Search

The natural clay is an abundant, accessible, and low-cost material that has the potential for use in the water and wastewater industry. In this paper, Iranian natural clay and clay/Fe-Mn composite were used to remove toxic arsenic from the liquid environment. The natural clay and clay/Fe-Mn composite were characterized by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), energy-dispersive X-ray (EDX), X-ray diffractometry (XRD), thermo-gravimetric analysis (TGA), and atomic force microscopy (AFM) techniques. The effects of parameters (initial pH, temperature, sorption dose, and contact time) on the efficiency and behavior of the arsenic(V) adsorption process were studied. Freundlich (R2 = 0.945 and 0.989), Langmuir (R2 = 0.922 and 0.931), modified Langmuir (R2 = 0.921 and 0.929), and Dubinin–Radushkevich (R2 = 0.706 and 0.723) models were fitted to evaluate the equilibrium data of arsenic(V) adsorption process by natural clay and clay/Fe-Mn composite, respectively. The Langmuir adsorption capacity of arsenic(V) by the natural clay and clay/Fe-Mn composite was determined to be 86.86 mg/g and 120.70 mg/g, respectively. The arsenic(V) adsorption process followed the pseudo-second-order model. Negative values of ΔG° and ΔH° showed that the arsenic(V) sorption by the studied materials is thermodynamically spontaneous and exothermic. According to the findings, the natural clay and clay/Fe-Mn are suitable and recyclable sorbents for arsenic(V) adsorption from aqueous solutions. Also, the composite of clay with iron and manganese can improve the efficiency of clay in the removal of arsenic. [ABSTRACT FROM AUTHOR]

Efficient activated carbon was ultrasonically synthesized from the Populus alba tree, and fluoride ions were removed from samples of synthetic and real wastewaters. The effects of various parameters including pH (2–10), time (5–180 min), contaminant concentration (10–100 mg/L), sorbent dose (1–7 g/L), and co-existing ions on the fluoride removal using Populus alba activated carbon (PAAC) were revealed. The physico-chemical characteristics of PAAC were determined using SEM, FTIR, BET, XRD, and EDX mapping. The specific surface area and pore volume of the mesoporous PAAC were obtained as 707.39m2/g and 0.40 m3/g. The study found that the maximum removal efficiency of fluoride (93.37%) occurred under the fluoride concentration of 10 mg/L, PAAC of 4 g/L, pH of 6, and contact time of 100 min. The isotherms and kinetics data could be suitably reflected by the Freundlich and the pseudo-second-order kinetic models, respectively. Langmuir maximum monolayer adsorption capacity of the ultrasonic-assisted PAAC was measured as 77.12mg/g. Sorption of fluoride ions onto PAAC is feasible and an exothermic process. According to the field test, PAAC can significantly remove fluoride and other pollutants like BOD5, COD, Ni, Co, and Pb from glass and shipyard wastewater samples. [ABSTRACT FROM AUTHOR]

The present study focused on the potential of an ozone-assisted photocatalytic process using the catalyst silica-functionalized graphene oxide/ZnO coated on fiberglass (Si-GO/ZnO-FG) in the removal of toluene from waste air stream. Here, a comparative examination was performed in terms of toluene removal efficiency in the photocatalytic process (UV/Si-GO/ZnO-FG) and photocatalytic ozonation (O3/UV/Si-GO/ZnO-FG). The gaseous intermediates resulting from degradation of toluene by different processes were analyzed using GC-MS. The results of this study indicated that with the addition of ozone to the UV/Si-GO/ZnO-FG process, toluene removal increased significantly from 76.18 to 87.8%. The reason for this incremental efficiency can be explained by the fact that with the addition of ozone, the production rate and the extent of hydroxyl radical (OH•) production grow significantly; thereby, more pathways are developed for toluene degradation. The major byproducts in toluene oxidation by photocatalytic and photocatalytic ozonation processes include formic acid, acetic acid, benzyl alcohol, benzaldehyde, p-cresol, hydroquinone, and benzoic acid. Given the intermediates and the dominant oxidants detected in the aforementioned process, the possible toluene degradation pathway by the utilized process was suggested. [ABSTRACT FROM AUTHOR]

The fluoride (F) concentrations of 10 brands of cow's milk sold in Iran were analyzed and the exposure to F from milk consumption was calculated. The mean F content of the samples was 0.023 mg/L with a range of 0.014 to 0.04 mg/L. The results of this study showed that the relatively low level of F in commercially available diary milk in Iran would not be expected to cause a significant increase in the daily F intake. [ABSTRACT FROM AUTHOR]

• Metal(loid)s were detected in workers urine of gas and petrochemical companies. • Metal(loid)s were monitored in the urine before and after two weeks of work. • The urinary As level in gas workers was higher than petrochemical ones (p < 0.001). • This sequence was found for metal(loid)s in workers urine: 'As > Ni > Cd > Mn > V'. • The dust and drinking water have been effective in increasing the urine metal(loid)s. Asalouyeh (southern Iran) contains many pollution sources like petrochemical and gas refinery companies. Few studies were conducted on the body burden of metal(loid)s in occupationally exposed workers of the companies in this area. The urine concentration of metal(loid)s in workers of gas refinery and petrochemical companies in Asalouyeh (who have been worked as "two weeks work-two weeks rest" schedule) was evaluated during a before-and-after observational study. The risks of metal(loid)s in drinking water and dust particles in the studied area were also assessed. Urinary samples (n = 179) were gathered at the first day of two weeks of work (before) and at the end of two weeks of work (after). The concentration of V, Ni, Mn, Cd, and As was measured using a graphite furnace atomic absorption spectrometry. The health hazards of metal(loid)s in the air dust and drinking water of workers were also evaluated. The median concentration of metal(loid)s for workers of gas refinery and petrochemical companies for before and after two weeks of work was measured, respectively, as: As (11.44 and 9.31 μg/L), Ni (1.06 and 0.51 μg/L), Cd (0.36 and 0.31 μg/L), Mn (0.29 and 0.24 μg/L), and V (0.08 and 0.05 μg/L). After two weeks work, the median of all metal(loid)s in the urine of petrochemical and gas refinery workers was significantly increased. The non-cancer risk due to intake metal(loid)s from drinking water was more than the threshold value and the cancer risk from drinking water and inhaled air dust was less than the threshold. Our results revealed the effect of gas refinery and petrochemical activities on increasing the metal(loid)s concentration of the worker's body and the necessity to protect this group. Additionally, the metal(loid)s intake from drinking water and inhaled dust posed no cancer risk to the workers. [ABSTRACT FROM AUTHOR]

The present paper describes the sono-assisted adsorption (sono-adsorption) of methylene blue (MB), methyl violet (MV), and Nile blue (NB) from aqueous solution by AC/CoFe2O4 magnetic composite. FT-IR, TGA-DTG, VSM, XRD, TEM, SEM, EDX, Map, and Raman analysis were used to characterize the magnetic composite. The magnetization saturation value of AC/CoFe2O4 magnetic composite was determined to be 53.06 emu/g. Dye sono-adsorption efficiency was increased by increasing adsorbent dose, pH value, and contact time, but not dye concentration. Pseudo-first-order, pseudo-second-order, and intra-particle diffusion models were used to study the kinetic behavior of the cationic dye sono-adsorption. The sono-adsorption kinetics was reasonably followed by pseudo-second-order model (R2 > 0.998). The results showed that the Freundlich model (R2 > 0.976) was more able to describe the sono-adsorption equilibrium behavior than Langmuir, D-R, and Scatchard models. The maximum sono-adsorption capacity of NB, MV, and MB was determined as 86.24, 83.90, and 87.48 mg/g, respectively. Based on the parameters derived from isotherm modeling (RL, n, and E), the sono-adsorption process of cationic dyes is desirable and physical. An increase in NaCl concentration reduced the sono-adsorption efficiency for all dyes. Also, the adsorption-desorption of AC/CoFe2O4 magnetic was studied up to 10 stages, and it was confirmed that the sono-adsorption efficiency is acceptable up to the eight stage. AC/CoFe2O4 magnetic composite is, therefore, an affordable and recyclable adsorbent to remove the molecule of NB, MV, and MB dyes from aqueous media. [ABSTRACT FROM AUTHOR]

This study was designed to present a facile and effective biosorbent from Prosopis cineraria and Syzygium cumini leave (PCL and SCL) for fluoride removal. The test was done in batch mode and the effect of contact time (5, 25, 60, 90, and 120 min), initial fluoride concentration level (3, 5, 8, and 12 mg/L), and biosorbent dose (1, 3, 5, 10, and 25 g/L) on the biosorption process were examined. The optimum conditions for the maximum fluoride removal were occurred at 1 g/L biosorbent dose and contact time of 120 (for PCL) and 90 min (for SCL). The results suggested that the pseudo‐second‐order and Langmuir isotherm models described the experimental data well. According to the Langmuir model, the maximum adsorption capacity of fluoride for PCL and SCL was attained 11.52 and 7.4 mg/g, respectively. Based on Boyd and intra‐diffusion models, the biosorption of fluoride onto PCL and SCL was mainly controlled by film‐diffusion. The study revealed the potential use of PCL and SCL as two new effective biosorbents for the removal of fluoride from aqueous solution. © 2019 American Institute of Chemical Engineers Environ Prog, 38: S429–S440, 2019 [ABSTRACT FROM AUTHOR]

The purpose of this research was the preparation of Tamarix hispida biochar during a pyrolysis process and then improvement its fluoride adsorption capacity by lanthanum chloride. The biochar powder was amended by lanthanum during a precipitation‐oxidation method to make biochar–lanthanum (biochar–La). Adsorbent characteristics of the fresh and fluoride loaded biochar–La were determined by using Fourier‐transform infrared spectroscopy spectrometer, Brunauer–Emmett–Teller, pH of zero point charge, energy‐dispersive X‐ray spectroscopy, and scanning electron microscopy methods. The mesoporous adsorbent had a surface area of 164.5 m2/g. Effects of some important factors such as initial fluoride concentration (20, 40, and 70 mg/L), biochar–La dose (1–10 g/L), contact time (3–100 min), solution temperature (25–50°C), and initial pH (2–10) were tested. The results showed that fluoride uptake by modified biochar is much more effective than simple one. The adsorption data well followed the Langmuir isotherm (maximum adsorption capacity = 164.23 mg/g) and second‐order kinetic model. Increasing the amount of biochar–La and fluoride concentration was led to increasing and reducing the adsorption efficiency, respectively. The biochar–La adsorbent had a good performance at sixth cycle of reuse (>50% removal). The fluoride content in a real wastewater was reduced from 23 mg/L to around 3 mg/L at conditions of biochar–La: 5 g/L, time: 50 min, and original pH: 6.8. © 2018 American Institute of Chemical Engineers Environ Prog, 38: S298–S305, 2019 [ABSTRACT FROM AUTHOR]

In the current study, the bio-adsorption potential of Callinectes sapidus biomass for control of cadmium, nickel, and lead from the aqueous stream was assessed. Spectrum analysis of FTIR, AFM, EDAX, mapping, SEM, TEM, and XRF was used to study the properties of the C. sapidus biomass. The XRF analysis revealed that C. sapidus bio-adsorbent has various effective metal oxides that can be useful to adsorb pollutants. The best model to describe the equilibrium data was Freundlich isotherm. The Langmuir bio-adsorption capacity was reported at 31.44 mg g−1, 29.23 mg g−1, and 29.15 mg g−1 for lead, cadmium, and nickel ions, respectively. Pseudo-first-order and pseudo-second-order kinetic models were studied to test the kinetic behavior of the process. An intra-particle diffusion model was used to determine the effective mechanisms involved in the bio-adsorption. Based on t1/2, it can be concluded that the equilibrium speed of the bio-adsorption process is high. The thermodynamic study showed that the metal bio-adsorption process using C. sapidus biomass is exothermic and spontaneous. The field applicability of the crab bio-adsorbent for eliminating concurrently several contaminants (metal ions, antibiotics, sulfate, nitrate, and ammonium) from an actual wastewater was successfully examined. [ABSTRACT FROM AUTHOR]

This research has analysed the physiochemical properties of a catalyst that has been developed - biochar-La, including BJH, BET, EDX, SEM, FTIR, pHpzc, and iodine number. The catalyst consisted of effective functional groups, including C=S, C-O, C=C, -COOH and O-H, with a specific surface area of 31.2 m2/g. The catalyst was used in the biochar-La/ultrasonic/persulphate system to remove phenol from wastewater. The kinetics, mechanism, and reusability of the catalyst for the phenol removal from synthetic wastewater were determined. The results suggested that phenol removal kinetics follows pseudo-first-order model (k = 0.0386 1/min), and the catalyst can be reused three times. The potential of operation of the biochar-La/ultrasonic/persulphate system - with the effective removal of phenol and other organic compounds from real petrochemical wastewater - was tested. The results indicated that the removal of phenol from the petrochemical wastewater with a relatively high total dissolved solid is >99%. The gas chromatography-mass spectrometry (GC-mass) test revealed that the complete decomposition of some contaminants in the petrochemical wastewater had occurred, as H2O and CO2 were detected. The contribution of a heterogeneous mechanism for phenol oxidation by biochar-La/ultrasonic/persulphate was calculated to be 60%. Overall, the results showed that the biochar-La/ultrasonic/persulphate system is very effective and promising for the removal of phenol from the petrochemical wastewater. [ABSTRACT FROM AUTHOR]

This study reports a new approach of alga amendment in a live mode. The Caulerpa sertularioides alga was modified with sulfur-containing materials of methionine (C5H11NO2S) and sodium sulfate (Na2SO4) to more concentrate the sulfur content of the yielded biomass (adsorbent). The simple and amended C. sertularioides alga was fully characterized with FTIR, SEM, EDX, BET, BJH, and pHzpc techniques. The copper adsorption from aqueous media was done by three adsorbents of C. sertularioides-simple (CSS), C. sertularioides-Na2SO4 (CSN), and C. sertularioides-C5H11NO2S (CSC). The parameters of pH (2-6), adsorbent dosage (2-10 g/L), and contact time (3-80 min) were optimized at 5, 5 g/L, and 60 min, respectively. According to Langmuir isotherm (the best-fitted model), the maximum adsorption capacity of CSN (98.04 mg/g) was obtained 2.4 times higher than CSC (40.73 mg/g) and 9.5 times higher than CSS (10.29 mg/g). The Cu adsorption process by the adsorbents was best-fitted pseudo-second-order kinetic model. The CSN, CSC, and CSS biomasses were successfully reused 5, 4, and 4 times, respectively. The thermodynamic study revealed that the copper adsorption process by CSN is exothermic and non-spontaneous. Finally, the suitability of adsorbents prepared from algae was tested by cleaning a simulated wastewater. [ABSTRACT FROM AUTHOR]

A beta type-chitin was produced from the shell of Penaeuse semisulcatuse shrimp for removal of lead and cadmium from the aqueous environment. Full physicochemical properties of the chitin (FTIR, SEM, mapping, XRD, EDX, AFM, and TGA-DTG) were obtained. Effects of solution pH, chitin dose, metals concentration, and contact time on the lead and cadmium adsorption were assessed. The solution pH had a great influence on the metal removal. Pseudo-first and pseudo-second order models were used to evaluate the kinetic behavior of metals adsorption by P. semisulcatuse chitin. Freundlich isotherm model was slightly better than the Langmuir model to describe the adsorption data. The RL value (obtained from the Langmuir model) for the adsorption of lead and cadmium was calculated to be 0.027 and 0.133, respectively, which showed the metals adsorption process by the chitin is desirable. The maximum adsorption capacity of lead and cadmium by P. semisulcatuse chitin was determined 13.14 mg/g and 19.15 mg/g, respectively. To desorb the adsorbed-metal from the chitin, the 1M HNO3 solution was applied and the heavy metals desorption was suitable (90%). The half life (t1/2) factor in the adsorption of Pb and Cd onto chitin was calculated 2.817 min and 3.876 min, respectively. [ABSTRACT FROM AUTHOR]

Activated carbon (AC) was synthesized from Phoenix dactylifera stones and then modified by CoFe2O4 magnetic nanocomposite for use as a Cr(VI) adsorbent. Both AC/CoFe2O4 composite and AC were fully characterized by FTIR, SEM, XRD, TEM, TGA, and VSM techniques. Based on the surface analyses, the addition of CoFe2O4 nanoparticles had a significant effect on the thermal stability and crystalline structure of AC. Factors affecting chromium removal efficiency like pH, dosage, contact time, temperature, and initial Cr(VI) concentration were investigated. The best pH was found 2 and 3 for Cr adsorption by AC and AC/CoFe2O4 composite, respectively. The presence of ion sulfate had a greater effect on the chromium sorption efficiency than nitrate and chlorine ions. The results illustrated that both adsorbents can be used up to seven times to adsorb chromium. The adsorption process was examined by three isothermal models, and Freundlich was chosen as the best one. The experimental data were well fitted by pseudo-second-order kinetic model. The half-life (t1/2) of hexavalent chromium using AC and AC/CoFe2O4 magnetic composite was obtained as 5.18 min and 1.52 min, respectively. Cr(VI) adsorption by AC and AC/CoFe2O4 magnetic composite was spontaneous and exothermic. In general, our study showed that the composition of CoFe2O4 magnetic nanoparticles with AC can increase the adsorption capacity of AC from 36mg/L to 70mg/L. [ABSTRACT FROM AUTHOR]