This study presents the modification of cassava root husk-derived biochar (CRHB) with ZnO nanoparticles (ZnO-NPs) for the simultaneous adsorption of As(
iii
), Cd(
ii
), Pb(
ii
) and Cr(
vi
). By ...conducting batch-mode experiments, it was concluded that 3% w/w was the best impregnation ratio for the modification of CRHB using ZnO-NPs, and was denoted as CRHB-ZnO3 in this study. The optimal conditions for heavy metal adsorption were obtained at a pH of 6-7, contact time of 60 min, and initial metal concentration of 80 mg L
−1
. The heavy metal adsorption capacities onto CRHB-ZnO3 showed the following tendency: Pb(
ii
) > Cd(
ii
) > As(
iii
) > Cr(
vi
). The total optimal adsorption capacity achieved in the adsorption of the 4 abovementioned metals reached 115.11 and 154.21 mg g
−1
for CRHB and CRHB-ZnO3, respectively. For each Pb(
ii
), Cd(
ii
), As(
iii
), and Cr(
vi
) metal, the maximum adsorption capacities of CRHB-ZnO3 were 44.27, 42.05, 39.52, and 28.37 mg g
−1
, respectively, and those of CRHB were 34.47, 32.33, 26.42 and 21.89 mg g
−1
, respectively. In terms of kinetics, both the pseudo-first-order and the pseudo-second-order fit well with metal adsorption onto biochars with a high correlation coefficient of
R
2
, while the best isothermal description followed the Langmuir model. As a result, the adsorption process of heavy metals onto biochars was chemisorption on homogeneous monolayers, which was mainly controlled by cation exchange and surface precipitation mechanisms due to enriched oxygen-containing surface groups with ZnO-NP modification of biochar. The FTIR and EDS analysis data confirmed the important role of oxygen-containing surface groups, which significantly contributed to removal of heavy metals with extremely high adsorption capacities, comparable with other studies. In conclusion, due to very high adsorption capacities for metal cations, the cassava root husk-derived biochar modified with ZnO-NPs can be applied as the alternative, inexpensive, non-toxic and highly effective adsorbent in the removal of various toxic cations.
This study presents the modification of cassava root husk-derived biochar (CRHB) with ZnO nanoparticles (ZnO-NPs) for the simultaneous adsorption of As(
iii
), Cd(
ii
), Pb(
ii
) and Cr(
vi
).
In this study, chicken manure biochar (CBC) was prepared and applied as adsorbent for the removal of phenolic pollutants including phenol (Ph) and 2,4-Dinitrophenol (DNP) from wastewaters. The ...feasibility analysis was focused on the adsorption effects of various factors, such as initial concentration, adsorbent dosage and reaction time. The results showed that BC could efficiently remove the Ph and DNP within 90 min of reaction time. Increasing of CBC dosage up to 0.3 g results in the maximum removal efficiency of Ph and DNP and lowers initial concentration which is beneficial for the adsorption of phenolic compounds. The second-order kinetic model and the Langmuir isotherm provided the best correlation with the adsorption data. Based on the Langmuir isotherm, maximum adsorption capacities (qmax) of Ph and DNP were found at 106.2 and 148.1 mg g−1, respectively. The obtained qmax values for CB were higher than those reported in literature on the adsorption of Ph and DNP using different biochar. Analyzing the regeneration characteristics, BC displayed high reusability with less than 20% loss in adsorption capacities of Ph and DNP, even after five repeated cycles. Investigation of the adsorption equilibrium under various conditions suggested several possible interaction mechanisms, including hydrogen bonding, electrostatic interaction and π- π bonding, which were attributed to the binding affinity of the adsorbent-adsorbate interaction.
In the field application, the CBC showed an excellent removal efficiencies of Ph and DNP from industrial wastewaters (around 80% phenolic pollutants were removed). These findings support the potential use of CBC as effective adsorbent for treatment of wastewater containing Ph and DNP.
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•Chicken manure biochar is an effective adsorbent for the removal of phenolic compounds.•Adsorption capacities of phenol and 2, 4-dinitrophenol were 106.2 and 148.1 mg g−1, respectively.•Removal efficiencies of phenol and 2, 4-dinitrophenol in wastewater were 78.5 and 83.4%, respectively.•Chicken manure biochar showed high reuse ability even after 5 times reused.
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•Cu doped TiO2 was synthesized to enhanced the photocatalytic water splitting.•Cu doped TiO2 exhibited excellent visible-light photocatalytic H2 generation (45.6 mmol/h)•Cu-TiO2 can ...reused five times without the loss of H2 production capacity.•Cu-TiO2-based photocatalyst has potential to apply for sustainable H2 production.
Titanium dioxide (TiO2) based materials were used in many fields such as energy application, biological and environment remediation control. In this study, copper-doped TiO2 (Cu-TiO2) was synthesized and investigated for photocatalytic water splitting hydrogen (H2) evolution. The doping of Cu ions not only increased the oxygen vacancies but also improved the charge separation of photocatalyst. The Cu-TiO2 displayed a higher the rate of H2 evolution (45.6 mmol/h) as compared to undoped TiO2 (0.73 mmol/h). The reused of material was identified and the photocatalytic water splitting mechanism of Cu-TiO2 was proposed. The results showed that, Cu-TiO2 had high stability after reusing for 5 consecutive cycles without the loss of H2 production capacity. In addition, practical application and future research were discussed in details. This work may contribute to the potential application of TiO2-based photocatalyst for water splitting in order to produce H2 gas as green energy.
In this study, we investigated the feasibility on the utilization of coffee husk as biosorbents for the removal of heavy metal ions such as Pb2+ and Cd2+ from wastewater. Biochar was produced from ...coffee wastes and modified with sodium hydroxide to create functional groups on the surface and increase the specificic surface area. The resultant products were characterized by using various analytical methods such as scanning electron microscopy, specific area, surface functional group and zeta potential analysis. The as-prepared materials were employed as adsorbent to remove Pb2+ and Cd2+ ions from wastewater. The maximum sorption capacities of biosorbents were measured to be 116.3 and 139.5 mg g−1 for Cd2+ and Pb2+, respectively, which is comparable to the conventional adsorbents. Kinetic studies showed that the sorption of Pb2+ and Cd2+ on biosorbents can be described by the Freundlich isotherm and second-order kinetic model. The coffee husk-derived biosorbent was capable of removing 89.6% of Pb2+ and 81.5% Cd2+ ions from wastewater, and therefore can be considered as low-cost and efficient adsorbent to remove heavy metal ions from wastewater.
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•Low-cost biosorbent was prepared from coffee husk biomass for removal of heavy metals.•Maximum adsorption capacities of Cd and Pb were 116.3 and 139.5 mg g−1, respectively.•81.5% of Cd and 89.6% of Pb was removed from wastewater by using coffee biochar.
Atmospheric halogenated polycyclic aromatic hydrocarbons (Halo-PAHs) and parent PAHs were monitored in Ulsan, South Korea for one year (January‒December 2015) to investigate their seasonal patterns, ...gas/particle partitioning behavior, and the impact of meteorological conditions. The mean concentrations of 24 chlorinated PAHs, 11 brominated PAHs, and 13 parent PAHs in the gaseous and particulate phases were 8.64 and 9.64 pg/m3, 11.6 and 1.62 pg/m3, and 2.17 and 2.40 ng/m3, respectively. Winter had the highest ClPAH and PAH levels, with significant contributions from poly-chlorine groups and high-molecular-weight compounds. However, BrPAHs showed reverse patterns with the highest concentration in summer and the dominant gaseous fraction throughout the year. This finding could be explained by the strong local sources of BrPAHs, related to automobile and petrochemical industries. In contrast, the effects of the temperature inversion layer and atmospheric transport from the outside of Ulsan were more apparent for ClPAHs and PAHs, particularly in winter and spring. Regarding gas/particle partitioning, Halo-PAHs exhibited different seasonal behaviors from those of parent PAHs. The sorption pathway of Halo-PAHs seemed to shift from absorption as the sole dominant mechanism in winter and spring to both adsorption and absorption in summer and fall, while both partitioning mechanisms contributed equally for parent PAHs during the entire year. This study implies that Halo-PAHs and parent PAHs might not share the same atmospheric behavior, possibly due to different characteristics in atmospheric reactions with other chemicals and particle-size distribution. However, there have been limited studies about the formation of Halo-PAHs and their physicochemical properties; hence, further in-depth investigations are of vital importance.
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•Winter had the highest ClPAH and PAH levels with significant contributions of HMWs.•Gaseous BrPAHs reached the maximum concentration in summer due to local sources.•The influence of LRAT on ClPAHs and PAHs was more apparent than on BrPAHs.•TILs were more frequent in winter, leading to higher levels of ClPAHs and PAHs.•The gas/particle partitioning mechanisms for Halo-PAHs were seasonally different.
The Daesan industrial complex is one of the largest petrochemical and oil refinery industrial complexes in South Korea, which is believed to be a major source of polycyclic aromatic hydrocarbons ...(PAHs). Total suspended particle (TSP) samples (n = 84) were seasonally collected at two industrial sites and one residential site, and 19 PAHs were analyzed. Concentrations of individual PAHs ranged from 0.01 to 2.52 ng/m3, and annual mean concentrations of Σ19 PAHs at Sites 1, 2, and 3 were 5.88, 4.52, and 5.08 ng/m3, respectively. The concentrations of Σ19 PAHs in warm seasons (spring and summer) were lower than those in cold seasons (autumn and winter). Annual fractions of low molecular weight (LMW)-PAHs (2–3 rings, 12.1%) and high molecular weight (HMW)-PAHs (4–7 rings, 87.9%) indicated a strong contribution of thermal processes. Significant correlations between Σ19 PAHs and TSP (p < 0.01) at all the sampling sites were observed, implying that increased TSP levels were responsible for elevated levels of PAHs. There were strong seasonal variations in the profiles of PAHs, and they were clearly reflected in the results of the principal component analysis. Diagnostic ratios and backward air trajectories suggested seasonal variations in the contribution of local emissions and long-range transport. The diagnostic ratios suggested that mixed sources were dominant in cold seasons, while coal/biomass burning and non-traffic sources were prevailing in warm seasons. BeP/BaP ratios indicated that local emissions were major sources compared with long-range transport except for summer. Backward air trajectories in winter suggested the influence of long-range transport, but local emissions were more important in this study area.
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•Levels of particulate PAHs were monitored near a petrochemical industrial complex.•The concentrations of PAHs in warm seasons were lower than those in cold seasons.•Strong seasonal variations in the levels and profiles of PAHs were found.•The influence of local emissions and long-range transport was evaluated.•The industrial complex and domestic burning were identified as major sources of PAHs.
The number of antibiotic compounds in wastewaters has been growing globally due to the covid-19 problem. Using antibiotics to treat the patients would produce larger amounts of these compounds into ...the environment with negative impacts. Hence, finding out the method for the elimination of toxic organic pollutants as well as antibiotics in water is urgent (In this study, the treatment of antibiotic pollutants including cefalexin (CF) and tetracycline (TC) was investigated by applying the advanced oxidation process based on Ni-doped TiO2 (Ni–TiO2). The characterizations technologies such as XRD, XPS, UV–vis, PL, and PC indicated that Ni doping would improve the photocatalytic performance of TiO2.
In the photodegradation experiments, the Ni–TiO2 possessed high photocatalytic degradation efficiencies with 93.6% for CF and 82.5% for TC. Besides, the removal rates of antibiotics after five cycles are higher than 75%, implying excellent stability of Ni–TiO2 photocatalyst. The result from the treatment of wastewater samples revealed that the Ni–TiO2 photocatalytic had good performance for removal of CF and TC at a high level of 88.6 and 80.2%, respectively.
•Ni-doped TiO2 exhibits excellent photocatalytic performance for antibiotics degradation.•Degradation rate of antibiotic by Ni–TiO2 was 40% higher than that of undoped TiO2.•Reusability of Ni–TiO2 was higher than 75% after 5 cycles.•Ni–TiO2 could remove 88.6% of CF and 80.2% of TC 80.2% from wastewaters.
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•Highly efficient visible light driven photocatalyst S doped g-C3N4 was synthesized.•S doped g-C3N4 can reduce the recombination rate of electron-hole and narrowed band gap ...energy.•The S doped g-C3N4 had high recyclability and can reuse for 5 cycles.•TC was effectively removed from different wastewater by S doped g-C3N4.
Due to the coronavirus problem in 2020, lot of antibiotic compounds such as tetracycline (TC) have been used and discharge into water, leading to environment and human heal problem. Thus, preparing new catalysts for tetracycline removal have become a significant challenge in the areas of environmental engineering. Here we provide advanced photocatalyst based on sulfur (S) doped carbon nitride (CN) for treatment of TC. The characterization results confirmed that S doping reduced the recombination rates of electrons and holes, improved light absorption behavior. Under solar light the removal of TC just required only 30 mins and the degradation efficiency was 98.7%. S doped CN was able to degrade TC from different wastewaters with a maximum degradation efficiency of 93.8%. Furthermore, S-CN can be recycled multiple times, indicating it is suitable photocatalyst to solve the problem of antibiotic contamination in wastewaters.
Coconut shell activated carbon loaded with cobalt ferrite (CoFe2O4) composites (CAC/CoFe2O4) was synthesized via the single-step refluxing router method to manufacture adsorbents. The adsorbents were ...then applied to remove Rhodamine B (RhB) from aqueous environments via adsorption. The properties of coconut shell activated carbon (CAC) and CAC/CoFe2O4 were investigated through the usage of electron microscopic methods (SEM: Scanning Electron Microscopy, EDS: Energy Dispersive X-ray), powder X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). A series of batch experiments were implemented to evaluate the influences of various experimental parameters (initial pH, RhB concentration, contact time, and dosage of CAC/CoFe2O4) on the adsorption process. It was found that CoFe2O4 was successfully attached to activated carbon particles and had the suitable adsorption capacity for RhB at a molar ratio of 1 : 2:200 corresponding to the Co : Fe:CAC order. The removal efficiency and adsorption of RhB were optimal at a pH level of 4. The maximum adsorption capacity was 94.08 mg/g at an initial concentration of 350 mg/L and adsorbent dosage of 0.05 g/25 mL. Freundlich and Langmuir's models fitted well with the results obtained from the experimental data. The pseudo-second-order model also suited the most for RhB adsorption with the most remarkable correlation coefficient (R2 = 0.934). The adsorption process was controlled by a chemisorption mechanism through electrostatic attraction, hydrogen bonding interactions, and π-π interactions.
Halogenated polycyclic aromatic hydrocarbons (Halo-PAHs) are a new group of PAH derivatives and are reported to be more toxic than their parent PAHs. However, limited research has been undertaken on ...their physicochemical properties. In this study, sub-cooled liquid vapor pressures (PL) and octanol–air partition coefficients (KOA) of 24 chlorinated and 11 brominated PAHs (ClPAHs and BrPAHs) were determined using the gas chromatographic retention time (GC-RT) technique. The temperature dependences of PL and KOA for the Halo-PAHs were determined by the slopes and intercepts of the linear regressions. The GC-RT method also provided the enthalpies of vaporization (ΔHL) and internal energies of phase transfer (ΔUOA) for all interested compounds. The activity of Halo-PAHs in octanol (γoct) ranging from 18 to 87, indicated the non-ideal solution behavior. The number of the chlorine atoms in the PAH rings could influence the interaction of ClPAHs with the organic matter, whereas this interaction for BrPAHs could not be studied due to the limited number of target BrPAHs. The measured values of PL and KOA were applied to investigate the gas/particle partition behaviors of Halo-PAHs in Ulsan, South Korea. This study is so far the first one to report the linear regression coefficients, which can be used to estimate the PL and KOA values of Halo-PAHs at any temperature.
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•PL and KOA for Halo-PAHs were determined using the GC-RT method.•The values of PL and KOA for Halo-PAHs were correlated with molecular weights.•A range of γoct (18–87) for Halo-PAHs indicated the non-ideal solution behavior.•The number of chlorines influenced the interaction of ClPAHs with organic matter.•The values of PL and KOA were applied to investigate the G/P partitioning behaviors.
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