Magnetic hydrochar grafted-chitosan for enhanced efficient adsorption of malachite green dye from aqueous solutions: Modeling, adsorption behavior, and mechanism analysis.

Water pollution by organic dyes is one of the most serious environmental problems worldwide. Malachite green (MG) is considered as one the serious organic dyes which is discharged in wastewater by leather and textile manufacturing plants. MG dye can cause severe hazards to the environment and human health. Therefore, the removal of MG dye from wastewater is very important and essential. This study aims to synthesize a new magnetic hydrochar grafted to chitosan (MWSHC@CS) for the removal of MG dye from the aqueous solutions. Transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area, and Zeta potential analysis were used to characterize the synthesized MWSHC@CS. Batch experiments were conducted to optimize MG dye adsorption conditions, including adsorbent mass, pH, temperature, initial concentration, and contact time. The results revealed that MWSHC@CS had an excellent removal efficiency (96.47 %) for MG dye at the optimum condition (at m: 20 mg, pH: 7.5, t: 420 min, and T: 298 K). Adsorption isotherms outcomes revealed the MG adsorption data were best fit by the Langmuir model with a maximum adsorption capacity (420.02 mg/g). Adsorption kinetics outcomes exhibited that the adsorption process of MG dye fitted well to the Elovich model. The thermodynamic results revealed that the adsorption process was physical, exothermic, and spontaneous. The adsorption mechanisms of MG onto MWSHC@CS were hydrogen bonding, electrostatic interaction, and π-π interactions. Furthermore, MWSHC@CS showed excellent reusability for the removal of MG over five cycles of adsorption-desorption (83.76 %). In conclusion, the study provides a new, low-cost, and effective magnetic nanocomposite based on chitosan as a promising adsorbent for the high-performance removal of MG dye from aqueous solutions.

Co-Carbonized Waste Polythene/Sugarcane Bagasse Nanocomposite for Aqueous Environmental Remediation Applications.

The conversion of worthless municipal solid wastes to valuables is a major step towards environmental conservation and sustainability. This work successfully proposed a technique to utilize the two most commonly available municipal solid wastes viz polythene (PE) and sugarcane bagasse (SB) for water decolorization application. An SBPE composite material was developed and co-pyrolyzed under an inert atmosphere to develop the activated SBPEAC composite. Both SBPE and SBPEAC composites were characterized to analyze their morphological characteristics, specific surface area, chemical functional groups, and elemental composition. The adsorption efficacies of the composites were comparatively tested in the removal of malachite green (MG) from water. The SBPEAC composite had a specific surface area of 284.5 m2/g and a pore size of ~1.33 nm. Batch-scale experiments revealed that the SBPEAC composite performed better toward MG adsorption compared to the SBPE composite. The maximum MG uptakes at 318 K on SBPEAC and SBPE were 926.6 and 375.6 mg/g, respectively. The adsorption of MG on both composites was endothermic. The isotherm and kinetic modeling data for MG adsorption on SBPEAC was fitted to pseudo-second-order kinetic and Langmuir isotherm models, while Elovich kinetic and D-R isotherm models were better fitted for MG adsorption on SBPE. Mechanistically, the MG adsorption on both SBPE and SBPEAC composites involved electrostatic interaction, H-bonding, and π-π/n-π interactions.

Chitin-Based Magnesium Oxide Biocomposite for the Removal of Methyl Orange from Water.

In this work, a cost-effective chitin-based magnesium oxide (CHt@MgO) biocomposite with excellent anionic methyl orange (MO) dye removal efficiency from water was developed. The CHt@MgO biocomposite was characterized by FT-IR, XRD, SEM-EDX, and TGA/DTG. Results proved the successful synthesis of CHt@MgO biocomposite. Adsorption of MO on the CHt@MgO biocomposite was optimized by varying experimental conditions such as pH, amount of adsorbent (m), contact time (t), temperature (T), and initial MO concentration (Co). The optimized parameters for MO removal by CHt@MgO biocomposite were as follows: pH, 6; m, 2 g/L; t, 120 min. Two common isotherm models (Langmuir and Freundlich) and three kinetic models (pseudo-first-order (PFO), pseudo-second-order (PSO), and intraparticle diffusion (IPD)) were tested for experimental data fitting. Results showed that Langmuir and PFO were the most suitable to respectively describe equilibrium and kinetic results on the adsorption of MO adsorption on CHt@MgO biocomposite. The maximum Langmuir monolayer adsorption capacity (qm) on CHt@MgO biocomposite toward MO dye was 252 mg/g at 60 °C. The reusability tests revealed that CHt@MgO biocomposite possessed high (90.7%) removal efficiency after the fifth regeneration cycle.

Oral administration of a potassium bromate dosage: Determination and evaluation of accumulated bromate on the liver of male mice.

In this work, we developed a simple spectrophotometric strategy for BrO3- ions determination as a major water disinfection constituents in the mice's liver tissues by using pararosaniline (PRA). Mice were divided into seven main groups (6 doses): lowest dose KBrO3 (G1 0.01 mg L-1, G2 0.025 mg L-1 and G3 0.1 mg L-1), highest dose KBrO3 (G4 1 mg L-1, G5 10 mg·L-1 and G6 30 mg L-1) and control. All these groups maintained a dose-specific feeding for one month, just before the bromate assessment in mice's liver samples. The results revealed that groups of exposure to lower doses of drinking water did not detect the presence of BrO3- accumulated in the liver tissue during the study period (1-2 months). While, the BrO3- was detected in higher dosages for samples analyzed in first, second, third, fourth and fifth weeks (W1, W2, W3, W4, and W5). These results confirmed that the higher BrO3- dosages (1, 10, and 30 mg L-1) were fatal if introduced in drinking water and could accumulate in the liver tissues both for mice and for human. Detection the accuracy of the method for recovery of bromate ions in liver samples (N = 5) was found to be more than 95%. Relative standard deviations (RSDs) were found to be less than 2.0% confirming the reproducibility of the assay technique.

Oil industry waste based non-magnetic and magnetic hydrochar to sequester potentially toxic post-transition metal ions from water.

Solid waste conversion to value-added products is a stepping stone towards sustainable environment. Herein, sesame oil cake (SOC), an oil industry waste was utilized as a precursor to develop hydrochar (HC) samples by varying reaction temperature (150-250 °C) and time span (2-8 h), chemically treated with 10% H2O2 to optimize a sample with maximum yield and Pb(II) adsorption. Highest yield (29.2 %) and Pb(II) (24.57 mg/g at Co: 15 mg/L) adsorption was observed on SOCHC@200 °C/6 h, magnetized (mSOCHC@200 °C/6 h) for comparative study. XRD displayed highly crystalline SOCHC@200 °C/6 h and amorphous mSOCHC@200 °C/6 h, both having a characteristic cellulose peak at 14.9°. mSOCHC@200 °C/6 h displayed superparamagnetic behavior with 11.2 emu/g saturation magnetization. IR spectra confirmed the development of samples rich in oxygen containing functionalities; an additional peak for iron oxides appeared at 586 cm-1 in mSOCHC@200°C/6 h spectrum. Four major peaks at 531.9, 399.9, 348.2 and 284.7 eV, assigned to O 1s, N 1s, Ca 2p and C 1s, respectively were observed during XPS analyses. An additional peak at 710.3 eV, ascribed to Fe 2p was observed in mSOCHC@200C/6 h XPS spectrum, while a peak at 143.2 eV for Pb 4f appeared in spectra of both Pb(II) saturated samples. pH dependent (maximum at ∼6.7), exothermic Pb(II) adsorption was found. About 50-70% (at Co: 25 mg/L) adsorption on both SOCHC@200 °C/6 h and mSOCHC@200 °C/6 h was accomplished in a minute, attaining equilibrium in 180 and 240 min, respectively. Error functions and superimposed qe, exp. and qe, cal. values supported Langmuir isotherm model applicability, with respective qm values of 304.9 and 361.7 mg/g at 25 °C for SOCHC@200 °C/6 h and mSOCHC@200 °C/6 h. Kinetic data was fitted to PSO model. Highest (between 92.2 and 88.9 %) amount of Pb(II) from SOCHC@200 °C/6 h and mSOCHC@200 °C/6 h was eluted by 0.01 M HCl.

Excellent adsorptive performance of a new nanocomposite for removal of toxic Pb(II) from aqueous environment: Adsorption mechanism and modeling analysis.

Herein, a novel nanocomposite (Fe3O4@TATS@ATA) was prepared and used for adsorptive removal of Pb(II) ions from aqueous environment. The magnetic nanocomposite (Fe3O4@TATS@ATA) was characterized using FTIR, TEM, SEM, EDX, element mapping analysis (EMA), TGA analysis, XRD patterns, VSM, BET analysis, XPS spectrum, and zeta potential. The FTIR study confirmed the modification of Fe3O4 nanoparticles with triaminetriethoxysilane and 2-aminoterephthalic acid while XPS analysis (with peaks at 283.6, 285.1, 286.3, 284.5.0, 288.4 eV) displayed the presence of CSi, CN, OCNH, CC/CC and OCO functional groups, respectively on Fe3O4@TATS@ATA. The BET surface area, average pore size, pore volume and magnetization saturation for Fe3O4@TATS@ATA were found to be 114 m2/g, 6.4 nm, 0.054 cm-3/g, and 22 emu/g, respectively. The adsorption isotherm data showed that Pb(II) adsorption onto Fe3O4@TATS@ATA fitted to Langmuir and Dubinin-Raduskevich isotherm model due to better R2 value which was greater than 0.9 and qm of Pb(II) was 205.2 mg/g at pH 5.7 in 150 min. Adsorption kinetics data displayed that Pb(II) adsorption onto Fe3O4@TATS@ATA was fitted to the pseudo-second-order and Elovich kinetic models. Thermodynamic outcomes exhibited the exothermic and spontaneous nature of adsorption. Results showed that Fe3O4@TATS@ATA nanocomposite was promising material for efficient removal of toxic Pb(II) from aqueous environment.

Heteroatom-doped magnetic hydrochar to remove post-transition and transition metals from water: Synthesis, characterization, and adsorption studies.

Efforts to improve water quality have led to the development of green and sustainable water treatment approaches. Herein, nitrogen-doped magnetized hydrochar (mSBHC-N) was synthesized, characterized, and used for the removal of post-transition and transition heavy metals, viz. Pb2+ and Cd2+ from aqueous environment. mSBHC-N was found to be mesoporous (BET surface area - 62.5 m2/g) and paramagnetic (saturation magnetization - 44 emu/g). Both, FT-IR (with peaks at 577, 1065, 1609 and 3440 cm-1 corresponding to Fe - O stretching vibrations, C - N stretching, N - H in-plane deformation and stretching) and XPS analyses (with peaks at 284.4, 400, 530, 710 eV due to C 1s, N 1s, O 1s, and Fe 2p) confirmed the presence of oxygen and nitrogen containing functional groups on mSBHC-N. The adsorption of Pb2+ and Cd2+ was governed by oxygen and nitrogen functionalities through electrostatic and co-ordination forces. 75-80% of Pb2+ and Cd2+ adsorption at Co: 25 mg/L, either from deionized water or humic acid solution was accomplished within 15 min. The data was fitted to pseudo-second-order kinetic and Langmuir isotherm models, with maximum monolayer adsorption capacities being 323 and 357 mg/g for Cd2+and Pb2+ at 318 K, respectively. Maximum Cd2+ (82.6%) and Pb2+ (78.7%) were eluted with 0.01 M HCl, simultaneously allowing minimum iron leaching (2.73%) from mSBHC-N. In conclusion, the study may provide a novel, economical, and clean route to utilize agro-waste, such as sugarcane bagasse (SB), for aquatic environment remediation.

Unary and binary adsorption studies of lead and malachite green onto a nanomagnetic copper ferrite/drumstick pod biomass composite.

Modern-day practices are the major contributors in water quality deterioration, consequently results in clean water scarcity. Herein, co-precipitation procedure was adopted to develop a nanomagnetic copper ferrite/drumstick pod biomass (CuFe2O4/DC) composite, which was characterized, and optimized to sequester malachite green (MG) and lead (Pb(II)) in unary and binary systems from aqueous environment. Mesoporous CuFe2O4/DC surface with 16.96 m2/g BET surface area and acid functionalities predominance was observed. Under the studied experimental conditions, MG adsorption on CuFe2O4/DC in unary system was comparatively higher than that of Pb(II). MG and Pb(II) equilibrium results were fitted to Langmuir isotherm model, their respective maximum monolayer adsorption capacities at 328 K being 952.4 and 921.1 mg/g. On the other hand, binary system (in presence of MG) fastened Pb(II) adsorption kinetics and increased its uptake capacity. Additionally, humic acid (HA) matrix enhanced Pb(II) adsorption kinetics. Recovery studies showed maximal MG and Pb(II) elution with C2H5OH and 0.1 mol/L HCl, respectively. An 82.7% drop in Pb(II) adsorption was found after the first regeneration cycle, while only 17.6% fall in MG adsorption was witnessed after five consecutive regeneration cycles. Hence, it could be concluded that CuFe2O4/DC is a cost-effective and promising adsorbent for an efficient and rapid removal of Pb(II) and MG from both unary and binary systems.

A simple solvent extraction and ultra-performance liquid chromatography-tandem mass spectrometric method for the identification and quantification of rhodamine B in commercial lip balm samples.

Rhodamine B is a synthetic dye used in many industries including cosmetics. Long-term contact may results neurotoxicity, genotoxicity and cancer. In the present work, a simple solvent extraction followed by rapid, sensitive and selective ultra-performance liquid chromatography-tandem mass spectrometric method has been proposed for the identification and quantification of rhodamine B in lip balm samples for the first time to our knowledge. The best extraction was achieved using organic solvent n-hexane followed by sonication, centrifugation and evaporation. The chromatographic separation was attained in <1 min with Acquity™ BEH C18 reversed phase column and a tandem mass spectrometer. The limit of detection (LOD), limit of quantification (LOQ), linearity, precisions and accuracy of the proposed method were determined. The LOD and LOQ were found to be 0.1 µg/kg and 0.4 µg/kg, respectively. The linearity (R2) was obtained (>0.999) when analyzing low to higher range of concentrations. The precisions with relative standard deviation (RSD%) values in terms of repeatability (<2%, n = 5) and reproducibility (<3%, n = 5) were achieved. The accuracy in terms of recovery was obtained between 93% and 98%. The optimized procedures have been applied for the identification and quantification of rhodamine B in commercial lip balm samples from various brands and origin, and the amounts were obtained from not detected to 70.44 µg/kg. The good quality conditions, negligible matrix influence and higher recovery values obtained throughout analysis have proved the suitability of the present method for the routine analysis of rhodamine B in lip balm samples. The achieved results could be used to approximate the application of rhodamine B from individuals either from Saudi Arabia or globally, and thus to improve the quality and safety of lip balm products.

Adsorptive performance of MOF nanocomposite for methylene blue and malachite green dyes: Kinetics, isotherm and mechanism.

In the present study, Fe3O4@AMCA-MIL-53(Al) nanocomposite was utilized for the adsorptive removal of highly toxic MB and MG dyes from aqueous environment. The batch adsorption tests were performed at different contact time, pH, Fe3O4@AMCA-MIL-53(Al) dose, initial concentration of dyes and temperature. The maximum adsorption capacity of MB and MG dyes onto of Fe3O4@AMCA-MIL-53(Al) using Langmuir equation was 1.02 and 0.90 m mol/g, respectively. The isotherm and kinetic studies revealed that adsorption data were well fitted to Langmuir isotherm and pseudo-first-order kinetics models. Various thermodynamic parameters were also calculated and interpreted. The positive and negative values of ΔH° and ΔG° indicated that the adsorption was endothermic and spontaneous, respectively. The adsorptive binding of MB and MG on Fe3O4@AMCA-MIL53(Al) nanocomposite was directed by carboxylate and amide groups through electrostatic interaction, π-π interaction and hydrogen bonding. The desorption of both dyes from Fe3O4@AMCA-MIL-53(Al) was also performed using mixed solution of 0.01 M HCl/ethanol. Thus, we conclude that the Fe3O4@AMCA-MIL-53(Al) was an outstanding material for the removal of dyes from aqueous environment.

Cetyltrimethylammonium bromide intercalated and branched polyhydroxystyrene functionalized montmorillonite clay to sequester cationic dyes.

Herein, Cetyltrimethyl ammonium bromide (CTAB) intercalated and branched polyhydroxystyrene (BPS) functionalized montmorillonite (MMT) nano-composite (BPS-CTAB-MMT) was developed, characterized, and its potential as an adsorbent was tested in sequestering cationic dyes viz. rhodamine B (RB), crystal violet (CV), and methylene blue (MB) from aqueous environment. N2 adsorption/desorption isotherm showed mesoporous BPS-CTAB-MMT surface with a BET surface area of 273.8 m2/g. The appearance of sharp spikes at 2855 and 2925 cm-1 (associated with symmetric and asymmetric tensions of C - H bonds) in infra-red spectrum of BPS-CTAB-MMT indicates successful intercalation of MMT with CTAB and functionalization with BPS. The observed crystallite size of BPS-CTAB-MMT was 66 nm. Comparatively greater weight loss for BPS-CTAB-MMT (11%) than MMT (9%) was observed during thermogravimetric analysis. The adsorption of dyes on BPS-CTAB-MMT was pH dependent with maximum uptake was observed in the pH range: 5-6. For initial dyes concentration (Co) range: 50-150 mg/L, the observed equilibration time for CV was 300 min, whereas for RB and MB the equilibration time varied between 300 and 360 min. Modeling investigations revealed the applicability of Sips isotherm and pseudo-second-order (PSO) kinetic models to dyes adsorption data. Sips maximum adsorption capacity (qs) values for RB, CV, and MB at 55 °C were 476.5, 438.7, and 432.7 mg/g, respectively. The adsorption of dyes on BPS-CTAB-MMT was thermodynamically favorable. Desorption studies showed 42.1% RB and 41.9% CV recovery with 0.1 M NaOH and CH3COCH3, respectively, while only traces of MB were recovered with tested eluents.

A rapid and sensitive evaluation of nitrite content in Saudi Arabian processed meat and poultry using a novel ultra performance liquid chromatography-mass spectrometry method.

Quantitative assessment of nitrite (NO2-) anion was performed using a newly developed high throughput ultra performance liquid chromatography-mass spectrometric (UPLC-MS) method. The nitrite determination with the proposed method using micellar mobile phase was unknown. Selected ion reaction mode using negative electrospray ionization was adopted for the identification and quantitative analysis of nitrite. The chromatographic separation was performed using BEH C-18 column and a micellar mobile phase consisted of sodium dodecyl sulphate and acetonitrile in ratio 30:70 was used. The elution of nitrite anion was accomplished in less than 1 min. Under the optimal analysis conditions, the linearity of the developed method was checked in the concentration range of 0.5-20 mg kg-1 NO2- with an excellent correlation coefficient of 0.996. The precisions of the method with relative standard deviation <2% was observed when standard at concentration of 1 mg kg-1 was used. The limit of detection and limit of quantitation of the developed mass spectrometric method was found to be 0.114 and 0.346 mg kg-1, respectively. The developed UPLC/MS method was applied to quantify this anion in processed meats and poultries from various super market of Saudi Arabia (Riyadh region). The recoveries of the nitrite in the various samples were found in the range of 100.03-103.5%.

Novel Metal-Organic Framework (MOF) Based Composite Material for the Sequestration of U(VI) and Th(IV) Metal Ions from Aqueous Environment.

The combination of magnetic nanoparticles and metal-organic frameworks (MOFs) has demonstrated their prospective for pollutant sequestration. In this work, a magnetic metal-organic framework nanocomposite (Fe3O4@AMCA-MIL53(Al) was prepared and used for the removal of U(VI) and Th(IV) metal ions from aqueous environment. Fe3O4@AMCA-MIL53(Al) nanocomposite was characterized by TGA, FTIR, SEM-EDX, XRD, HRTEM, BET, VSM (vibrating sample magnetometry), and XPS analyses. A batch technique was applied for the removal of the aforesaid metal ions using Fe3O4@AMCA-MIL53(Al) at different operating parameters. The isotherm and kinetic data were accurately described by the Langmuir and pseudo-second-order models. The adsorption capacity was calculated to be 227.3 and 285.7 mg/g for U(VI) and Th(IV), respectively, by fitting the equilibrium data to the Langmuir model. The kinetic studies demonstrated that the equilibrium time was 90 min for each metal ion. Various thermodynamic parameters were evaluated which indicated the endothermic and spontaneous nature of adsorption. The collected outcomes showed that Fe3O4@AMCA-MIL53(Al) was a good material for the exclusion of these metal ions from aqueous medium. The adsorbed metals were easily recovered by desorption in 0.01 M HCl. The excellent adsorption capacity and the response to the magnetic field made this novel material an auspicious candidate for environmental remediation technologies.

Mercerized mesoporous date pit activated carbon-A novel adsorbent to sequester potentially toxic divalent heavy metals from water.

A substantive approach converting waste date pits to mercerized mesoporous date pit activated carbon (DPAC) and utilizing it in the removal of Cd(II), Cu(II), Pb(II), and Zn(II) was reported. In general, rapid heavy metals adsorption kinetics for Co range: 25-100 mg/L was observed, accomplishing 77-97% adsorption within 15 min, finally, attaining equilibrium in 360 min. Linear and non-linear isotherm studies revealed Langmuir model applicability for Cd(II) and Pb(II) adsorption, while Freundlich model was fitted to Zn(II) and Cu(II) adsorption. Maximum monolayer adsorption capacities (qm) for Cd(II), Pb(II), Cu(II), and Zn(II) obtained by non-linear isotherm model at 298 K were 212.1, 133.5, 194.4, and 111 mg/g, respectively. Kinetics modeling parameters showed the applicability of pseudo-second-order model. The activation energy (Ea) magnitude revealed physical nature of adsorption. Maximum elution of Cu(II) (81.6%), Zn(II) (70.1%), Pb(II) (96%), and Cd(II) (78.2%) were observed with 0.1 M HCl. Thermogravimetric analysis of DPAC showed a total weight loss (in two-stages) of 28.3%. Infra-red spectral analysis showed the presence of carboxyl and hydroxyl groups over DPAC surface. The peaks at 820, 825, 845 and 885 cm-1 attributed to Zn-O, Pb-O, Cd-O, and Cu-O appeared on heavy metals saturated DPAC, confirmed their binding on DPAC during the adsorption.

Determination of heavy metals in skin-whitening cosmetics using microwave digestion and inductively coupled plasma atomic emission spectrometry.

In this study, the determination of noxious heavy metals, cadmium (Cd), bismuth (Bi), mercury (Hg), titanium (Ti), lead (Pb) and metalloid arsenic (As) in skin-whitening cosmetics were examined using microwave digestion and inductively coupled plasma atomic emission spectrometry method. A complete digestion of cosmetics samples was achieved using a mixture of hydrofluoric acid/hydrogen peroxide/nitric acid. The quantification of the target compounds was done by standard addition method. The excellent quality parameters for instance, detection limits, As (4.6 ppb), Bi (7.9 ppb), Cd (0.45 ppb), Hg (3.3 ppb), Pb (3.8 ppb), Ti (4.3 ppb), linearity (r2 > 0.999) and run-to-run and day-to-day precisions with relative standard deviations <3% were obtained. The recovery rates for standard reference materials were found between 90 and 105%. The average concentration of heavy metals in cosmetics samples were in the range of 1.0-12.3 (µg g-1, As), 33-7097 (µg g-1, Bi), 0.20-0.6 (µg g-1, Cd), 0.70-2700 (µg g-1, Hg), 1.20-143 (µg g-1, Pb) and 2.0-1650 (µg g-1, Ti).