Hazardous Materials

Removal of Cr3+ from tanning effluents by adsorption onto phosphate mine waste: Key parameters and mechanisms Publication date: 15 October 2019 Source: Journal of Hazardous Materials, Volume 378 Author(s): Amal Oumani, Laila Mandi, Fatima Berrekhis, Naaila Ouazzani Abstract The present study aims to investigate key parameters and mechanisms affecting Cr3+ removal from tanning wastewater using phosphate mine waste (PW) as adsorbent in batch mode. The initial Cr3+ concentration was 3920 mg.L−1. The maximum removal capacity of Cr3+ was found to be 97.23 mg.g−1 using 40 g.L−1 of PW at 50 °C and at 200 rpm of stirring speed. Thermodynamic studies indicated that Cr3+ sorption is endothermic reaction of a physico-chemical adsorption process. Kinetic data were satisfactorily described by a pseudo-second order model. Cr3+ removal is probably involving several mechanisms: PW surface dissolution, precipitation, co-precipitation, ion exchange and adsorption. The chromium sorption seems modifying the crystalline structure of the adsorbent. Adsorption isotherm was described by Freundlich, Langmuir and Redlich-Peterson models. But statistically, Freundlich fit better the experimental data. Five error functions were used to check this result. Treatment of chromium effluent using PW as adsorbent can also eliminate more than 60% of organic matter and then can be considered as an effective biomaterial for tanning wastewater treatment.

Experimental study on explosion characteristics of ethanol gasoline–air mixture and its mitigation using heptafluoropropane Publication date: 15 October 2019 Source: Journal of Hazardous Materials, Volume 378 Author(s): Guochun Li, Xishi Wang, Hongli Xu, Yangpeng Liu, Heping Zhang Abstract Ethanol gasoline is being widely used as a new environmentally friendly and energy-saving alternative energy, and the control/reduction of its fire/explosion risk has become an important aspect, not only for its production and storage, but also for its transport and application. This study aims to investigate the explosion characteristics of ethanol gasoline and its mitigation using heptafluoropropane in a restricted vessel. The flame propagation was visualized using a Phantom high-speed camera at 3000 fps, the explosion overpressure was measured using PCB pressure sensors, and the gas released from the vent was collected and analyzed using a gas chromatography-mass spectrometer. The results indicate that heptafluoropropane has a good suppression effect on the flame propagation speed and the explosion overpressure. The maximum overpressure of an ethanol gasoline explosion is approximately 456 kPa, and the overpressure reduction exceeds 60% when the concentration of heptafluoropropane addition is 10%, whereas an explosion is completely mitigated when the concentration of heptafluoropropane continuously increases. In addition, different flame colors during the mitigation process, such as blue, yellow, and purple, were observed and analyzed. The results of this study will be valuable for further understanding ethanol gasoline explosion mitigation and designing optimum heptafluoropropane explosion mitigation systems. Graphical abstract

Interaction with low molecular weight organic acids affects the electron shuttling of biochar for Cr(VI) reduction Publication date: 15 October 2019 Source: Journal of Hazardous Materials, Volume 378 Author(s): Zibo Xu, Xiaoyun Xu, Xinyi Tao, Chengbo Yao, Daniel C.W. Tsang, Xinde Cao Abstract Biochar can act as "electron shuttle" in soil redox reactions. It is possible that biochar accepts the electrons from low molecular weight organic acids (LMWOAs) in soil and then transfer them to the acceptors, e.g., Cr(VI). This study evaluated the interaction between seven soil LMWOAs and peanut shell biochar (BC) as well as its effect on the electron shuttling of biochar for Cr(VI) reduction. Both redox reactions and sorption process occurred during the interaction of biochar and LMWOAs, which altered the contents of Cr(VI) reduction-relevant groups (i.e., CO and CO) on the surface of biochar. The redox reactions were more important to the electron transfer between biochar produced at 400℃ (BC400) and LMWOAs due to the repeated cycle of reduction-oxidation of surface functional groups. The reduction rate of Cr(VI) by LMWOAs mediated by BC400 was 1.10–7.09 × 10−3 h-1, among which tartaric acid had the best reduction efficiency due to its highest reducing capability. For biochar produced at 700℃ (BC700), the sorption process of LMWOAs was the key factor to the direct electron shuttling process through the conjugated structure of biochar. The reduction rate of Cr(VI) by LMWOAs mediated by BC700 was significantly higher and ranged 7.40–864 × 10−3 h-1, with the oxalic acid having the best reduction efficiency due to its highest sorption capacity by BC700. The results obtained from this study can help to establish the linkage between biochar and LMWOAs in soil electron network, which better explains the multifunctional roles of biochar during the redox processes such as Cr(VI) reduction in soil. Graphical abstract

Preparation and characterization of styrene-butadiene-styrene membrane incorporated with graphene nanosheets for pervaporative removal of 1,2,4-trimethylbenzene from water Publication date: 15 October 2019 Source: Journal of Hazardous Materials, Volume 378 Author(s): S.A. Mousavinezhad, S.M. Mousavi, E. Saljoughi Abstract In the present study, novel styrene-butadiene-styrene (SBS) membranes were prepared by the addition of graphene (Gr) nanosheets to the casting solution and were utilized in the pervaporative separation of a dilute solution of 1,2,4-trimethylbenzene (1,2,4-TMB) as a volatile organic compound (VOC) in water. Several characterizations such as field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), mechanical tensile test, and determination of water contact angle and swelling degree were conducted to investigate the properties of the prepared membranes. The results showed that with the addition of Gr the membrane thermal stability and hydrophobicity were increased while there was an optimum Gr loading to achieve the highest elastic modulus and tensile strength. Moreover, it was found that by increasing the Gr concentration up to 0.5 wt. %, the separation factor and pervaporation separation index (PSI) were increased by 250% and 43% compared to pure SBS membrane and reached 930 and 545 kg/m2h, respectively.

Activation of fulvic acid-like in paper mill effluents using H2O2/TiO2 catalytic oxidation: Characterization and salt stress bioassays Publication date: 15 October 2019 Source: Journal of Hazardous Materials, Volume 378 Author(s): Yuanyuan Yao, Chun Wang, Xiaoqi Wang, Yuechao Yang, Yongshan Wan, Jianqiu Chen, Fangjun Ding, Yafu Tang, Zhonghua Wang, Lu Liu, JiaZhuo Xie, Bin Gao, Yuncong C. Li, Gilbert C. Sigua Abstract Increasing environmental concerns about organic waste in paper mill effluents demand alternative wastewater management technology. We reported novel activation of fulvic acid-like in paper mill effluents using hydrogen peroxide (H2O2) as oxidizer and titanium oxide (TiO2) as catalyst. Spectroscopic characteristics of fulvic acid-like in paper mill effluents before and after activation (PFA and PFA-Os, respectively) were compared with a benchmark fulvic acid extracted from leonardite (LFA). Results indicated that PFA-Os exhibited less lignin structures, more functional groups and lower molecular weight than PFA, sharing much similarity with LFA. Among PFA-Os with varying degrees of oxidation, PFA-O-3 activated with 1:2 vol ratio of paper mill effluent and 30% H2O2 for 20 min digestion at 90 °C stands out to be the optimal for further examination of its biological activity. Bioassays with rice seed/seedling indicated that applications of LFA at 2–5 mg-C/L and PFA-O-3 at 60–100 mg-C/L significantly increased rice seed germination rate and seedling growth under salt stress imposed with 100 mM NaCl. The mechanism was mainly through reduced oxidative damage via activation of antioxidative enzymes and lipid peroxidation. This study provides the needed technical basis of safer and cleaner technologies for innovative management of paper mill effluents. Graphical abstract

Tuning ignition and energy release properties of Zirconium powder by atomic layer deposited metal oxide coatings Publication date: 15 October 2019 Source: Journal of Hazardous Materials, Volume 378 Author(s): Lijun Qin, Ting Gong, Jianguo Li, Ning Yan, Longfei Hui, Hao Feng Abstract Ultra-fine powders of reactive metals are promising fuels/additives for propellants. However, the metal surfaces make these materials very unstable in ambient atmosphere. This study explored the method of applying thin films of inorganic materials onto the surface of Zr powder and investigated the effects of different surface coatings on the energy release and ignition process of Zr. Thin films of Al2O3 and ZnO were deposited on a commercial micron-scale Zr powder by atomic layer deposition (ALD). Growth kinetics of ALD films on the Zr particles were studied using various tools. Chemical and structural characterizations revealed that the Zr particles were completely encapsulated by uniform Al2O3 or ZnO films. The thicknesses of the encapsulation layers could be precisely controlled. ALD Al2O3 coatings exhibited a unique surface-sealing effect, which inhibited the low temperature oxidation of Zr in ambient air. Laser and electrostatic discharge (ESD) ignition tests revealed that ALD Al2O3 coatings extended the ignition delay and reduced the ESD sensitivity of the Zr powder. In comparison, ALD ZnO coatings could not form effective gas diffusion barriers, therefore they could not change the oxidation process of Zr and only showed modest effects on ignition and ESD sensitivity of the Zr powder. Graphical abstract

Petroleum-contaminated sites: Decision framework for selecting remediation technologies Publication date: 15 October 2019 Source: Journal of Hazardous Materials, Volume 378 Author(s): Brício Marcelino da Silva, Leila Teresinha Maranho

The application of machine learning methods for prediction of metal sorption onto biochars Publication date: 15 October 2019 Source: Journal of Hazardous Materials, Volume 378 Author(s): Xinzhe Zhu, Xiaonan Wang, Yong Sik Ok Abstract The adsorption of six heavy metals (lead, cadmium, nickel, arsenic, copper, and zinc) on 44 biochars were modeled using artificial neural network (ANN) and random forest (RF) based on 353 dataset of adsorption experiments from literatures. The regression models were trained and optimized to predict the adsorption capacity according to biochar characteristics, metal sources, environmental conditions (e.g. temperature and pH), and the initial concentration ratio of metals to biochars. The RF model showed better accuracy and predictive performance for adsorption efficiency (R2 = 0.973) than ANN model (R2 = 0.948). The biochar characteristics were most significant for adsorption efficiency, in which the contribution of cation exchange capacity (CEC) and pHH2O of biochars accounted for 66% in the biochar characteristics. However, surface area of the biochars provided only 2% of adsorption efficiency. Meanwhile, the models developed by RF had better generalization ability than ANN model. The accurate predicted ability of developed models could significantly reduce experiment workload such as predicting the removal efficiency of biochars for target metal according to biochar characteristics, so as to select more efficient biochar without increasing experimental times. The relative importance of variables could provide a right direction for better treatments of heavy metals in the real water and wastewater. Graphical abstract

Sequential biowashing-biopile processes for remediation of crude oil contaminated soil in Kuwait Publication date: 15 October 2019 Source: Journal of Hazardous Materials, Volume 378 Author(s): Taein Kim, Jin-Kyung Hong, Eun Hea Jho, Guyoung Kang, Dong Jin Yang, Sung-Jong Lee Abstract The application of biological processes for remediation of the aged crude oil-contaminated soil of Kuwait can be an inefficient way, thus, this study developed 20 d-sequential biowashing and biopile processes where the biowashing step uses an enrichment culture of the indigenous soil bacterial community and the biopile step includes hemoglobin-catalyzed oxidation (HCO). The residual total petroleum hydrocarbons (TPH) concentrations and CO2 generation were measured to determine the removal efficiency, and the bacterial community changes were studied to investigate the effect of the sequential processes on the soil indigenous bacterial community. The enrichment culture grown on hemoglobin showed an increased surface activity, and this promoted desorption and emulsification of crude oil from the soil sample in the biowashing step resulting in 75% TPH removal. Potential surfactant-producing bacterial species were observed in the soil sample after biowashing. The HCO in the beginning of the biopile step removed 21% of the residual TPH, and further TPH removal was observed with a longer biopile period. Overall, the sequential biowashing and biopile processes removed 86% TPH. The results show that the developed sequential biowashing and biopile processes can be used to efficiently remediate the aged crude oil-contaminated soil of Kuwait.

Development of a magnetic core-shell Fe3O4@TA@UiO-66 microsphere for removal of arsenic(III) and antimony(III) from aqueous solution Publication date: 15 October 2019 Source: Journal of Hazardous Materials, Volume 378 Author(s): Pengfei Qi, Rong Luo, Thomas Pichler, Jianqiang Zeng, Yan Wang, Yuhua Fan, Kunyan Sui Abstract Removal of trivalent species of As and Sb from wastewater is crucial due to their more toxic and mobile properties. In this study, a novel magnetic core-shell microsphere Fe3O4@TA@UiO-66 was developed via in-situ crystal growth of UiO-66 around the magnetic Fe3O4 modified by Tannic Acid (TA). Characterization of the microsphere by transmission electron microscopy (TEM) and X-ray diffraction spectroscopy (XRD) confirmed that UiO-66 was adhered on the surface of Fe3O4 functionalized by TA. Adsorption experiments showed that the magnetic Fe3O4@TA@UiO-66 had high adsorption capacity for As(III) and Sb(III) and could be rapidly separated from aqueous media within two minutes after treatment. The adsorption kinetics and adsorption isotherms were described well by the pesudo-second order model and Langmuir model, respectively. In addition, the composite exhibited excellent removal performance for As(III) and Sb(III) in a broad solution chemistry environment, including pH and co-existing anions. Based on X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) measurement, we proposed that the removal mechanism was mainly controlled through a synergistic interaction of surface complexation and hydrogen bonding. This study indicates the potential of the magnetic microsphere to be used as an effective material for the removal of As(III) and Sb(III) from water. Graphical abstract

Alexandros Sfakianakis
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alsfakia@gmail.com