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N-doped sludge biochar prepared by pyrolysis of municipal sludge impregnated with NH4Cl solution and was used to investigate the effects of different factors on Cr(VI) adsorption-reduction. Furthermore, spectroscopic techniques were employed to investigate the structural feature of N-doped sludge biochar and the mechanism of Cr(VI) adsorption-reduction in depth. The results showed that compared with pristine sludge biochar (SBC), the Cr(VI) of removal efficiency and reduction efficiency on NSBC increased by 2.35 and 3.32 times, respectively. The removal of Cr(VI) by biochar was in accordance with the pseudo-second-order kinetic model and Langmuir model, and increasing the reaction temperature promoted the Cr(VI) removal by SBC and NSBC. The maximum adsorption amount of Cr(VI) by SBC and NSBC was 8.76 mg/g and 25.93 mg/g, respectively. The Cr(VI) reduction by NSBC was closely related to pH, and the reduction capacity of Cr(VI) under acidic condition was much higher than that under alkaline condition. Moreover, co-existing cations (Ca2+, Na+ and Mg2+) and coexisting anions (Cl-, NO3 and SO2- ) had no significant effect on Cr(VI) adsorption-reduction by NSBC, while humic acid inhibited the Cr(VI) removal by NSBC. The Cr(VI) removal from aqueous solution by NSBC involved Cr(VI) adsorption-reduction and Cr(III) release-adsorption. During the adsorption-reduction process, the persistent free radicals and N-containing groups on NSBC acted as reduction sites for Cr(VI). This work provided indepth mechanistic insight for N-doped biochar treating Cr(VI)-containing wastewater. [ABSTRACT FROM AUTHOR]4 ) had no significant effect on Cr(VI) adsorption-reduction by NSBC, while humic acid inhibited the Cr(VI) removal by NSBC. The Cr(VI) removal from aqueous solution by NSBC involved Cr(VI) adsorption-reduction and Cr(III) release-adsorption. During the adsorption-reduction process, the persistent free radicals and N-containing groups on NSBC acted as reduction sites for Cr(VI). This work provided indepth mechanistic insight for N-doped biochar treating Cr(VI)-containing wastewater. [ABSTRACT FROM AUTHOR]

Both biochars (BCs) and modified-biochars (MBCs) for toxic-metal/metalloid ions (TMIs) removal from water have caught much attention owing to their exceptional properties such as eco-friendly, low-carbon emission and cost-effective. However, reviews on the exploration of theoretical models of BCs and MBCs in various systems are unobtainable. To give a summary of theoretical models on BCs and MBCs for TMIs removal in various solution systems, this review will center on some typical kinetic and isotherm equations of BCs and MBCs for TMIs sorption in a single, mixed, mixed metal ions/organic substance solutions. Typically, two-parameter and threeparameter kinetic and isotherm equations of BCs and MBCs for TMIs sorption were stressed. The comparisons of these models in various solution systems were drawn. It was found that P-2nd-O kinetic model, Langmuir and Freundlich isotherm models are the dominating adsorption manners for TMIs in various MSSs. Especially, only the kinetic models of Cu(II), Pb(II), Cr(VI) and Cd(II) sorption, as well as the isotherms of Cu(II) and Cd(II) sorption on BCs and MBCs were reported in these MSSs. We hope such a summary will be favorable for the accurately selecting of optimal models to explain the sorption processes in different metal-solution systems. [ABSTRACT FROM AUTHOR]

Fe-containing sludge biochar produced by pyrolysis of Fe-containing residual municipal sludge was utilized for removing Cr(VI) from aqueous solutions. It was observed that increasing the solution pH decreased the adsorption performance of FSBC for Cr(VI), while raising the adsorption temperature enhanced Cr(VI) removal on FSBC. The coexisting ions of Na+, K+, SO42- and NO3- had minimal impact on removing Cr(VI) by FSBC, whereas the divalent cation of Ca2+ and Mg2+ exhibited a slight inhibitory influence on removing Cr(VI). Both the pseudo-first-order and Langmuir model were found to better describe the Cr(VI) removal process on FSBC from aqueous solutions. The mechanisms involved in removing Cr(VI) by FSBC may include complexation, electrostatic interaction and reduction processes. The Fe species present on FSBC were identified as both Fe2O3 and Fe3O4, with Fe3O4 disappearing after removing Cr(VI). The Fe species on FSBC provided Fe-O groups as site for removing Cr(VI), while Fe3O4 facilitated the Cr(VI) reduction by FSBC. This findings offered further viewpoints into removing Cr(VI) from aqueous solutions using Fe-containing sludge biochar. [ABSTRACT FROM AUTHOR]

This study examined the efficacy of ProsopisJuliflora with surface changes as a bioadsorbent for the removal of Allura Red dye. The effects of adsorptive dosage, pH, and contact period with starting dye attentiveness on adsorption were examined in the batch adsorption study. The study demonstrated that the Allura Red dye may be absorbed by surfaces that had been treated with KOH compound.The percentages of Allura Red dye eliminated were 67.18 %, 75.88 %, and 94.37 %, respectively. UV-visible adsorption spectroscopy is used to quantify the extent of dye decolorization. The modified surface characteristics of the adsorbent produced by ProsopisJuliflora were reported using XRD, FTIR, and SEM. The Adams-Bohart mathematical models are employed in the computation and assessment of adsorption efficiency. The adsorption-derived R² values for the equilibrium isotherm data model were 94.63, 86.67, and 96.35. Diffusion and intraparticle regeneration were investigated to bolster the adsorption investigation. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the design parameters for a filter intended to remove fluoride from groundwater. Water fluoridation notably influences groundwater, particularly in arid and semi-arid areas that exacerbate the challenge of availability of safe drinking water from Groundwater resources in numerous developing nations. Experiments were conducted to determine the fluoride concentrations in groundwater sources in the arid region of Maharashtra, India. Samples were collected from seven villages in three districts of Maharashtra. This study utilized chemically functionalized sugarcane bagasse biochar adsorbent (SCBB), which is low-cost and easily accessible, to remove fluoride from groundwater in a column setup. The recommended design parameters for the packed-bed column flow rate (Q) are 100 ml min-1 and bed height (d) is 30 cm. [ABSTRACT FROM AUTHOR]

The removal of anthracene from vehicle-wash wastewater (VWW) was investigated using adsorption employing biochar (EWB) generated from eucalyptus wood waste. The EWB was characterized using analytical techniques such as surface area analysis (SAA), scanning electron microscopy (SEM), and fourier transform infrared (FT-IR). The study determined that the most effective conditions to achieve maximum anthracene adsorption (98.40%) were as follows: an initial concentration of 40 ppm, a contact time of 60 min, a pH level of 5, a temperature of 50 °C, and an adsorbent dose of 0.4 g. Isotherms and kinetic models were utilized to evaluate the adsorptive capacity of anthracene. The kinetic analysis results indicate that the anthracene adsorption process onto the EWB is controlled by a pseudo 2nd order kinetic model. The experiment's findings showed that the Langmuir isotherm model provided the most accurate fit to the data. Also, error function analysis was performed. The exothermic and spontaneous nature of the adsorption process is evident based on the values of thermodynamic parameters, including enthalpy (ΔH°), Gibbs free energy (ΔG°), and entropy (ΔS°). The outcomes were also contrasted with the capabilities of a few commercial adsorbents in real-world applications. According to this investigation, the novel EWB exhibits a significant potential, which exceeds 95%, for the extraction and recovery of anthracene from industrial wastewater. [ABSTRACT FROM AUTHOR]

In this work, modified sludge biochar was prepared using molten salt-assisted pyrolysis method to remove Cd(II) from aqueous solution. The biochar was characterized using XRD, FTIR, Raman, XPS and pore structure analysis techniques, and the effects of initial pH, adsorption temperature, adsorption time and initial Cd(II) concentration on the Cd(II) removal were investigated. Compared with the virgin sludge biochar (VSBC), the modified sludge biochar (MSBC) by molten salt-assisted pyrolysis method was rougher surface, more developed pore structure and higher graphitization. The initial pH had a greater effect on the Cd(II) removal, and the high adsorption temperature promoted the Cd(II) removal. The Cd(II) removal behavior was in accordance with the pseudosecond- order kinetic model and Langmuir model, which indicated that the adsorption reaction was a single and uniform chemisorption. Thermodynamics indicated that the Cd(II) removal by VSBC and MSBC was spontaneous and heat-absorbing reaction. Additionally, the maximum adsorption capacities of Cd(II) by VSBC and MSBC were 39.02 and 101.26 mg/g at pH 5.0 and 25 °C, respectively. The mechanisms of Cd(II) removal included complexation of O-containing groups, ion exchange, precipitation, and electrostatic interaction. After three adsorption-desorption experiments, the Cd(II) removal efficiency by VSBC was maintained at 33.26%, while the Cd(II) removal efficiency on MSBC was maintained at 90.18%. This finding suggested that the modified sludge biochar using molten salt-assisted pyrolysis could be effective in remediating Cd(II)-contaminated water body. [ABSTRACT FROM AUTHOR]

In this work, sludge-based biochar was prepared from municipal sludge as raw material and coupled with zerovalent iron to obtain sludge-based biochar loaded with zero-valent iron (ZVI@SBC) for treating Cr(VI)-containing wastewater. Batch adsorption experiments were carried out to investigate the effects of adsorbent dosage, solution pH, adsorption time, adsorption temperature and pollutant concentration on the Cr(VI) removal by ZVI@SBC, and the potential mechanism of Cr(VI) removal by ZVI@SBC was investigated by characterization techniques. The optimum values of Cr(VI) removal efficiency and adsorption capacity by ZVI@SBC were achieved at the dosage of 25 mg. The Cr(VI) removal performance by ZVI@SBC existed strongly pH-dependent. Moreover, increasing the adsorption temperature promoted the Cr(VI) removal by ZVI@SBC. Notably, the Cr(VI) removal by ZVI@SBC was consistent with the pseudo second order kinetic model and the Langmuir model. The adsorption experiments showed that the maximum Cr(VI) adsorption capacity by ZVI@SBC was 150.83 mg/g at initial Cr(VI) concentration of 50-150 mg/L and adsorption temperature of 298 K. The Cr(VI) removal process by ZVI@SBC was homogeneous and chemical adsorption. The removal mechanism of Cr(VI) by ZVI@SBC was a complex process involving adsorption-reduction of Cr(VI) and release-adsorption of Cr(III). This work demonstrated that the sludge-based biochar loaded with zero-valent iron hold a better removal ability for Cr(VI) wastewater and provided a reference for the removal of Cr(VI) wastewater. [ABSTRACT FROM AUTHOR]

The use of three-dimensional (3D) electrochemical oxidation has become a popular method for treating water pollutants. In this study, the degradation of real wastewater discharged by the chemical industry was conducted using Pb loaded biochar (Pb/BC) as a particle electrode. The properties of Pb/BC were characterized by scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and Brunauer-Emmett-Teller. The impact of various factors, including Pb loading, pH, dosage of Pb/BC, and working voltage, on chemical oxygen demand (COD) elimination were examined, and the best results were obtained on pH 7 and working voltage of 14 V, with 25 g/L Pb/BC (8% Pb loaded on BC) added in 3D reaction system. The degradation process was well fitted with the first-order kinetic. COD removal efficiency was 67.60% after 90 min reaction with only 6.21 kW⋅h/kgCOD of energy consumption. The presence of tert-butanol had a significant impact on decreasing the efficiency of COD removal, suggesting that the hydroxyl radicals produced during the reaction were the primary means of degrading COD, rather than direct electro-oxidation. Toxic results indicated that the treated wastewater was less toxic than the original water. The use of Pb/BC may have practical applications in the treatment of actual chemical wastewater. [ABSTRACT FROM AUTHOR]

Low-cost biochar with a large surface area and enriched oxygen functional groups was prepared by pyrolysis of orange peel and post-NaOH modification. The modified orange peel-based bio-char (MOPBC) was examined for its performance in removing quinoline from aqueous solution by adsorption. As high as 197.53 mg/g of adsorption capacity of MOPBC for quinoline was achieved. The quinoline adsorption on MOPBC conforms to the pseudo-second-order kinetic model, well-fitted with the Freundlich isotherm model. Moreover, density functional theory calculation results show that quinoline is more readily adsorbed on oxygen-containing functional groups on the surface of MOPBC, especially hydroxyl groups. The plausible chemisorption mechanisms involve hydrogen bonding, acid-base interaction, π-π, and n-π interactions. This study proves that modified biochar is a prospective adsorbent concerning the disposal of quinoline in wastewater. [ABSTRACT FROM AUTHOR]

The simultaneous removal of heavy metals (Fe2+, Zn2+, Ni+2, Cr2+, and Cu2+) using filters built with cheap and easily accessible materials was studied in raw real wastewater generated from an electroplating industry localized in Medellín-Colombia. Various synthesized materials from banana peel waste were used as adsorbents, including powdered dry biomass and functionalized (chemically treated with activating agents) and unfunctionalized biochars, all obtained via hydrothermal and pyrolytic synthesis. For comparison, a commercial activated carbon (CAC) was employed. Significant variations in both structural and surface characteristics were observed among the materials depending on the activating agents utilized. As it was raw wastewater, the coexistence of multiple metals posed challenges in the objective comparison of adsorbents. Thus, the normalization of the maximum adsorption capacity about various parameters (for example, the amount of adsorbent, the specific surface area, the type and abundance of superficial functional groups, or the diameter and volume of the pore) confirmed the complexity of this type of process. In general terms, CAC and unfunctionalized biochar exhibited the highest adsorption capacities (for most metals). This suggests that, when employing banana waste adsorbents for the simultaneous removal of heavy metals in electroplating industry wastewater, the functionalization processes (which involve energy consumption, reagent usage, and waste generation) may not be necessary. [ABSTRACT FROM AUTHOR]

Biochar is an abundant, yet highly heterogenous, green alternative to the commercial activated carbons. As received, biochar possesses labile, soluble compounds that might obscure its utilisation in aqueous environments, for example, as porous electrodes for capacitive deionization. We investigated the effect of acid-base leaching on the physicochemical and electrochemical properties of straw biochar and commercial activated carbon. The findings suggested that the most commonly evaluated properties of the electrode materials (i.e., capacitance, resistance, functional groups, and porosity) do not unequivocally determine the electrode performance. The results point towards the importance of the more indefinite carbon properties, which differ between the pristine materials, arising from their inherent structural features, and could be related to their proton donating/accepting ability. [ABSTRACT FROM AUTHOR]

The heterogeneous micro-interface plays a crucial role in facilitating mass transfer and catalytic conversion. This study aimed to investigate the influence of the surfactant cetyltrimethyl ammonium bromide (CTAB) on micro-interface properties during sonocatalytic degradation of Orange II using bagasse biochar. Our findings indicate that increasing the concentration of CTAB or the dosage of bagasse biochar significantly enhances sonocatalytic degradation efficiency. However, an increase in solution pH was observed to have a detrimental effect on degradation efficiency, while higher ultrasonic power proved beneficial for Orange II degradation when CTAB was present. Moreover, the pseudo-first-order rate constant (Kapp) for the sonocatalytic process was 1.3 times that of the sum of combined Kapp values obtained with ultrasonication and biochar adsorption individually, indicating a substantial synergistic effect when bagasse biochar and ultrasonication are combined in the presence of CTAB. The influence of inorganic anions on sonocatalytic degradation of Orange II, in the presence of CTAB, was relatively weak. Quenching tests using iso-propanol and KBr indicated that free radical chain reactions predominantly occurred at the micro-interface, with limited involvement in bulk solutions during the sonocatalytic degradation process. Overall, our results indicate that OH radicals remained the dominant contributors to the overall reaction. [ABSTRACT FROM AUTHOR]

In this study, potassium hydroxide (KOH), aluminum chloride (AlCl3), and zinc chloride (ZnCl2) were co-pyrolyzed with pomelo peel biomass (according to different pyrolysis conditions, abbreviated in order as KOH-BC, AlCl3-BC, and ZnCl2-BC) to enhance the original biochar (BC) adsorption performance of an emerging contaminant tetrakis(hydroxymethyl)phosphonium chloride (THPC). The adsorption experiments indicated that the adsorption capacity for THPC of KOH-BC reached 438 mg·g-1, which showed much higher adsorption properties than those of BC (239.6 mg·g-1), AlCl3-BC (301.6 mg·g-1) and ZnCl2-BC (278.9 mg·g-1) due to its better developed pore structures. The adsorption process of THPC by BC, KOH-BC, AlCl3-BC, and ZnCl2-BC, a spontaneous endothermic process that had been analyzed, according with the second-order kinetic model and Langmuir isotherm model. And the adsorption mechanisms of THPC removal (i.e., pore filling, cation-p interaction, hydrogen bonding, and ion exchange) were summarized. Targeting Escherichia coli, the antibacterial activity of BC (THPC-BC) and KOH-BC (THPC-KOH-BC) of THPC after adsorption was explored. Antibacterial activity experiments have shown that THPC-BC and THPC-KOH-BC could effectively inhibit the growth of E. coli. Therefore, BC and modified BC can not only be used to remove THPC but also be recycled for secondary utilization, which provides a novel idea for the emission reduction and resource recycling of THPC with great practical value. [ABSTRACT FROM AUTHOR]

To enhance the Cd(II) adsorption capacity on sludge biochar (SBC), potassium permanganate modified sludge biochar (MSBC) was prepared. Additionally, the removal performance and adsorption behavior of Cd(II) on biochar were investigated by initial pH, coexisting ions, dosage, adsorption kinetics and adsorption isotherms. The Cd(II) adsorption behavior of SBC and MSBC was consistent with the pseudo-second-order kinetic model and the Langmuir model. The coexisting ion concentration of NaCl had almost no effect on the Cd(II) adsorption of SBC and MSBC. The maximum Cd(II) adsorption capacities of SBC and MSBC were 55.81 and 108.69 mg/g at the optimum conditions of 25°C, 1 g/L dosage and pH 5.0, respectively. After four replicate experiments, the removal efficiency of Cd(II) by SBC and MSBC was 64.05% and 90.34%, respectively. Complexation of Cd(II) with O-containing groups, Cd(II)-p interactions, co-precipitation and electrostatic interaction were the main mechanisms for the Cd(II) removal from aqueous solutions by SBC and MSBC. The KMnO4-modification effectively enhanced the number of O-containing groups in the biochar and enhanced the complexation of Cd(II) by MSBC, which was the main reason for the increased Cd(II) adsorption capacity of MSBC. The results showed that KMnO4-modification could effectively increase the Cd(II) adsorption by sludge biochar. [ABSTRACT FROM AUTHOR]

Carboxymethyl cellulose/biochar/polyacrylic acid composite (PAA/CMC/GBC) was prepared by hydrothermal synthesis of carboxymethyl cellulose and acrylic acid with ginger as raw material. The PAA/CMC/GBC were characterized by scanning electron microscopy, Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy (XPS). The adsorption capacity of PAA/CMC/GBC for Cu2+ and methylene blue was significant (maximum adsorption capacity at 25°C was 170 mg·g-1 for Cu2+ and 110 mg·g-1 for methylene blue), and showed good adsorption performance in a wide range of pH values (pH 2-12). The pseudo-second-order kinetics and Langmuir isotherm model are more consistent with the actual adsorption process. The results of XPS show that electrostatic attraction is the main adsorption mechanism of PAA/CMC/GBC for methylene blue (MB) adsorption, and metal complexation is the main adsorption mechanism of PAA/CMC/GBC for Cu adsorption. In addition, PAA/CMC/GBC adsorbents also showed good cyclic stability after repeated use. Therefore, PAA/CMC/GBC can be used as an efficient and environmentally friendly adsorbent to remove Cu2+ and MB dyes from aqueous solutions. [ABSTRACT FROM AUTHOR]

In this study, the effect of oyster shell powder as a substitute for calcium chemical reagents to modify straw biochar for enhancing removal of phosphate and ammonium from aqueous solution was investigated. The results showed that the biochar composite (OSB3:1) with the maximum capacity (151.37 mg·P/g and 0.8 mg·N/g) was synthesized at optimum mass ratio of oyster shell-to-straw (3:1) and pyrolysis temperature (800°C). The adsorption process followed the Langmuir isotherm and pseudo-second-order kinetic models, and it achieved excellent performance at pH 2.0-11.0. According to the thermodynamic analysis, the adsorption reaction was an endothermic and spontaneous process, and increasing the temperature increased the adsorption capacity. The removal mechanisms for phosphate included the formation of hydroxyapatite precipitation, ligand exchange, surface complexation and electrostatic attraction, while for ammonium only electrostatic attraction. The modified biochar can effectively remove phosphate (over 85%) from real domestic sewage within 3 h. Reuse of P-laden biochar as heavy metal adsorbent was proposed, as it exhibited a good removal efficiency for Cd, Zn and Cu, especially application for acidic wastewater. [ABSTRACT FROM AUTHOR]

The presence of complex functional groups and a well-developed pore structure make biochars highly effective in the removal of hazardous substances from water. In this work, peanut shell and orange peel biochars were produced by slow pyrolysis at different temperatures (300°C, 400°C, 500°C) for 6 h. The prepared biochars were used to treat phosphate in water to explore the effect of contact time and initial concentration of phosphate on adsorption performance. The kinetic models were fitted to study the adsorption mechanisms. The results showed that the highest yields of peanut shell (86.7%) and orange peel biochars (81.2%) were achieved at 400°C and 300°C, respectively. 5.0 g of peanut shell biochars removed about 5.94 mg/g phosphate in 26 h and the removal rate was 83.2%, while the same amount of orange peel biochars removed about 5.79 mg/g phosphate in 26 h and the removal rate was 81.1%. The adsorption processes of phosphate by peanut shell and orange peel biochars fitted with the secondary kinetic models, which were dominated by chemical adsorption. [ABSTRACT FROM AUTHOR]

This article describes the production of eucalyptus wood waste biochar (EWB) and its use in the adsorptive removal of naphthalene (Nap) from vehicle wash wastewater (VWW). EWB was produced by carbonizing the waste eucalyptus wood at a high temperature in a nitrogen atmosphere. The produced EWB was chemically activated by being subjected to 1 M HCl in order to increase its effectiveness. The EWB was described using pertinent instrumental techniques such as surface area analysis, Fourier-transform infrared spectroscopy, and scanning electron microscopy. Nap adsorption from aqueous solutions through EWB was examined using batch adsorption tests. As adsorption parameters, initial EWB concentration, contact time, pH, temperature, and adsorbent dose were all examined. Under ideal conditions, the adsorption efficiency was computed and the Nap contents were determined using a UV spectrometer. The optimal conditions for the highest adsorption of Nap from VWW on the EWB adsorbents were found to be an initial concentration of 30 ppm, contact time of 90 min, temperature of 60°C, adsorbent dose of 0.30 g, and 5 pH. Kinetic and isotherm models were applied to evaluate the adsorbent capacity to bind Nap. The kinetic study shows that the adsorption of Nap onto EWB is controlled by pseudo-second-order kinetics. The results of the experiment demonstrated that the Langmuir isotherm model offered the best fit for the data. The values of thermodynamic parameters such as entropy (Î"S°), Gibb's free energy (Î"G°) and enthalpy (Î"H°) show that the adsorption process is spontaneous and exothermic in nature. The trial results revealed that the highest adsorption at optimum condition for Nap from VWW was 98.65% (qe = 141.52 mg/g). The performances of certain commercial adsorbents utilized in practice were also compared with the results. This analysis showed that the new EWB has a significant potential (>95%) for removing and recovering Nap from industrial effluent. [ABSTRACT FROM AUTHOR]

Biochar can be a relatively inexpensive and effective material for removing polycyclic aromatic hydrocarbons (PAHs) from aquatic environment. An evaluation of the sorptive possibilities of biochar to remove PAHs from the aquatic environment was conducted. The content of benzo(a) pyrene and the sum of four PAHs, such as benzo(b)fluoranthene, benzo(k)fluoranthene, benzo( g,h,i)perylene and indeno(1,2,3-cd)pyrene were determined in water. The sorption process was carried out for biochar doses of 25, 50 and 100 mg/L. For each biochar dose, the contact time with PAHs was: 30, 60, 90 and 120 min. The best results were obtained for a biochar dose of 100 mg/L and a contact time of 120 min. For benzo(a)pyrene, the concentration decreased up to 78%, while for the four recommended PAHs, the greatest changes were shown for benzo(g,h,i)perylene and indeno(1,2,3-cd)pyrene, whose concentrations decreased by 81%. For the remaining PAHs, greater sorption was observed for dibenzo(a,h)anthracene, the concentration of this compound decreased by 81%. [ABSTRACT FROM AUTHOR]

Using agricultural and forestry waste biomasses as raw materials for the removal of organic dyes from wastewater is a cost-effective approach for environmental purification. In this paper, corn straws and poplar leaves were carbonized at different temperatures for 3 h to produce biochar-based adsorbents. Afterwards, with the addition of the prepared adsorbents to methylene blue (MB) wastewater, the effects of contact time, initial concentration of MB and adsorbent dosage on the adsorption performance were investigated. Meanwhile, both adsorption kinetic models and adsorption isotherm models were also studied to explore adsorption mechanisms of the obtained adsorbents. The physico-chemical properties of biochar-based adsorbents were subsequently characterized by scanning electron microscopy and Brunauer--Emmett--Teller. The results demonstrated that two biochar- based adsorbents produced from corn straws and poplar leaves at 300°C after 3 h carbonization achieved the highest yields of 90.5% and 90.7%, respectively. The removal rate of MB increased with contact time and the adsorption capacity for MB enhanced with initial concentration of MB by biochar-based adsorbents prepared by corn straws and poplar leaves. The highest removal rate of MB was 99.2% for corn straws biochar-based adsorbent at a dosage of 1.0 g and 95.1% for poplar leaves biochar-based adsorbent at a dosage of 1.5 g. Furthermore, the adsorption process of MB by corn straw and poplar leaf biochar-based adsorbents conformed to the quasi-second-order adsorption kinetic model and Langmuir model, which was dominated by chemical adsorption. [ABSTRACT FROM AUTHOR]

The present study evolved around the synthesis of trimetallic composite, manganese-zinc-cobalt hydrous oxides nanoparticles anchored biochar (MZCB) nanocomposite (NC) for decontamination of water and wastewater polluted with Cu(II) ions. The MZCB NC (27 nm) was characterized using Fourier-transform infrared spectroscopy, scanning electron microscopy-energy-dispersive X-ray spectroscopy and powder X-ray diffraction. Batch adsorption studies were performed and the influence of different adsorption parameters (contact time, reaction temperature, solution pH, adsorbent dose and initial adsorbate concentration) were examined. MZCB was found effective in removing (~98%) of Cu(II) in 50 min at pH 5.0 while employing initial dose of 0.1 g and 300 mg·Cu(II)·L-1. The adsorption experimental data was fitted to different adsorption isotherms and kinetic models which exhibited best-fit models to be the general order kinetic model and Redlich--Peterson adsorption model, respectively. The maximum uptake capacity of MZCB with respect to Cu(II) ions was found to be 312.58 mg·g-1. [ABSTRACT FROM AUTHOR]

The current study reports batch studies using eucalyptus wood waste derived biochar (EWB) to adsorb Cr(VI) and Cu(II) from aqueous solutions. Scanning electron microscopy, specific surface analysis, and Fourier-transform infrared spectroscopy were used to study the morphology and structure of the EWB. A thorough analysis of the variables affecting adsorption performance was conducted. The Freundlich isotherm, Langmuir isotherm, pseudo-second-order, and pseudo- first-order models were used to study the adsorption process. The optimal conditions for the highest adsorption of Cr(VI) and Cu(II) as of aqueous solution on the EWB adsorbents were found to be an initial concentration of 30 ppm, contact time of 60 min, temperature of 60°C, adsorbent dose of 0.20 g, and 3, 6 pH. The adsorption system, according to kinetic studies, follows a pseudo- second-order equation. It was shown that the experimental results for the adsorption of Cr(VI) and Cu(II) on EWB were best suited by the Langmuir equation. The trial results revealed that the highest adsorption at optimum condition for Cr(VI) and Cu(II) from aqueous medium was 96.23% and 98.46%, respectively. The produced EWB have a high adsorption capacity (>95%) and a porous structure that make them very attractive as an alternative to Cr(VI) and Cu(II) adsorbents. [ABSTRACT FROM AUTHOR]

Fluoride pollution in groundwater is mainly from natural factors, which will harm those who use groundwater as drinking water. Herein, an iron-lanthanum watermelon rind biochar composite was prepared by a coprecipitation method and used to remove fluoride from the aqueous solution by a static adsorption method. The effects of adsorbent composition, aging time, calcination temperature, pH, adsorption time, adsorbent dosage, adsorption temperature, initial concentration of fluoride, and coexisting anions on the removal of fluoride were evaluated. When the amount of adsorbent was 0.05 g/50 mL, the removal efficiency of the fluoride with an initial concentration of 10 mg/L reached 98.29%. The best conditions for the static adsorption process of 10 mg/L fluoride were: pH was in the range 2-9, the amount of adsorbent was 0.05 g/50 mL, and the reaction time was 5 h. Scanning electron microscopy-energy-dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Brunauer--Emmett--Teller of the adsorbent were tested. Experimental results showed that electrostatic attraction, metal complexation, and ion exchange were the main adsorption mechanisms. The calculated value of k2 varies from 0.2943 to 0.0071 g/mg·min with the decrease of the fluoride concentration. The kinetics and isotherm showed that chemical adsorption was the main control step in the fluoride adsorption of Fe-La-WBC-300. The value of the Freundlich constant (n) in the range 0-1 showed that Fe-La-WBC-300 had the best performance for fluoride removal. The fluoride adsorption process consisted of single-layer adsorption and multilayer adsorption. Thermodynamic studies showed that the adsorption of fluoride was a process of spontaneous endothermic reaction. Fe-La-WBC-300 showed a good application prospect to remove fluoride in groundwater. [ABSTRACT FROM AUTHOR]

This study attempted to analyze the effect of biochar fertilization with the biomass of Virginia fanpetals (Sida hermaphrodita) on selected physical and chemical properties of sandy soil. The biomass yield of three energy crop species grown on such fertilized soil was evaluated. The content of heavy metals accumulated in the biomass of selected energy crops and the soil after crop cultivation was also determined. The examinations were carried out under conditions of the lysimeter experiment (natural conditions). Sandy soil was used for fertilization, with biochar doses of 0.5%, 1%, 1.5%, and 2% (by weight). The control material was non-fertilized soil. The study was carried out for 3 y. After each growing season, selected soil properties, the volume of biomass obtained, and the bioaccumulation of heavy metals were analyzed. Fertilization of the sandy soils with biochar caused a significant increase in the yield of all three energy crops studied, including Sida hermaphrodita. Of all the species cultivated, this plant responded best to biochar amendment. An optimum dose of this fertilizer was 1.5%, which, in the first year of cultivation, caused an increase in yield by 21.1% compared to control plants. The study showed that the use of biochar as a fertilizer did not cause an increase in contamination of the sandy soils with heavy metals. The application of biochar to sandy soil with all doses resulted in an improvement of selected sorption properties including a statistically significant increase in pH (active acidity), a decrease in hydrolytic acidity (potential acidity), an increase in the content of phosphorus, nitrogen, total carbon, and organic matter. [ABSTRACT FROM AUTHOR]

Commercial activated carbons are mainly used in the adsorption process to remove pollutants from water and wastewater, however, due to their high costs, substitutes are currently being sought. Carbon materials obtained from activated biomass often show a high specific surface area (similar to that for activated carbons) due to a well-developed pore structure. In this study, activated biochar obtained from sunflower husks was tested for the adsorption of povidone-iodine (PVP-I) and methylene blue (MB). The biochar was prepared in the pyrolysis process (500°C) and chemically activated with K2CO3 at a temperature of 800°C. The activation affected greatly the structural properties of the biochar -- the specific surface area increased from 32.5 to 740.5 m2/g, and the micropore and mesopore volume increased over 20 and 15 times, respectively. Also the iodine value changed from 89 to 495 mg/g. The physicochemical and granulometric properties as well as pH value of point of zero charge of the adsorbent surface were determined. The central composite design method was used to determine the optimal adsorption conditions (solution pH and adsorbent mass) in the initial concentration range 10-60 mg/dm³ for PVP-I and 30-250 mg/dm³ for MB. The maximum sorption capacity reaches 120 mg/g for MB and 5.6 mg/g for PVP-I. Sorption kinetics was investigated with use of several models. The times of half-saturation for these adsorbates are around 1 and 15 min, respectively. The detected Gibbs free energy change indicates the adsorption is spontaneous and thermodynamically favored. The adsorptive properties of the biochar obtained from waste sunflower husk are especially good for MB adsorption and acceptable with respect to PVP-I adsorption. [ABSTRACT FROM AUTHOR]

Organic pollutants in wastewater became a major challenge in the field of environmental remediation. In this work, biochar-loaded nano zero-valent iron (BC@nZVI) was successfully prepared and used to activate persulfate (PS) for Rhodamine B (RhB) removal from water. The structure and morphology of the nanocomposites were characterized by scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy, X-ray diffraction, Brunauer-Emmett-Teller testing, and Raman spectroscopy. The effects of pyrolysis temperature and iron loading on RhB removal were investigated, and the optimum conditions of RhB removal were determined by reaction parameters: BC@nZVI dosage, PS concentration, pH values, reaction temperature, and inorganic anions in the BC@nZVI/PS system. Acidic and high-temperature conditions were more favorable for RhB removal. Additionally, free radical burst tests and electron paramagnetic resonance assays showed that SO4 •-and •OH were generated and worked in the removal process, while SO4 •- is the main active species. BC@nZVI is an excellent catalyst for the treatment of RhB and provides an eco-friendly strategy for the treatment of organic pollutants in wastewater, with a broad application prospects. [ABSTRACT FROM AUTHOR]

Conventional wastewater treatment is inefficient in removing Rhodamine B (RhB) from dying wastewater. Wastewater treatment is a promising advanced oxidation process (AOP) based on biochar and iron-activated persulfate. Therefore, the current study explored the potential of iron-loaded biochar-activated persulfate to remove RhB. Based on morphology observation, iron-loaded biochar could be successfully prepared using slow pyrolysis inside an N2 environment at 800°C. Structure analysis revealed that the surface area of iron-loaded biochar was 1.5 times the size of unmodified biochar. Under the optimum reaction condition, the maximum removal rate of RhB was 99.96%, determined by single-factor experiments. The RhB removal rate was improved with increased activator dosage, PS dosage, and temperature but decreased with increased pH and initial dye concentration. The RhB adsorption rate was governed by pseudo-first-order reaction kinetics, and the Langmuir-Hinshelwood kinetic model (R2 = 0.99853) helped explain the adsorption behavior. Recycling experiments of Fe-BC indicated a twice-cycle capacity which could be improved. Free radical quenching experiments showed that sulfate-free (SO4 •-) and hydroxyl (•OH) radicals worked together in the RhB removal process, dominated by •OH. [ABSTRACT FROM AUTHOR]

This study aimed to explore the Cr(VI) removal performance and mechanism of distillers' grainsbased biochar. Biochar was prepared at 600°C and modified with an alkaline solution (1 M KOH). In this study, factors affecting adsorption efficiencies such as biochar dosage (1~3 g/L), pHinitial (2.0~7.0), Cr(VI) initial concentration (10~300 mg/L), and adsorption time (0-24 h) were explored. The results showed that compared with the original biochar, the adsorption efficiency of Cr(VI) on the modified biochar after treatment with KOH solution was increased by 3 times. Scanning electron microscopy and Fourier-transform infrared spectroscopy analysis indicated that the morphology and function of biochar changed significantly after modification. When the dosage of modified biochar reaches 3.0 g/L, the removal rate of Cr(VI) of 50 mg/L can reach 99.99%. The initial pH of the solution is an essential adsorption parameter to determine the adsorption capacity of biochar. The removal efficiency of Cr(1) in the solution with lower pH is higher. The adsorption behavior of the modified biochar was more consistent with Freundlich isothermal adsorption model and the quasi-second-order kinetic equation. The theoretical equilibrium adsorption capacity Qe of KBC-2, KBC-1, and BC were 29.54, 19.76, and 9.37 mg/g, respectively. Thermodynamic studies indicate that the adsorption of Cr(1) by KABC-1, KABC-2, and BC is an automatic and endothermic process. In addition, the adsorption mechanism of Cr(1) by modified distillers' grains biochar can be explained as the synergistic action of chemical and physical adsorption. [ABSTRACT FROM AUTHOR]

In this study, the adsorption of Amaranth (AR) and Fast Green FCF (FG) by walnut shell biochar (WB) and Fe-impregnated WB with iron mine tailing wastes (MWB) was examined to identify the differences in their adsorption mechanisms. The physico-chemical properties of WB and MWB were analyzed using ultra-high-resolution scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy (XPS), and X-ray diffractometer. The adsorption of AR and FG using WB and MWB fit the pseudo-second-order kinetic (R² : WB = 0.997–0.999, MWB = 0.994–0.998) and Freundlich isotherms (R² : WB = 0.738–0.927, MWB = 0.983–0.993) better than the pseudo-first-order kinetic (R² : WB = 0.657– 0.969, MWB = 0.982–0.987) and Langmuir isotherms (R² : WB = 0.711–0.806, MWB = 0.965–0.988). This result suggests that the adsorption of AR and FG onto WB and MWB is governed by chemisorption and multilayer adsorption. Based on the differences in the XPS spectra of WB and MWB before and after the adsorption of AR and FG, the adsorption mechanism of AR and FG onto WB and MWB suggests that the hydrophobic interaction and electrostatic force governs the adsorption of AR and FG. Even following three adsorption–desorption cycles with MeOH, MWB continued to exhibit exceptional reusability (AR = 61.03%, FG = 75.42%). This finding implies that the impregnation of iron materials on the WB surface benefits the adsorption of synthetic dyes in aqueous solutions [ABSTRACT FROM AUTHOR]

In this work, magnesium-modified rice straw biochar (MgBC) was prepared by chemical impregnation, and the effects of proportion, initial pH, contact time, temperature and initial concentration on the removal of Cd(II) and Pb(II) by MgBC were investigated. Additionally, scanning electron microscopy, Brunauer–Emmett–Teller, Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) were used for the characterisation of MgBC. The results shown that MgBC surface contained massive Mg-particles and possessed more abundant O-containing groups. Batch adsorption experiments shown that the optimum adsorption efficiency of Cd(II) and Pb(II) by MgBC was achieved at ratio of 1:2 and initial pH of 6.0. The pseudo-second-order kinetic model and the Langmuir isothermal model could better describe the removal of Cd(II) and Pb(II) by MgBC. The maximum adsorption capacity of Cd(II) and Pb(II) by MgBC was 92.68 and 128.06 mg/g at pH 6.0, 35°C and initial concentrations of 10~100 mg/L, respectively. FTIR and XRD analysis shown that the removal mechanism of Cd(II) and Pb(II) by MgBC involved complexation, ions exchange, co-precipitation and electrostatic interaction. After 4 adsorption–desorption experiment, the removal efficiency of Cd(II) and Pb(II) by MgBC remained above 80%. This results indicated that MgBC had great potential for the treatment of wastewater containing Cd(II) and Pb(II). [ABSTRACT FROM AUTHOR]

In this study, durian rind-derived (DR) biochar was used for MnII and FeIII removal from aqueous solution. The removal test was conducted on a batch scale with known concentrations of MnII and FeIII solutions (5-50 mg/L) at pH 2, 4, 7 and 9. The results showed that the precipitation mechanism dominated at basic pH values while adsorption was the main mechanism under acidic conditions. Langmuir and Freundlich adsorption isotherms were used in this study to identify the adsorption behavior. The maximum adsorption capacities of MnII and FeIII by the biochar were 24.16 and 16.92 mg/g, respectively. The maximum adsorption ability of MnII onto the biochar was higher than that of FeIII, which was attributed to the ionic radius and electronegativity of metal ions. Two ground-water samples representing MnII-rich (named HL with 11 mg/L Mn) and FeIII-rich (named RT with 37 mg/L Fe) samples collected from locations close to gold mines were used for the removal tests. Almost 100% of both metals were removed, even under acidic conditions (pH 4). Due to its high efficiency and low cost, DR biochar shows great promise as an attractive adsorbent for metal-ions removal. [ABSTRACT FROM AUTHOR]

The treatment of effluents containing emerging contaminants, such as chlorophenols (CPs), by biochar adsorption has been a hotspot topic. However, the interaction between CPs in the adsorption process on biochar is still unknown at present. In this paper, two kinds of biochar were prepared from corn straw under pyrolysis of 300°C and 600°C, labeled as BC300 and BC600, respectively, and were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, and Fouriertransform infrared spectroscopy. The adsorption process and mechanism of biochar on CPs, including phenol (PHE), 4-chlorophenol (4-CP), and 2,4-dichlorophenol (2,4-DCP), were investigated using the batch equilibrium experimental method in a single component system (SCS) and multi-component system (MCS), respectively. The adsorption regularity of CPs on biochars in the MCS resembles that in the SCS. In the MCS, the pseudo-second-order kinetic model is fitted better for the adsorption process of CPs on biochar (R² ≥ 0.938). The maximum adsorption capacity (qm) of PHE, 4-CP and 2,4-DCP is 28.16, 32.54 and 36.04 mg/g, respectively. The isotherm adsorption process is fitted more consistent with Langmuir–Freundlich model (R² ≥ 0.913). The qm of PHE, 4-CP and 2,4-DCP in the MCS is 43.02, 60.85 and 96.48 mg/g, but the qm of PHE, 4-CP and 2,4-DCP in the SCS is 63.91, 121.03 and 145.09 mg/g, respectively. The pH value of solution is a key factor influencing the adsorption of CPs on the biochar. At pH < 9, the adsorption capacity (qe ) of CPs on biochar almost remains constant as increase of pH values. By way of the contrast, at pH > 9, the qe of CPs decreases rapidly with increasing pH values. However, there is an interaction between CPs in the adsorption process on biochar in the MCS compared with that in the SCS, that is, one or two of three co-existing pollutants can inhibit the adsorption of each of CPs on biochar. Furthermore, the adsorption capacity of CPs on biochar increases with the number of chlorine atoms in CPs, that is, the more chlorine atoms in CPs, the easier it is to be adsorbed on biochar. [ABSTRACT FROM AUTHOR]

Phosphate-modified biochar is a good material for the heavy metals removal from wastewater. However, different phosphate modified straw biochar have dissimilar adsorption performance for heavy metals. In this work, Na3PO4 -modified straw biochar (PBC) and Na2HPO4 -modified straw biochar (SPBC) were used to remove Cd(II) from aqueous solution. Moreover, the effects of dosage, solution pH, coexisting ions, adsorption time, temperature and initial concentration on the Cd(II) removal by the sorbent were investigated. The result shown that SPBC possessed richer pore structure and O-containing functional groups. The adsorption experiments indicated that the optimum adsorption performance could be obtained at pH = 6.0 and dosage 25 mg. K+, Na+, Ca2+ and Mg2+ had little effect on the removal of Cd(II) by biochar, while Cu2+ and Pb2+ had strong inhibitory effect. Notably, SPBC reached the time of adsorption equilibrium much faster than biochar (BC) and PBC. The pseudo-second-order kinetic model and Langmuir model could describe the adsorption process of Cd(II) well. The theoretical maximum adsorption capacities of BC, PBC and SPBC for Cd(II) were 54.55, 114.79 and 154.13 mg/g at 25°C, respectively. The removal mechanisms included complexation, ion exchange, Cd(II)-π interaction, electrostatic interaction and co-precipitation. This work suggested that Na2HPO4 -modified straw biochar held greater potential to remove Cd(II) from wastewater than Na3PO4 -modification. [ABSTRACT FROM AUTHOR]

In this work, a local Algerian agricultural waste biomass, Ziziphus jujuba, was valorized into a new low-cost biochar (JB). The biochar was produced by a simple pyrolysis at 700°C for 1 h under an inert atmosphere and was used as a low-cost adsorbent to remove Indigo carmine dye (IC) from aqueous solution. The JB biochar was characterized by Fourier-transform infrared spectroscopy, scanning electron microscopy-energy-dispersive X-ray spectroscopy, X-ray diffraction, Raman, pHpzc, and Brunauer–Emmett–Teller physico-chemical techniques. Adsorption studies were conducted using a batch process to study the effects of contact time, adsorbent amount, initial IC dye concentration, initial pH, ionic strength, and temperature. The Langmuir, Freundlich, and Temkin isotherm models were used to analyze equilibrium adsorption data, while the pseudo-firstorder, pseudo-second-order, Elovich, and intraparticle diffusion models were used to analyze kinetic data. The equilibrium data was well fitted to the Freundlich isotherm with an R² value of 0.974. The theoretical maximum adsorption capacity was found to be 166.46 mg/g at 20°C according to the Langmuir model. The adsorption kinetic was found to follow the pseudo-first-order kinetic model. Thermodynamic study showed that the adsorption of IC onto JB biochar was feasible, spontaneous and endothermic. [ABSTRACT FROM AUTHOR]

In this work, we investigated the potential of pristine biochar (obtained from poultry manure by pyrolysis at 725°C in a laboratory pyrolysis reactor under N2 environment) as an efficient adsorbent for removing tetracycline (TC) and rhodamine 6G (R6G) from aqueous solutions. Microscopic and spectroscopic analyses demonstrated a developed surface of the investigated biochar free from toxic organic compounds that could form within the annealing. The removal of TC and R6G was analyzed with UV-vis spectrometry in the function of the pH, ionic strength, and adsorbent dosage. The maximal adsorption capacity for TC and R6G is 65 and 63 mg g–1, respectively, indicating that pristine biochar from poultry manure has an excellent adsorption ability for both compounds demonstrating its high potential for removing various compounds of this type from water media. The enhanced adsorption on the investigated biochar is mainly controlled by the strong π–π and n–π interactions between the surface of the biochar and the two contaminants. The investigated poultry manure derived biochar can be a promising “green”, sustainable and carbon-rich material for low-cost and facile environmental applications, including the removal of contaminants from municipal wastewater. [ABSTRACT FROM AUTHOR]

Industrial wastewater of cadmium ions in the environment needs to be solved urgently. Nanohydroxyapatite and low-cost rice husk-egg shells biochar were successfully hybridized to form nano-hydroxyapatite/biochar hybrid materials (HBC) for the adsorption of Cd2+ in aqueous solution. Scanning electron microscopy, BET, X-ray diffraction and Fourier-transform infrared spectroscopy were used to characterize HBC. The results showed that compared with the biochar (BC), the adsorption efficiency and adsorption capacity of HBC were greatly improved. Specifically, the adsorption efficiency was increased by 50%, and the saturated adsorption capacity was increased from 23.835 to 35.2875 mg/g, which was increased by 48%. The adsorption mechanism of HBC on Cd2+ is complex. Chemical adsorption and multilayer adsorption provide the most important contribution, and various adsorption methods such as surface complexation, ion exchange, dissolution and precipitation also affect the adsorption of Cd2+. In general, HBC is an efficient and environmentally friendly adsorbent, which can be used for the removal of Cd2+ from aqueous solution and has high adsorption capacity and cost effectiveness. [ABSTRACT FROM AUTHOR]

The current study reports the adsorption of aluminum (Al3+) from aqueous solutions through batch experiments using eucalyptus wood waste-derived biochar (EWB). The EWB morphology and structure were observed by surface area analysis, scanning electron microscopy, as well as Fouriertransform infrared spectroscopy. A thorough analysis of the variables influencing adsorption performance was conducted. The adsorption process was examined using the Freundlich, Langmuir, pseudo-second-order models as well as pseudo-first-order. The EWB showed a high adsorption rate in low concentration Al3+ solutions. The adsorption of Al3+ was exothermic and spontaneous. The prepared EWB are very promising as an alternative adsorbent for Al3+ due to their porous structure and high adsorption capacity (>90%). [ABSTRACT FROM AUTHOR]

Recently, biochar with persistent free radicals has widely been applied to the removal of nutrient in bioretention cells. However, there is a lack of information on hydrogen peroxide (H2O2) levels in biochar-based bioretention cells with three environmental conditions and its potential risks. In this study, batch experiments were used to investigate H2O2 levels in biochar-based bioretention cells with different weight ratios of sand to biochar (S/B), hydraulic loading rate (HLR) and antecedent dry period (ADP). Potential risks of H2O2 on dominant community were also explored. Results showed that H2O2 levels in bioretention cells with 9:1, 8:2 and 7:3 of S/B were significantly high with the range from 0.024 to 0.044 mmol/L, and the production decreased with the increasing contents of biochar. Furthermore, H2O2 levels in three different heights of substrate layers and the bottom outlet enhanced with the rise of HLR, where the amplification of H2O2 in the middle layer was the largest, reaching 438.5% (ratio of H2O2 level at 2.0 m3/m2/d of HLR to the one at 0.4 m3/m2/d of HLR). In contrast, the long ADP was unfavorable to H2O2 levels in biochar-based bioretention cells. The production of H2O2 resulted in the change of dominant microflora (Bacteroidetes and Firmicutes), and the dosage of biochar could be the key. Altering these mentioned factors to achieve the regulation of microbial community structure in bioretention cells with biochar could be one of the promising approaches for the improvement of biological degradation function. [ABSTRACT FROM AUTHOR]

This article reports the application of United Arab Emirates (UAE) Arecaceae leaves biochars for adsorptive removal of Rhodamine B (RhB) from an aqueous solution at room temperature. Adsorption of RhB onto Arecaceae leaves biochar was proved by using Fourier-transform infrared spectroscopy. The morphology of Arecaceae leaves biochar was investigated by scanning electron microscopy. The influence of operational parameters on the percentage removal of RhB was explored in detail. Results showed that the percentage removal of RhB was increased with contact time and mass of UAE Arecaceae leaves biochar, whereas presented an inverse relation with initial concentration of RhB dye solution as well as temperature. Adsorption kinetics study showed that RhB adsorption onto UAE Arecaceae leaves biochar fitted to pseudo-second-order kinetics rendering the value of correlation coefficient (R² = 0.998) close to unity. Several adsorption isotherms were used to explore adsorption of RhB onto UAE Arecaceae leaves biochars. Results represented that RhB adsorption onto Arecaceae leaves biochars fitted well to Langmuir isotherm with correlation coefficient value close to unity (R² = 0.999). The values of Gibb’s free energy (ΔG°), enthalpy (ΔH°), and entropy (ΔS°) were measured to study adsorption thermodynamics for the dye onto Arecaceae leaves biochars. Attained results represented that RhB adsorption from an aqueous solution onto Arecaceae leaves biochars was an exothermic process (ΔH° = –16.30 kJ/mol). The positive value of Gibb’s free energy showed that RhB adsorption was a non-spontaneous process. [ABSTRACT FROM AUTHOR]

Residual antibiotics in the environment pose a serious threat to the environment. To solve the problems of inter-particle agglomeration, metal ion leaching and difficult recovery of transition metal oxides as catalysis in advanced oxidation processes for the treatment of antibiotic wastewater, pine needle biochar loaded with iron–nickel bimetals (Fe/Ni@PNBC) were successfully produced by the impregnation–co-precipitation method to activate peroxymonosulfate (PMS) for degradation of oxytetracycline (OTC). The Fe/Ni@PNBC catalyst has good surface properties, abundant functional groups and catalytic stability. Under the optimal conditions, the degradation efficiency of OTC with initial concentration of 10~60 mg/L is close to 90%. In addition, 1O2 and O2 •– played a major role in OTC degradation. The reaction mechanism for generation of active species and OTC degradation in the reaction system was proposed from two perspectives including redox of iron and nickel ions in different valence states and interconversion between the active substances. After 5 cycles, Fe/Ni@PNBC still maintained a high catalytic activity for OTC degradation. This study provides a new method to prepare an economical and environmentally friendly catalyst for activating PMS to treat antibiotic wastewater. [ABSTRACT FROM AUTHOR]

Water containing Cr(VI) causes health effects, which makes their treatment necessary. In this work, biochar from sunflower seeds waste was used to remove Cr(VI) from water. The biochar was modified by magnesium and optimized. The Mg-biochar was characterized by Fourier-transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy (SEM), atomic force microscopy, and ASAP methods. The SEM images of Mg-biochar showed magnesium oxide spherical particles with nanoflakes. The Mg-biochar specific surface area and pore volume were 67.85 m2/g and 0.061 m3/g, respectively. Cr(VI) adsorption decreased from 87.16% to 50.76% with an increase in pH from 2 to 10. The isotherm of the Cr(VI) adsorption by Mg-biochar followed the Langmuir model. Thermodynamic studies showed the endothermic nature of the adsorption. Kinetics of Cr(VI) adsorption by Mg-biochar was in agreement with the pseudo-second-order model and its rate constant was 2.1 g/mg·min which was large in comparison with other works showing advantage of fast removal kinetics of Mg-biochar. The Mg-biochar adsorbent had the removal of 74.5% under the operating conditions of Cr(VI) initial concentration of 10 mg/L, adsorbent dose of 15 g/L, pH of 5, and time of 15 min. [ABSTRACT FROM AUTHOR]

Fish feces and residues are a kind of common waste in aquaculture system to require timely handling while aquaculture wastewater generally contains antibiotics to require efficient treatment. This study prepared biochar by using fish feces and residues to investigate the removal of typical fluoroquinolone enrofloxacin by biochar. Biochar showed the sheet-dot mixed structure with multiple elements on surface. The content of carbon/nitrogen/hydrogen of biochar made of fish feces and residues reached 46.5%/3.1%/2.5%. The removal efficiency of enrofloxacin reached 94.7% with biochar dosage of 1 g/L. The adsorption capacity of biochar at pH of 2 or 10 was higher than that at the other pH values. Adsorption capacity of biochar increased by 10.6% from 15°C to 25°C to reach 9.47 mg/g at 25°C while that slightly increased from 25°C to 35°C. Pseudofirst-order model was the best model with R² = 0.9982 for describing adsorption kinetics of enrofloxacin by biochar. Langmuir model could better fit results of isotherm for enrofloxacin by biochar with Langmuir constant of 0.38–1.65 L/mg. Biochar used 3–4 times still kept good removal efficiency for enrofloxacin. The prepared biochar exhibited good application potential. The findings of this study provide new idea for treating aquaculture solid wastes and wastewater. [ABSTRACT FROM AUTHOR]

Biochar obtained from Moringa seeds husks was functionalized with protein extracted from Moringa kernels powder resulting in a composite biochar (BC-MOP). The functionalization of its surface was characterized by FTIR spectroscopy, which showed the appearance of peaks indicative of protein functions (amines and ketones), confirming the consolidation of the surface. This composite was tested in humic acid (HA) removal from an aqueous solution, and its adsorption capacity was evaluated by comparison with that of biochar (BC). Removal rates favored the composite 81.4 mg g0 for BC-MOP and 41 mg g–1 for BC when the temperature was 25°C which demonstrated the impact of functionalization. The operating parameters pH, contact time, and dose of adsorbent were optimized, and it was found that solution pH played a crucial role in the adsorption process. The adsorption isotherms of the HA fit the Langmuir model better than the Freundlich model, and the adsorption kinetics followed the pseudo-second-order model. The adsorption was chemisorption in nature. The degradation of HA into units of low molecular weight substances was proved by FTIR spectrum and UV absorption after adsorption of HA. This study contributed to the development of new composite biochars with high adsorbent capacity toward organic pollutants. [ABSTRACT FROM AUTHOR]

A novelty and economy of β-cyclodextrin (β-CD) functionalized sycamore leaf-based biochar (BC) was synthesized, namely β-BC, and was used to study the potential adsorption mechanism of Pb(II) in water. Through scanning electron microscopy, Brunauer--Emmett--Teller, Fourier-transform infrared spectroscopy and X-ray diffraction characterization analyses, it was confirmed that the β-CD was successfully loaded. A succession of kinetic adsorption, isothermal adsorption and influencing factor experiments were carried out. The results showed that when compared with BC, the time for β-BC to reach adsorption equilibrium was reduced by half, and the removal efficiency increased from 89.84% to 98.48%. Meanwhile, the optimal pH was 5.0 and the dosage of β-BC was 0.05 g. The pseudo-second model and Freundlich isotherm model fitted the adsorption process for β-BC well. The maximum adsorption of Pb(II) in a single system was 151.2 mg g-1, and the adsorption of binary systems was 92.03 mg g-1, it was proved that Cd(II) has exert a competitive effect on Pb(II). The results demonstrated that β-BC has efficient and fast removal of Pb(II), it was primarily attributed to electrostatic action, complexation, hydrogen bonding of a wealth of oxygenated groups on the surface, and host-object interaction in the β-CD cavity. This research confirmed the extraordinary potential of β-BC to treat heavy metals in wastewater. [ABSTRACT FROM AUTHOR]

Biochar- and zeolite-supported iron oxide catalyst (BC-Fe and Z-Fe, respectively), were prepared from industrial by-products using a solvent-free method. The effectiveness of the prepared catalysts was tested by conducting batch experiments to remove methyl orange (MO) dye from dyeladen water. The optimum process variables for a maximum removal efficiency were identified using the Box–Behnken design of experiments (DoE) technique. The variables chosen were contact time, adsorbent dosage, pH, and initial adsorbate dosage. BC-Fe has a removal efficiency of 95% at a high acidic pH with a lower adsorbent concentration (3–5 g/L), as compared to that of the Z-Fe adsorbent (4–5 g/L). The higher surface area and pore volume of BC-Fe (66.998 m2/g, 17 cc/g) than that of Z-Fe (50.039 m2/g, 13.07 cc/g) resulted in a better removal efficiency with a low adsorbent dosage. Statistical verification was performed to check the real-time robustness of the developed Box–Behnken DoE model. The methyl orange (MO) dye adsorption was best described by the Langmuir, Freundlich and Temkin adsorption isotherms. Kinetic studies revealed that the pseudo-second-order kinetic model with rate constants of 0.01156 (BC-Fe) and 0.02063 g/mg·min (Z-Fe) was the best fit for adsorption. Thermodynamic studies revealed that the adsorption is spontaneous and endothermic with an increase in randomness at the solid–liquid interface. [ABSTRACT FROM AUTHOR]

The study aimed at firstly preparing two eco-friendly biomaterials of PFeS&PEB and PFeS&WAB from peanut shells biochar (PEB) and walnut shells biochar (WAB) by loading with ferrous sulfide powder (Powder-FeS) to evaluate the ability to remove Pb(II) from sewage. FeS was immobilized to the surfaces biochar through functional groups such as –OH, –COOH and C–O. The results of batch experiments showed that PFeS&PEB had the maximum adsorption capacity (98.039 mg·g–1) when pH = 5 and the dosage was 0.75 g·L–1. The adsorption data were adequately simulated with adsorption kinetics and isothermal thermodynamic analysis, suggesting that the adsorption of Pb(II) by PFeS&PEB and PFeS&WAB was mainly monolayer chemisorption, and the adsorption process was spontaneous endothermic. The removal of Pb(II) was achieved by the association of complexation, redox, ion exchange, electrostatic attraction and physical adsorption. Reusability studies showed that PFeS&PEB and PFeS&WAB had good stability over four consecutive cycles. Hence, the cost-effective materials of PFeS&PEB and PFeS&WAB can be used as effective bio)adsorbent for the removal Pb(II) from wastewater. [ABSTRACT FROM AUTHOR]

The adsorption of commercial glyphosate on biochar (BC) and oxidized biochar (BCox) from corn cob was studied thoroughly to characterize in detail the behavior of these adsorbent materials. Kinetic, isothermal and thermodynamic tests were performed in both materials using Brunauer-Emmett-Teller surface area analysis, accelerated surface area and porosimetry, Fourier-transform infrared spectroscopy, Barrett-Joyner-Halenda pore size and volume analysis, X-ray diffraction and scanning electron microscopy techniques. Adsorption equilibrium occurred in 60 min with an adsorption capacity of 0.58 mg⋅g-1 (22.3%) for BC and 1.49 mg⋅g-1 (53.2%) for BCox, with the latter showing a higher adsorption rate in the initial stage, reaching a 44% removal in the first 5 min, while in the case of BC, the removal was 5%. The pseudo-first-order kinetic model better adjusted to both adsorbents, although in the case of oxidized biochar, the Avrami model suggested that adsorption can also occur according to the pseudo-second-order model. Experimental data fitted in Langmuir and Freundlich isotherms revealed a more accurate fitting with the Freundlich model. The thermodynamic analysis showed that the adsorption of glyphosate was an endothermic and nonspontaneous phenomenon in this study. Acid oxidation with H3PO4 produced smaller pores and caused the collapse of the porous structure of the adsorbent. The results also showed that although acid oxidation enhanced the adsorption of commercial glyphosate, the values were considered low when compared with those obtained for pure compound s presented in the literature. [ABSTRACT FROM AUTHOR]

In this paper, air-dried lake sludge was pretreated by ball milling, and then pyrolysed at 600°C to prepare lake sludge-derived ball milling biochar, and Fe3O4 was loaded on lake sludge-derived ball milling biochar by chemical precipitation. Scanning electron microscopy-energy-dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, and X-ray diffraction were used to investigate and characterize the adsorbents. The results demonstrated that ball mill pretreatment and Fe3O4-loaded can effectively increase the content of O-containing groups in the adsorbent. The batch adsorption experiments revealed that Cd(II) removal followed the pseudo-secondorder kinetic model and the Langmuir model. Additionally, the Cd(II) maximum adsorption by biochar (BC), MBBC and Fe3O4@MBBC was 31.33, 47.36 and 92.42 mg/g, respectively. The Cd(II) removal mechanisms were complexation, ion exchange, co-precipitation and electrostatic interaction. The Cd(II) removal efficiency on Fe3O4@MBBC was maintained at 91.35% after 5 adsorption--desorption experiments, indicating that Fe3O4@MBBC had the ability to be better applied for the removal of Cd(II)-containing wastewater. [ABSTRACT FROM AUTHOR]

Tunnel wash water has been repeatedly reported to contain higher volume of pollutants, but its treatment is not legally bounded in many countries of EU and elsewhere. In this study, three samplings of tunnel wash water were carried out during 2019 and 2020. First sampling determined the chemical pollutants and helped to design the experimental tunnel wash water treatment. Second and third samplings were analysed and later treated in glasses filter pre-tests using 4 different adsorbents. As adsorbent were used food waste biochar, activated food waste biochar, wooden biochar and as the conventional absorbent of granulated activated carbon as a control. The glasses pre-tests focused on determination appropriate contact time and amount of adsorbent. Analyses were focused on organic and inorganic pollutants contained in tunnel wash water. The results of the analysis included undissolved substances, C10-C40 hydrocarbons, chlorides, sulfates, heavy metals, and other chemical elements. The analyses showed that biochar had comparable effect on pollutants reduction such as granulated activated carbon. The adsorption had mainly effect on reducing concentration of toxic metals especially Zn (94.7%) and Cu (50.8%). The highest level of reduction was measured for Fe (98.0%). On contrary the results of tensides, sulfates and some of chemical elements showed small or none effect. For better reducing of all pollutants must precede another level of treatment. The results showed that adsorption on the filter medium could be one of treatment processes, and cheaper biochar represents an eco-friendly way of treatment tunnel wash water, which belongs among the important strategies of circular economy. [ABSTRACT FROM AUTHOR]