Recycling of Date Pits Into a Green Adsorbent for Removal of Heavy Metals: A Fractional Factorial Design-Based Approach

Date pits (DPs) have been recycled into a low-cost adsorbent for removing of selected heavy metals (HMs) from artificially contaminated aqueous solutions. Adsorption of targeted HMs, both by raw date pits (RDP) and burnt date pits (BDP) was tested. Results showed that BDP is more efficient as an adsorbent and mostly adsorbing Cu(II). A novel approach; fractional factorial design (2k−p – FrFD) was used to build the experimental pattern of this study. The effects of four factors on the maximum percentage (%) of removal (Y) were considered; pH, adsorbent dose (AD), heavy metal concentration (HMC), and contact time (CT). Statistically significant variables were detected using Pareto chart of standardized effects, normal and half-normal plots together with analysis of variance (ANOVA) at 95.0 confidence intervals (CI). Optimizing (maximizing) the percentage (%) removal of Cu(II) by BDP, was performed using optimization plots. Results showed that the factors: pH and adsorbent dose (AD) affect the response positively. Scanning electron microscopy (SEM) was used to study the surface morphology of both adsorbents while fourier-transform infrared spectroscopy (FTIR) was employed to get an idea on the functional groups on the surface and hence the adsorption mechanism. Raman spectroscopy was used to characterize the prepared adsorbents before and after adsorption of Cu(II). Equilibrium studies show that the adsorption behavior differs according to the equilibrium concentration. In general, it follows Langmuir isotherm up to 155 ppm, then Freundlich isotherm. Free energy of adsorption (ΔGad) is −28.07 kJ/mole, when equilibrium concentration is below 155 ppm, so the adsorption process is spontaneous, while (ΔGad) equals +17.89 kJ/mole above 155 ppm, implying that the process is non-spontaneous. Furthermore, the adsorption process is a mixture of physisorption and chemisorption processes, which could be endothermic or exothermic reactions. The adsorption kinetics were described using a second order model.Funding. This work was made possible by UREP award [UREP 20-116-1-020] from the Qatar National Research Fund (a member of The Qatar Foundation). The statements made herein are solely the responsibility of the authors

Antibiotics in hospital effluent and domestic wastewater treatment plants in Doha, Qatar

Wastewater samples were collected from the main hospital’s effluent (HWW), influents and effluents of the old wastewater treatment plant (OWWTP) built in 1990 and the new one (NWWTP) built in 2010 located in Doha, Qatar. Analytical methods were optimized to determine the concentrations of eight selected antibiotics (ABs): penicillin, amoxicillin, gentamicin, ciprofloxacin, tetracycline, erythromycin, metronidazole, and clavulanic acid. Samples were prepared through automated solid phase extraction (SPE) before analysis using liquid chromatography - mass spectrometry (LC–MS) with positive ion electrospray. Among the eight target compounds tested, recoveries were obtained in the range of 47.5–98%. The highest concentration of metronidazole and ciprofloxacin were detected in the HWW at levels of 5.46 μg/L and 1.99 μg/L, respectively. In effluents samples collected from both WWTPs, clavulanic acid was the most prominent compound at concentration of 84.74 μg/L. The highest concentration of erythromycin (7.20 μg/L) was detected in the influent sample collected from OWWTP. Amoxicillin, penicillin, and erythromycin were below the detection limit (0.1 μg/L). There was a significant statistical correlation between the concentrations of most of the studied antibiotics. Ciprofloxacin was highly correlated with erythromycin, clavulanic acid, and metronidazole in all influent samples, whereas the concentration of erythromycin was highly correlated with those of amoxicillin, ciprofloxacin, tetracycline and penicillin in all effluent samples. No significant difference (P ≥ 0.05) was found between concentrations of the targeted antibiotics in the NWWTP and OWWTP. Generally, both treatment plants showed effective removal rates (99.44%) of penicillin and metronidazole. However, clavulanic acid and ciprofloxacin were not removed from the effluent of either plant, even though the effluent passed through the ultrafiltration stage in the new WWTP. The findings reveal that HWW is not the only source of ABs in wastewater but direct disposal onto the sewer system could be the major source. The study calls for further investigation of additional pharmaceuticals and other emerging contaminants in the wastewater of Qatar as well as their metabolites and biodegradation products as well as application of advanced treatment technologies for highest removal rate and safe water reuse options.We thank Dr. Muhammad Al-Sayrafi, Thomas Michael, Haira Binti Mokhtar, Noor Al-Motawa, Dr. Hany Hussein, Dr. Mohammad Al-Ghouti, Munshi Masudul Haq, and Dr. Mohammed Abu-Dieyeh for various assistances on the project. This study was made possible by a grant from Qatar University Office of Academic Research ( QUST-CAS-FALL-14/15-30 ).Scopu

Pomegranate peels as versatile adsorbents for water purification: Application of box–behnken design as a methodological optimization approach

Pomegranate peels (PGP) were tested as a green adsorbent for the removal of Ni(II) from contaminated water samples. Both raw (RPG), and char/burnt peels (BPG) were tested. A multivariate analysis approach, Box–Behnken (BB) design was executed to augment the efficiency of BPG as adsorbent. Three factors were considered thereof; contact time (CT), adsorbent dose (AD), and heavy metal concentration (HMC). The percentage of heavy metal removal was the designated response (Y). Main effects plot together with analysis of variance (ANOVA) were used to decide on the substantial factors. Obtained results showed that AD was the most significant linear factor, while the interaction between AD*HMC was the most influential two‐way interaction. Contour and response surface plots were used to study the factorial interactions and optimize the response. Desirability function was used to find the best factorial combination for maximum removal of Ni(II). Efficacies of both adsorbents were compared and BPG was more effectual achieving 99.99% removal of Ni(II). Surface morphology was characterized using FTIR, BET, SEM, and EDX analyses. Results indicated that functional groups such as hydroxyl, amino, carboxylic acid are available on surface of PGP and might be responsible for the adsorption process. © 2019 American Institute of Chemical Engineers Environ Prog, 38: e13223, 2019This work was made possible by UREP award [UREP 20-116-1-020] from the Qatar National Research Fund (a member of The Qatar Foundation). The statements made herein are solely the responsibility of the authors.Scopu

Smart synthesis of trimethyl ethoxysilane (TMS) functionalized core?shell magnetic nanosorbents Fe3O4@SiO2: Process optimization and application for extraction of pesticides

In the current study, a smart approach for synthesizing trimethyl ethoxysilane?decorated magnetic-core silica-nanoparticles (TMS-mcSNPs) and its effectiveness as nanosorbents have been exploited. While the magnetite core was synthesized using the modified M�ssbauer method, St�ber method was employed to coat the magnetic particles. The objective of this work is to maximize the magnetic properties and to minimize both particle size (PS) and particle size distribution (PSD). Using a full factorial design (2k-FFD), the influences of four factors on the coating process was assessed by optimizing the three responses (magnetic properties, PS, and PSD). These four factors were: (1) concentration of tetraethyl-orthosilicate (TEOS); (2) concentration of ammonia; (3) dose of magnetite (Fe3O4); and (4) addition mode. Magnetic properties were calculated as the attraction weight. Scanning electron microscopy (SEM) was used to determine PS, and standard deviation (�SD) was calculated to determine the PSD. Composite desirability function (D) was used to consolidate the multiple responses into a single performance characteristic. Pareto chart of standardized effects together with analysis of variance (ANOVA) at 95.0 confidence interval (CI) were used to determine statistically significant variable(s). Trimethyl ethoxysilane?functionalized mcSNPs were further applied as nanosorbents for magnetic solid phase extraction (TMS-MSPE) of organophosphorus and carbamate pesticides.Scopu