsenate was completely removed up to the concentration of 10 mg/L by PCAO. The stability of PCAO as an adsorbent was evaluated at pH 7 and found that the arsenate adsorbed on PCAO was stable for 24 h. The predominant interaction between arsenate and PCAO was thought to be a strong chemical bond by spectroscopic analysis. The arsenate adsorption behavior onto PCAO was satisfactorily simulated with MINEQL+, suggesting that arsenate formed inner-sphere complexes with the surface of PCAO by chemisorption. Meanwhile, the presence of competitive anions such as PO(4) (3-), SO(4) (2-) and CO(3) (2-) decreased somewhat the removal efficiency of arsenate and the effects of competing anions on the adsorption of arsenate were in the order of PO(4) (3-) > SO(4) (2-) > CO(3) (2-) under pH 6. The application of PCAO to the real mine drainage was also carried out. Although the adsorption of arsenic on the PCAO was slightly decreased rather than that removed from synthetic wastewater due to competitive sorption by multiple ions, it was possible to meet the national discharge standard limit with increasing adsorbent concentration.