Synthesis and characterization of slow pyrolysis pine cone bio-char in the removal of organic and inorganic pollutants from aqueous solution by adsorption: Kinetic, equilibrium, mechanism and thermodynamic

Performance and dynamic modelling of biochar and kaolin packed bed adsorption column for aqueous phase methylene blue (MB) dye removal

A practical continuous adsorption study in a packed-bed column was conducted by using two separate layers of kaolin and pine cone based biochar packed bed adsorbents for the removal of methylene blue (MB) dye from its aqueous solution. A series of column experiments were performed to determine the breakthrough curves (BTCs) by varying bed height (3-7 cm), inlet flow rate (13-17 ml/min) and initial dye concentration (50-150 mg/L). The Thomas, Yoon-Nelson, Bed Depth Service Time (BDST) and Dose response (DR) dynamic models were applied to column experimental data under various operational conditions to predict the column breakthrough curves (BTC) using both nonlinear regression and linear regression and to determine various characteristic parameters such as percentage removal of dye, breakthrough time, used bed length, mass transfer zone (MTZ) and dye adsorption density q_(total) that are useful for process design. The MB dye adsorption was found to be most favourable under low flow rate, high adsorbent bed height and high initial dye concentrations. The experimental column breakthrough data were in good agreement with the various dynamic models and the results of various model characteristic parameters could be used to scale up the process to an actual industrial column operation. Also, this column study revealed the feasibility of pine cone biochar and kaolin adsorbents as alternative sustainable adsorbents for dye-bearing wastewater treatment.

Preparation of biochar with high absorbability and its nutrient adsorption-desorption behaviour

To study the formation of biochar with high absorbability, experiments were carried out at different carbonization temperature (300, 400, 600, and 800 °C) and under different carbonization atmosphere (activating gases (steam and CO₂) and inert gas (N₂)) to prepare biochar. In this paper, the effects of the carbonization atmosphere on the biochar pore structure were studied, and the influence of the biochar pore structure on the adsorption-desorption behaviour of nutrients (NH₄⁺-N, NO₃^--N, P, and K) was investigated. Experimental results: (1) The activating gases (steam and CO₂) can catalytically crack activated carbon atoms and tar blocking the biochar pores at high temperatures (T > 600 °C), and the activating gas promotes the formation of microporous biochar (d < 2 nm). (2) Micropores with a pore diameter distribution of 0.6-2 nm in biochar have the strongest nutrients adsorption, and pores with a diameter below 0.6 nm cannot adsorb hydrated ions of nutrients. (3) Biochar prepared at 600 °C and CO₂ atmosphere has the best adsorption effect on nutrients. The adsorption kinetic was well described by Pseudo-second-order model. (4) After 5 cycles of biochar, the adsorption of the nutrients is still >40% of the first adsorption. Biochar has relatively high reusability.

Advances in production and application of biochar from lignocellulosic feedstocks for remediation of environmental pollutants

Thermochemical processing of biomass results in a producing char, a typical by-product. The char can be termed as biochar when specifically applied as a soil fertility enhancement. Biochar, when utilized efficiently, is basic for enhancing financial viability and also to maintain ecosystem. The properties of carbonized biomass rely upon raw materials (feedstock) and procedure conditions. Biochar shows an incredible potential to effectively handle water contaminants taking into consideration the wide accessibility of feedstock, suitable physical/chemical surface properties and low-cost. Pyrolysis technology for converting lignocellulosic biomass into biochar has emerged as a frontier research domain for the removal of pollutants. This review focused on production of biochar from various sources of lignocellulosic biomass (cellulose, hemicellulose and lignin) and its application in various fields such as agriculture, wastewater treatment process. Biochar is a significant resource however, its application require further examination of its properties and structure and techniques to alter those factors.

A novel Fe3O4/graphene oxide/citrus peel-derived bio-char based nanocomposite with enhanced adsorption affinity and sensitivity of ciprofloxacin and sparfloxacin

To create more active adsorption sites on biochar, the Fe₃O₄/GO/citrus peel-derived magnetic bio-nanocomposite (mGOCP) with hierarchically porous architectures was synthesized by a facile one-pot hydrothermal approach for efficient removal of fluoroquinolone antibiotics ciprofloxacin (CIP) and sparfloxacin (SPA). The characterization analysis of bio-nanocomposites showed that the incorporation of GO could ensure relatively higher surface area (1556 cm² g^-1), more abundant pore structure, and higher thermal stability within mGOCP bio-nanocomposites than Fe₃O₄/citrus peel-derived magnetic bio-nanocomposites (mCP). And the mGOCP-1% attained outstanding adsorption capacity for CIP (283.44 mg g^-1) and SPA (502.37 mg g^-1), respectively. The primary adsorption mechanisms for CIP and SPA included π-π electron donor-acceptor interaction, H-bonding, hydrophobic interaction and electrostatic interaction. Overall, the surface morphology and structural composition of biochars could be regulated with GO to facilitate the adsorption capacity. Moreover, the developed mGOCP could be extended as a potential adsorbent for removal of other emerging organic pollutants in water.

Multivariate analysis and multiple linear regression as a tool to estimate the behavior of hexazinone in Brazilian soils

Weed control efficiency and the environmental contamination potential of herbicides depend on soil sorption and desorption. Among the indexes that evaluate the soil adsorption processes, the coefficients sorption (Kf_s) and desorption (Kf_d) obtained by Freundlich isotherms can provide accurate information about the behavior of an herbicide in the soil. The values of Kf_s and Kf_d of an herbicide vary according to the physicochemical characteristics of the soil, so it is possible to estimate these coefficients with high precision if good predictive mathematical models are constructed. Therefore, our objective aimed to evaluate the use of multiple regression models (MLR) associated with multivariate techniques to estimate the coefficient Kf_s and Kf_d for the hexazinone based on the chemical and physical attributes of soils. The correlation analyses, principal components, and clustering analysis allowed the multiple linear regression technique to generate models with higher adjustment coefficient (R²) for Kf_s (0.73 to 0.99) and Kf_d (0.94 to 0.99), and lower root mean squared error (RMSE) for Kf_s (0.003 to 0.065) and Kf_d (0.018 to 0.120). Regression models created from groups of soils showed greater prediction performance for Kf_s and Kf_d. The organic matter followed by the cation exchange capacity was the most important attributes of soils in sorption and desorption processes of hexazinone.

Thermal conversion of pineapple crown leaf waste to magnetized activated carbon for dye removal

Pineapple crown leaf was successfully converted to the magnetized activated carbon (MAC) as an attractive solution to overcome separation problems. The activated carbon (AC) was produced by an innovative method combining KOH activation and microwave heating while the magnetization process was prepared by a co-precipitation method. In this sense, the activation stage was studied at different impregnation ratio. The resulted magnetic adsorbent was further tested its feasibility for methyl violet dye removal. The result shows that MAC consists of both micropores and mesopores with more oxygen-containing functional groups, indicating it can be used to remove dye from contaminated water. The increase of impregnation ratio led to an increase in the MAC porosity and a decrease in the magnetic property. The adsorption behavior of methyl violet dye onto MAC was well described by the Redlich-Peterson isotherm model.

A promising form-stable phase change material prepared using cost effective pinecone biochar as the matrix of palmitic acid for thermal energy storage

A promising new form-stable phase change material (PA/PB) was fabricated using pinecone biochar (PB) as the supporting material of palmitic acid (PA). The biochar of PB with large surface area was produced by forest residue of pinecone, and it was cheap, environment friendly and easy to prepare. The PB was firstly utilized as the supporter of PA and the characterizations of PA/PB were analyzed by the BET, SEM, XRD, DSC, TGA, FT-IR and thermal conductivity tester. The results demonstrated that the PA was physically absorbed by the PB and the crystal structure of the PA was not destroyed. The results of DSC showed that the fusing and crystallization points of the form-stable phase change material with the maximum content of PA (PA/PB-4) were 59.25 °C and 59.13 °C, and its fusing and freezing latent heat were 84.74 kJ/kg and 83.81 kJ/kg, respectively. The results of TGA suggested that the thermal stability of the PA/PB-4 composite was excellent, which could be used for the applications of thermal energy storage. Furthermore, the thermal conductivity of PA/PB-4 was 0.3926 W/(m∙K), which was increased by 43.76% compared with that of the pure PA. Thus, the study results indicated that the PA/PB-4 had great potential for thermal energy storage applications.

A method for particulate matter 2.5 (PM2.5) biotoxicity assay using luminescent bacterium

The ability to analyze biotoxicity of atmospheric pollution plays an important role in public health. It provides the potential to directly analyze the health information of at-risk individuals. Although air quality standards have received significant attention in many countries, the potential for better biotoxicity assessment has remained largely unexplored. Here we propose a method using one kind of luminescent bacterium Photobacterium phosphereum to detect the biotoxicity of atmospheric particulate matter ≤ 2.5 µm (PM_2.5). Combined with the results of air pollution data of the year 2013-2014, this method has been proven to have good biotoxicity detection performance, and can evaluate the severity of at least 85% of PM_2.5 related biotoxicity in Shanghai during this time period. Based on an established algorithm of this detection system, the biotoxicity of twelve PM_2.5 real samples (collected over a month) were tested and divided into different biotoxicity levels. It allows an effective evaluation of biotoxicity of PM_2.5 due to the quick and sensitive response of bioluminescence to the concentration of toxic components, which provides a valuable reference to evaluate the biotoxicity of PM_2.5. This established method can be easily applied to the analysis and evaluation of any other PM_2.5 samples assay by following the steps.

Removal Efficiency and Mechanism of Cr(VI) from Aqueous Solution by Maize Straw Biochars Derived at Different Pyrolysis Temperatures

The removal efficiency and mechanism of Cr(VI) removal from aqueous solution on semi-decomposed maize straw biochars pyrolyzed at 300 to 600 °C were investigated. The removal of Cr(VI) by the biochars decreased with pyrolysis temperature increasing from 300 to 600 °C, and the maximum removal capacity of Cr(VI) for maize straw biochar pyrolyzed at 300 °C was 91 mg/g at pH 2.0. The percentage removal of Cr(VI) rapidly decreased with pH increasing from 2.0 to 8.0, with the maximum (>99.9%) at pH 2.0. The variation of Cr(VI) and Cr(III) concentrations in the solution after reaction showed that Cr(VI) concentration decreased while Cr(III) increased and the equilibrium was reached after 48 h, while the redox potential after reaction decreased due to Cr(VI) reduction. X-ray photoelectron spectroscopy (XPS) semi-quantitative analysis showed that Cr(III) accounted for 75.7% of the total Cr bound to maize straw biochar, which indicated reductive adsorption was responsible for Cr(VI) removal by the biochars. Cr(VI) was firstly adsorbed onto the positively charged biochar surface and reduced to Cr(III) by electrons provided by oxygen-containing functional groups (e.g., C=O), and subsequently part of the converted Cr(III) remained on the biochar surface and the rest released into solution. Fourier transform infrared (FTIR) data indicated the participation of C=O, Si–O, –CH2 and –CH3 groups in Cr(VI) removal by the biochars. This study showed that maize straw biochar pyrolyzed at 300 °C for 2 h was one low-cost and efficient adsorbent for Cr(VI) removal from aqueous solution.

Feasibility of industrial-scale treatment of dye wastewater via bio-adsorption technology

This review emphasizes the importance of costs in industrial-scale treatment of dye wastewater and provides a way to assess the cost-based feasibility of bio-adsorption technologies. Dye wastewater is one of the major contributors to environmental pollution. Bio-adsorption has attracted considerable attentions in dye wastewater treatment due to its technical feasibility, flexibility and operation simplicity. However, industrial-scale treatment of dye wastewater via bio-adsorption technologies remains stagnant, mainly due to high costs. So far, no review or research articles have systematically discussed the criteria for successful utilization of bio-adsorption technologies on a large scale. This review discusses the major factors affecting adsorption and desorption performance based on basic chemical and physical structures of bio-adsorbents available in literatures. A quantitative relationship has been summarized based on previous studies to assess the cost to utilize a bio-adsorption technology and serve as an access threshold for quality bio-adsorbents to be taken into real applications.

Decolorization of cationic and anionic dye-laden wastewater by steam-activated biochar produced at an industrial-scale from spent mushroom substrate

The feasibility of producing biochar and its steam-activated counterpart in a large scale (1000 kg) from spent mushroom substrate (SMS) and their usage as effective environmental remediation tools to augment current SMS management strategies were explored. Steam-activated SMS biochar exhibited enhanced surface area (332 m²/g), pore volume (0.29 cm³/g), and porosity (77.1%). The effectiveness of activation was higher on the cationic dye, crystal violet (CV) by 4.1 times increase from 255 mg/g to 1057 mg/g. The biochar and its steam-activated counterpart, respectively exhibited high COD and color removal efficiencies of 49.6% and 40.1%, and 67.7 and 99.6% for CV-spiked real wastewater. Reusability studies confirmed the dominant role of chemisorption in the adsorption process. The lower production cost coupled with the superior physicochemical properties and adsorption performances rendered the biochar with/without steam activation, as a promising alternative adsorbent to serve as a green, viable and effective environmental remediation tool.

Enhanced phosphate adsorption on Ca-Mg-loaded biochar derived from tobacco stems

Tobacco stems were used as precursors to prepare biochars (YGs) and develop Ca-Mg-loaded biochars (CMYGs) to enhance phosphate adsorption from aqueous solutions. Some influencing factors, such as pH, adsorption time, temperature, and structure characterization, were investigated. Fourier transform infrared (FTIR) spectra and X-ray diffraction (XRD) patterns showed several new peaks, indicating that Mg(OH)2 and MgO have been present on the surface of the CMYGs. The adsorption could reach equilibrium in 100 min reaction. The equilibrium data were well described by the Langmuir and Freundlich model. After five recycles, the phosphate removal capacity of CMYGs biochar retained over 50%. Moreover, the XRD and FTIR analyses showed that the phosphate sorption mechanisms involved surface electrostatic attraction, inner-sphere complexation and precipitation reactions. Overall, the soaking method could be used to effectively load Mg2+ onto the surface of YGs. The CMYGs synthesized at 750 °C is a promising adsorbent for phosphate removal with a high adsorption capacity for phosphate-polluted wastewater.

Facile low-temperature one-step synthesis of pomelo peel biochar under air atmosphere and its adsorption behaviors for Ag(I) and Pb(II)

This study prepared a novel low-cost surface functionalized carbon adsorbent (PPC) from biomass waste (pomelo peel) through a facile low-temperature (250 °C) one-step method under regular air atmosphere. The adsorption performance and mechanism of the carbon material for Ag(I) and Pb(II) were investigated by a range of sorption experiments and characterizations including SEM, EDX, XRD and FTIR. Sorption experimental results suggested that PPC had high adsorption capacities of 137.4 and 88.7 mg/g for Ag(I) and Pb(II), respectively, with adsorbent dosage of 2 g/L at unadjusted solution pH and room temperature (23 ± 1 °C). The characterization results indicated high-efficiency removal of the heavy metals by PPC was attributed to the strong chemical adsorption involving that Ag(I) ions were reduced as metallic Ag particles by oxygenic functional groups and Pb(II) ions were precipitated as Pb₅(PO₄)₃OH crystals by phosphorous functional groups on the carbon surfaces. This study provides the possibility of synthesis high-efficient adsorbent using economic and environmental-friendly approach with low energy consumption.

Cost-Effective Biochar Produced from Agricultural Residues and Its Application for Preparation of High Performance Form-Stable Phase Change Material via Simple Method

A new form-stable composite phase change material (PEG/ASB) composed of almond shell biochar (ASB) and polyethylene glycol (PEG) was produced via a simple and easy vacuum impregnation method. The supporting material ASB, which was cost effective, environmentally friendly, renewable and rich in appropriate pore structures, was produced from agricultural residues of almond shells by a simple pyrolysis method, and it was firstly used as the matrix of PEG. Different analysis techniques were applied to investigate the characteristics of PEG/ASB, including structural and thermal properties, and the interaction mechanism between ASB and PEG was studied. The thermogravimetric analysis (TGA) and thermal cycle tests demonstrated that PEG/ASB possessed favorable thermal stability. The differential scanning calorimetry (DSC) curves demonstrated that the capacities for latent heat storage of PEG/ASB were enhanced with increasing PEG weight percentage. Additionally, PEG/ASB had an excellent thermal conductivity of 0.402 W/mK, which was approximately 1.6 times higher than that of the pure PEG due to the addition of ASB. All the study results indicated that PEG/ASB had favorable phase change properties, which could be used for thermal energy storage.

In situ surface decoration of Fe3C/Fe3O4/C nanosheets: Towards bi-functional activated carbons with supercapacitance and efficient dye adsorption

This work reports a bi-functional activated porous carbon (PC) prepared from a biomass tofu, with excellent capacities for charge storage and adsorption of organic dyes, which is enabled by decorating with Fe₃C/Fe₃O₄/C nanosheets. The in-situ growth and self-assembly of the nanosheets on the carbon surface are achieved by a one-step catalytic carbonization of tofu simultaneously with FeCl₃ and ZnCl₂ catalysts. Due to the high surface area and unique iron compounds-containing and sheet-like structures, the PCs exhibit an electrochemical capacitance of 315 F g^-1 at 0.5 A g^-1 as supercapacitor electrodes, and an ultrahigh adsorption capacity of 918 mg g^-1 for methylene blue (MB) and 868 mg g^-1 for Rhodamine B (RhB). This study provides a new perspective for understanding the effects of surface engineering on increasing charge storage and dye adsorption ability of biomass-derived PCs as well as for developing bi-functional PCs with novel magnetic properties.

Activated biochar derived from pomelo peel as a high-capacity sorbent for removal of carbamazepine from aqueous solution

In recent years, the application of biochar to remove contaminants from aqueous solutions has become interesting due to favorable physical/chemical properties and abundant feedstocks.