Phenol adsorption on biochar prepared from the pine fruit shells: Equilibrium, kinetic and thermodynamics studies

Biochar and GAC intensify anaerobic phenol degradation via distinctive adsorption and conductive properties

The roles of biochar and granular activated carbon (GAC) in the enhancement of anaerobic phenol degradation were characterized through batch tests conducted at different phenol concentrations, coupled with adsorption kinetics, microbial community, and in-situ electrochemical analysis. Both biochar and GAC (15 g/L) led to markedly shorter lag times (t₀) by adsorbing dissolved phenol, and faster maximum CH₄ production rate (R_max) by triggering direct interspecies electron transfer (DIET) during a two-stage (adsorption then degradation) anaerobic phenol degradation. The high adsorption capacity of GAC helped achieve a shorter t₀, but less affected R_max of subsequent phenol degradation. Compared with GAC, which showed higher conductivity but no redox activity, biochar exhibited higher electron exchange capacity (6.57 μmol e^-/g). This higher electron exchange capacity stemmed from the diverse redox-active moieties, which resulted in a more efficient DIET. Meanwhile, the formation of wire-like appendages which linked the enriched DIET partners (such as Syntrophorhabdus and Methanosaeta) on biochar probably futher enhanced the electron transfer. However, hydrogenotrophic methanogenesis was still the main pathway for syntrophic phenol degradation in the suspended sludge. The in-situ analysis also confirmed that biochar and GAC acted as geobatteries and geoconductors, respectively, and that the stimulation of DIET was persistent.

Engineered biochar from wood apple shell waste for high-efficient removal of toxic phenolic compounds in wastewater

This study investigated a novel agricultural low-cost bio-waste biochar derived from wood apple fruit shell waste via the pyrolysis method, which is modified by ball milling and utilized to remove toxic phenol and chlorophenols (4-CPh and 2,4-DCPh) from contaminated aqueous media. The ball-milled wood apple fruit shell waste biochar (WAS-BC) sorbent was systematically analyzed by BET, CHN, and FTIR as well as particle size, SEM-EDS, XPS and TGA studies. The sorption equilibrium and kinetic studies exhibit that the sorption capacity was greater than 75% within the first 45 min of agitation at pH 6.0. The uptake capacity of 2,4-DCPh onto WAS-BC was greater than those of 4-CPh and phenol. Equilibrium results were consistent with the Langmuir isotherm model, while the kinetic data were best represented by the Elovich and pseudo-second-order model. The maximum uptake of phenol, 4-CPh, and 2,4-DCPh was 102.71, 172.24, and 226.55 mg/g, respectively, at 30 ± 1 °C. Thus, this study demonstrates that WAS-BC is an efficient, low-cost sorbent that can be used for the elimination of phenol and chlorophenol compounds from polluted wastewater.

An Overview and Evaluation of Highly Porous Adsorbent Materials for Polycyclic Aromatic Hydrocarbons and Phenols Removal from Wastewater

Polycyclic aromatic hydrocarbons (PAHs) and phenolic compounds had been widely recognized as priority organic pollutants in wastewater with toxic effects on both plants and animals. Thus, the remediation of these pollutants has been an active area of research in the field of environmental science and engineering. This review highlighted the advantage of adsorption technology in the removal of PAHs and phenols in wastewater. The literature presented on the applications of various porous carbon materials such as biochar, activated carbon (AC), carbon nanotubes (CNTs), and graphene as potential adsorbents for these pollutants has been critically reviewed and analyzed. Under similar conditions, the use of porous polymers such as Chitosan and molecularly imprinted polymers (MIPs) have been well presented. The high adsorption capacities of advanced porous materials such as mesoporous silica and metal-organic frameworks have been considered and evaluated. The preference of these materials, higher adsorption efficiencies, mechanism of adsorptions, and possible challenges have been discussed. Recommendations have been proposed for commercialization, pilot, and industrial-scale applications of the studied adsorbents towards persistent organic pollutants (POPs) removal from wastewater.

How Photocatalyst Dosage and Ultrasound Application Influence the Photocatalytic Degradation Rate of Phenol in Water: Elucidating the Mechanisms Behind

Photocatalysis is of high interest for the treatment of wastewater containing non-biodegradable organic components. In this work, the photocatalytic degradation of phenol by TiO2 photocatalysis was assessed, the influence of ultrasound (US) treatment was evaluated, and the mechanisms behind it were elucidated. It was shown that the TiO2 concentration (in suspension) has a large influence on the degradation kinetics. At high TiO2 concentrations, a reduced efficiency was observed due to the shielding of the UV light by TiO2 particles. US treatment effectively increased phenol degradation by improving the mass transfer while it was shown by the experimental data that particle deagglomeration did not play a significant role. The degradation mainly occurred through indirect phenol oxidation by hydroxyl (OH*) radicals, which were formed in situ at the surface of the photocatalyst. Finally, based on the partial least squares (PLS) methodology, a mathematical model was developed, representing phenol degradation as a function of the selected process conditions.

Removal of phenolic compounds from aqueous solution using MgCl2-impregnated activated carbons derived from olive husk: the effect of chemical structures

Activated carbon (BC) prepared from olive oil solid waste (olive husk) by slow pyrolysis was chemically activated using MgCl₂ (BC-MgCl₂). The BC and BC-MgCl₂ were used as adsorbents for removal of three phenolic compounds, namely, phenol (P), p-methoxyphenol (PMP) and p-nitrophenol (PNP), from aqueous solution. The uptake of these three phenolic compounds by the BC and BC-MgCl₂ was better expressed by the Langmuir and Dubinin-Radushkevich (D-R) isotherm models than by the Freundlich isotherm, and the kinetics of the adsorption process followed the pseudo-second order kinetic model. The maximum monolayer adsorption capacity of P, PMP and PNP were increased from 24.938, 45.455 and 61.728 on BC to 43.860, 98.039 and 121.951 mg/g on BC-MgCl₂ by factors of 1.76, 2.16 and 1.98, respectively. Therefore, the chemical activation of BC by MgCl₂ is indeed of importance for improving its adsorption performances. For both adsorbents, the adsorption phenomenon for different substituted phenols is a strong function of solubility, polarity, molecule structure, and size. At the tested temperatures (25, 35 and 45 °C), the negative values of ΔG° and positive values of ΔH° and ΔS° for the adsorption of P, PMP and PNP on BC and BC-MgCl₂ demonstrated that the adsorption was a spontaneous, endothermic and entropy-increasing process.

Biochar for Wastewater Treatment—Conversion Technologies and Applications

Biochar as a stable carbon-rich material shows incredible potential to handle water/wastewater contaminants. Its application is gaining increasing interest due to the availability of feedstock, the simplicity of the preparation methods, and their enhanced physico-chemical properties. The efficacy of biochar to remove organic and inorganic pollutants depends on its surface area, pore size distribution, surface functional groups, and the size of the molecules to be removed, while the physical architecture and surface properties of biochar depend on the nature of feedstock and the preparation method/conditions. For instance, pyrolysis at high temperatures generally produces hydrophobic biochars with higher surface area and micropore volume, allowing it to be more suitable for organic contaminants sorption, whereas biochars produced at low temperatures own smaller pore size, lower surface area, and higher oxygen-containing functional groups and are more suitable to remove inorganic contaminants. In the field of water/wastewater treatment, biochar can have extensive application prospects. Biochar have been widely used as an additive/support media during anaerobic digestion and as filter media for the removal of suspended matter, heavy metals and pathogens. Biochar was also tested for its efficiency as a support-based catalyst for the degradation of dyes and recalcitrant contaminants. The current review discusses on the different methods for biochar production and provides an overview of current applications of biochar in wastewater treatment.

Removal of methylene blue from aqueous solutions by biochar prepared from the pyrolysis of mixed municipal discarded material

This paper investigates the adsorption of organic compounds in aqueous solution to biochar adsorbent, using methylene blue as an indicator for adsorption. Biochar was produced by the pyrolysis of mixed municipal discarded material in an innovative heat pipe reactor, the pyrolysis temperature was held at 300°C for 12 h. Biochar produced under these conditions was found to have oxygen containing functional groups that are beneficial to the adsorption of methylene blue as well as graphitic structures suggesting potential sites for π-π interactions with methylene blue. Methylene Blue followed the pseudo second order kinetic model with higher R² values than both the pseudo first order kinetic and intraparticle diffusion models. The adsorption also closely fit the Langmuir isotherm rather than the Freundlich model, suggesting monolayer adsorption rather than multilayer adsorption. Maximum adsorption capacity was observed at 7.2 mg/g for initial concentration of 100 mg/l Methylene blue in aqueous solution. The amount of Methylene blue adsorbed increased with increasing initial concentration as expected. The adsorption mechanisms are likely π-π interactions between methylene blue and the graphitic structures in the biochar which are shown to be present in Raman spectroscopy, as well as electrostatic attraction and ionic bonding between negatively charged surface sites on the char and the positive charge on the dissolved methylene blue molecules. The results show that biochar obtained from mixed waste could be employed as a low-cost and effective tool in water treatment for the removal of basic dyes and potentially other organic impurities.

Preparation, characterization, and application of magnetic activated carbon for treatment of biologically treated papermaking wastewater

In view of the urgent need for tertiary treatment of papermaking wastewater and the difficulty in separating powdered activated carbon (PAC) from water, the magnetic activated carbon (33%-MPAC, 50%-MPAC and 67%-MPAC) were prepared by chemical coprecipitation method for adsorption of biologically treated papermaking wastewater (BTPW). A series of characterization of MPAC and PAC were carried out and show that the content of iron oxides is negatively related to the proportion of micropores in MPAC. The loaded iron oxides is mainly the mixture of magnetite and maghemite, and the maximum saturation magnetization of MPAC can reach 29.68 emu/g. Batch mode experiments were performed, and found that the adsorption effect of MPAC is slightly worse than that of PAC, the adsorption capacity of COD in MPAC can reach about 65 mg/g, and pH = 2 and 10 °C are more favorable for adsorption. The adsorption isotherms and kinetics were well fitted by the Freundlich model and pseudo-second-order kinetic model, respectively. The selective adsorption was studied by using the excitation emission matrix (EEM) fluorescence spectrum and high-performance size exclusion chromatography (HPSEC). It is concluded that all adsorbents are preferred to adsorb humic acid-like substances (HA). And all adsorbents are preferred to adsorb low apparent molecular weight substances (LAMW, AMW < 1500 Da), with the increase of iron oxides content, the phenomenon of MPAC preferentially adsorbed LAMW became less obvious.

Synthesis of mesoporous magnetic polypyrrole and its application in studies of removal of acidic, neutral, and basic pharmaceuticals from aqueous medium

As an alternative to traditional adsorbents, mesoporous magnetic polypyrrole (MMPPy) was first used as an adsorbent for the removal of acid, neutral, and basic pharmaceutical compounds considered aqueous pollutants. Ibuprofen (IBU, acid), caffeine (CAF, neutral), and bupropion (BUP, basic) were chosen as adsorbates and applied in adsorption studies. They proved to be pH dependent of the aqueous solution and the best results were found at pH 4 for IBU and CAF and pH 7 for BUP and 60 mg was the optimal amount of adsorbent to be used in the studies. Adsorption was extremely fast and the equilibrium was reached up to 180 s. The adsorption data of all analytes could be well interpreted by the pseudo second-order kinetic model and the dual-site Langmuir-Freundlich isotherm model. The adsorption capacities obtained by the dual-site Langmuir-Freundlich model were 53.67 mg g^-1, 16.74 mg g^-1, and 24.72 mg g^-1 for IBU, CAF, and BUP, respectively. Thermodynamic parameters revealed that IBU adsorption becomes spontaneous as temperature increases and CAF and BUP adsorption occurs through a non-spontaneous process. In addition, this study shows endothermic nature of the adsorption process. Analytes were desorbed using an aqueous solution at pH 10 for IBU, pH 7 for CAF, and pH 4 for BUP and then the material was regenerated successfully. The results suggest that MMPPy can be efficiently used in the removal of different organic analytes found in contaminated water.

Simultaneous extraction of permethrin diastereomers and deltamethrin in environmental water samples based on aperture regulated magnetic mesoporous silica

The aperture of KIT-6 can influence the recoveries of magnetic solid phase extraction.

Potential application of chicken manure biochar towards toxic phenol and 2,4-dinitrophenol in wastewaters

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 (q_max) of Ph and DNP were found at 106.2 and 148.1 mg g^-1, respectively. The obtained q_max 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.

Enhanced fluoride removal from water by rare earth (La and Ce) modified alumina: Adsorption isotherms, kinetics, thermodynamics and mechanism

The removal of F^- from aqueous solution using lanthanum and cerium modified mesoporous alumina (La/MA and Ce/MA) was studied, and characteration of the adsorbents by XRD, BET, XRF, FTIR, TEM, XPS and the pH_ZPC measurements were carried out. The adsorption was investigated in both batch and column adsorption systems. Batch experimental results showed that adsorption capacities of adsorbents were recorded in the following order: La/MA > Ce/MA > mesoporous alumina (MA). Besides, adsorption datas were fitted well by Sips isotherm model and Elovich kinetics model, and the maximum adsorption capacity of La/MA was 26.45 mg·g^-1 in Sips model at the dosage of 2.0 g·L^-1 and near neutral condition (pH = 6.0 ± 0.1). Moreover, thermodynamic parameters were illustrated that adsorption process of fluoride ion over La/MA was spontaneous and endothermic. In the adsorption process, the interaction between metal and fluoride, the adsorption capacity was increased due to form the bond of M···F (M = La or Ce). Furthermore, the influence of coexisted anions on F^- removal was investigated, and it was indicated that removal efficiency was slightly affected by the presence of Cl^- and NO₃^-, while SO₄^2- and CO₃^2- caused a sharp fall in removal efficiency. Column experiments results were indicated that time of break-through of La/MA was twice as much as that of MA.

Synthesis of carbon nanotubes using biochar as precursor material under microwave irradiation

Biochar is a carbon-rich porous material obtained by the thermochemical treatment of biomass. Biochar presents a suitable composition as precursor material for carbon nanotubes (CNTs) growth, and can be used as a sustainable alternative in the valorization of biomass. In this study, the synthesis of CNTs using biochar as biological precursor material is presented. CNTs were synthesized using a mixture of biochar and ferrocene including microwave assisted heating. Biochar samples used in the synthesis of CNTs were obtained from agroindustrial waste such as wheat straw, oat hulls, rapeseed cake and hazelnut hulls pyrolyzed at 400 °C and 600 °C. Synthesized CNTs were examined by dynamic light scattering, UV-VIS spectroscopy, Raman spectroscopy and transmission electron microscopy. The results indicate that the physicochemical properties of CNTs were influenced by pyrolysis temperature of biomass. Biochars obtained at 600 °C produced higher CNTs concentration and smaller hydrodynamic diameter. Moreover, CNTs synthesized from biochar of hazelnut hulls and wheat straw show a higher degree of wall graphitization, suggesting superior CNT quality. The results of this study show the feasible production of CNTs using biochar as precursor material.

Editorial: Technically-based use of by-products as a tool to control pollution

This Virtual Special Issue of Journal of Environmental Management dealt with the recycling of waste and by-products, focusing on their use in controlling environmental pollution. The field of research was previously considered as promising, in view of its relevance and the increasing number of papers published in last years. And this Special Issue allows going a step ahead in the matter, with 90 submissions and a number of 48 high quality papers finally accepted and published. We think that it will be useful at a global level, especially for researchers, social partners, and social actors involved in environmental and public health issues related to environmental pollution.

BP-ANN Model Coupled with Particle Swarm Optimization for the Efficient Prediction of 2-Chlorophenol Removal in an Electro-Oxidation System

Electro-oxidation is an effective approach for the removal of 2-chlorophenol from wastewater. The modeling of the electrochemical process plays an important role in improving the efficiency of electrochemical treatment and increasing our understanding of electrochemical treatment without increasing the cost. The backpropagation artificial neural network (BP-ANN) model was applied to predict chemical oxygen demand (COD) removal efficiency and total energy consumption (TEC). Current density, pH, supporting electrolyte concentration, and oxidation-reduction potential (ORP) were used as input parameters in the 2-chlorophenol synthetic wastewater model. Prediction accuracy was increased by using particle swarm optimization coupled with BP-ANN to optimize weight and threshold values. The particle swarm optimization BP-ANN (PSO-BP-ANN) for the efficient prediction of COD removal efficiency and TEC for testing data showed high correlation coefficient of 0.99 and 0.9944 and a mean square error of 0.0015526 and 0.0023456. The weight matrix analysis indicated that the correlation of the five input parameters was a current density of 18.85%, an initial pH 21.11%, an electrolyte concentration 19.69%, an oxidation time of 21.30%, and an ORP of 19.05%. The analysis of removal kinetics indicated that oxidation-reduction potential (ORP) is closely correlated with the chemical oxygen demand (COD) and total energy consumption (TEC) of the electro-oxidation degradation of 2-chlorophenol in wastewater.

An ionic liquid functionalized polymer for simultaneous removal of four phenolic pollutants in real environmental samples

An ionic liquid functionalized polymer (IL-P) was prepared feasibly and simply by grafting1-butyl-3-vinylimidazolium bromide onto the silica surface. The IL-P was fully characterized, and the results showed that IL-P has a rough surface with a lower specific surface area (205.49 m² g^-1), and the involvement of ionic liquid significantly improved the adsorption performance of IL-P. The pH, initial concentration, adsorption time and temperature were investigated to discuss the adsorption behaviors of IL-P in aqueous solution. The adsorption process of 2,4-dichlorophenol (2,4-DCP), bisphenol A (BPA) and 2,4-dinitrophenol (2,4-DNP) onto IL-P better fitted the pseudo-second-order model, while that of 2-isonaphthol (2-NP) followed the pseudo-first-order model. The adsorption behaviors of IL-P towards 2,4-DCP and 2,4-DNP fitted well with Liu isotherm model, and that of BPA and 2-NP can be described by Langmuir model. The maximum adsorption capacities of 2,4-DCP, BPA, 2,4-DNP and 2-NP bound on IL-P was 239.7, 68.39, 56.86 and 64.28 mg g^-1, respectively, and the adsorption of IL-P is a spontaneous physical process. Comparing with other adsorbent, the as-prepared IL-P showed excellent recognition ability towards the phenolic compounds and can be applied to adsorb and remove trace 2,4-DCP, 2-NP, 2,4-DNP and BPA simultaneously in complicated wastewater and soil samples.

Adsorption Characteristics of Phenolic Compounds on Graphene Oxide and Reduced Graphene Oxide: A Batch Experiment Combined Theory Calculation

A series of phenolic compounds containing 2-phenylphenol (PPE), bisphenol A (BPA), 4-isopropylphenol (IPE), 4-methylphenol (ME) and phenol (PE) were selected to investigate their major influence factors for their adsorption on graphene oxide (GO) and reduced graphene oxide (RGO) by studying their adsorption isotherms and kinetics. It was found that the adsorption of all tested phenols fitted well with the Freundlich model. In comparison, the adsorption ability of RGO with a stronger π-π interaction was superior to GO, which was confirmed by using naphthalene probe measurements. The thermodynamic characteristics, by studying the effect of the adsorption temperatures (298, 313 and 333 K), demonstrated that the adsorption process was spontaneous, exothermic and entropy-decreasing. The chemical structures of the phenols also affected their adsorption on GO and RGO. It was found that the adsorption capacities of phenols were, in order, PE (0.271 mmol g−1 on GO and 0.483 mmol g−1 on RGO) < ME (0.356 and 0.841 mmol g−1) < IPE (0.454 and 1.117 mmol g−1) < BPA (0.4 and 1.56 mmol g−1) < PPE (0.7 and 2.054 mmol g−1), which depended on the π-electron density of the benzene ring by means of a density functional theory (DFT) calculation. Undoubtedly, the reduction of GO and an increase in π-electron density on the chemical structures of phenols facilitated the adsorption.