Modified Pine Sawdust Research Articles

Pretreatment of Biogas Slurry by Modified Biochars to Promote High-Value Treatment of Wastewater by Microalgae

High concentrations of contaminants such as ammonia nitrogen and organic matter in full-strength wastewater severely inhibit the growth of microalgae, contributing to lower biomass accumulation and contaminant removal efficiency. To overcome this limitation, modified biochars prepared from pine sawdust and sugarcane bagasse were used in this study as an adsorbent–desorbent for the pretreatment of wastewater to promote the growth of microalgae. The results showed that the two modification methods (acid/alkaline modification and magnesium salt modification) used in the experiment could increase the abundance of oxygen-containing functional groups. Moreover, magnesium salt modification could effectively improve the pore structure of biochar surfaces and increase the specific surface areas. Compared with the pristine biochars, the adsorption performance of the modified biochar was found to be significantly higher for nutrients in wastewater. The adsorption capacity of the acid/alkaline-modified pine sawdust biochar reached 8.5 and 16.49 mg∙g−1 for ammonia nitrogen and total organic carbon in wastewater, respectively. The magnesium salt modified pine sawdust biochar achieved a more comprehensive nutrients adsorption capacity of 15.68, 14.39, and 3.68 mg∙L−1 for ammonia nitrogen, total organic carbon, and total phosphorus, respectively. The mechanism of ammonia nitrogen adsorption was mainly the complexation of surface -OH functional groups, while the adsorption mechanism for phosphate was mainly the complexation of -OH and Mg-O functional groups and the chemical precipitation of MgO or Mg(OH)2 attached to the surface.

Adsorption of bisphenol A and 2,4-dichlorophenol onto cetylpyridinium chloride-modified pine sawdust: a kinetic and thermodynamic study.

Using biomass wastes as adsorbents is a promising option for organic waste reclamation, but unfortunately, their adsorption capacity is usually limited, especially for hydrophobic organic pollutants. To address this issue, this work prepared cetylpyridinium chloride (a cationic surfactant)-modified pine sawdust (CPC-PS) and further demonstrated their performance for hydrophobic bisphenol A (BPA) and 2,4-dichlorophenol (DCP) adsorption. Compared to the PS, the CPC-PS improved the maximum adsorption capacity for BPA and DCP by approximately 98% and 122%, respectively. The kinetic and thermodynamic analyses showed that the BPA and DCP adsorption onto the CPC-PS fitted the pseudo-second-order kinetics and the Freundlich model. After regeneration using NaOH, the adsorption capacity of the CPC-PS for BPA still maintained 80.2% of the initial value after five cycles. Based on the experimental results, the CPC-PS was proposed to enhance the BPA and DCP adsorption through the solubilization of hemimicelles for hydrophobic organic pollutants, the π-π stacking between benzene-ring structures, and the hydrogen binding between the adsorbents and the pollutants. This work provides a viable method to use surfactant-modified pine sawdust as effective adsorbents to remove hydrophobic pollutants.

WATER PURIFICATION WITH NATURAL SORBENTS

Industrial waste can be considered as technological and economical raw materials in related industries, and their disposal in compliance with environmental legislation can be environmentally efficient. Nowadays, researchers search for an effective but relatively cheap absorption material to extract various contaminants from water. Of great greatest interest are the industrial waste that can be used in wastewater treatment technology as a secondary raw material. As a rule, active coals are used in drinking water systems and deep wastewater treatment. In the Tyumen region, this type of sorbent is quite expensive, since there are no natural coal deposits. The sawdust sorbent is proposed to applied as fuel briquettes. The sorption properties of the modified pine sawdust in relation to oil products are studied herein. The correlation analysis is carried out for each type of sorbent exposure. The solution regression and correlation coefficients are calculated. The obtained equations of regression are used to construct absorption isotherms characterizing the dependence of sorption capacity on the concentration of petroleum products in the solution. The sorption activity of sawdust increases by 1.4–4 times depending on the type of modification and intensification. It is shown that the total exchange capacity of pine sawdust on the model solution is only 19.4% lower than the that of activated carbon, which is very expensive for the Tyumen region. In the case of sawdust used for water purification, two environmental problems are solved simultaneously: cheap and effective cleaning of oil-saturated surface runoff and recycling of wood waste.

Enhanced adsorption and photo-degradation of bisphenol A by β-cyclodextrin modified pine sawdust in an aquatic environment

The occurrence of bisphenol A (BPA) raised significant concerns about potential adverse impacts on environmental health, and its removal has become a hot research topic. We conducted batch adsorption and photo-degradation experiments to determine the removal performance of BPA by β-cyclodextrin (β-CD) modified pine sawdust (CD-PS) in an aquatic environment for the first time. Pine sawdust (B-PS) was treated by NaOH firstly and then modified by β-CD. The adsorption behaviour of BPA on the B-PS and CD-PS were observed to follow Langmuir and pseudo-second-order kinetic models, and that CD-PS had a 1.2 times higher adsorption capacity than B-PS. At 25 °C and pH=7.0, the maximum adsorption capacity of CD-PS reached 0.0319mmol/g. Moreover, the effects of β-CD, CD-PS and B-PS on the photo-degradation of BPA were compared under UV irradiation, indicating that CD-PS significantly enhanced the removal efficiency. Additionally, the “saturated” CD-PS could be regenerated several times using UV irradiation without loss during BPA adsorption process. Results of this work demonstrate that β-CD immobilized on the surface of CD-PS could be acted as an excellent catalyst for BPA removal, and a possible reactive mechanism was further proposed in this regards. These observations indicate that the CD-PS system can remediate BPA-polluted aquatic environment very well.

Fluoride removal by aluminum-modified pine sawdust: Effect of competitive ions

The removal of fluoride from aqueous solutions by pine sawdust chemically modified with aluminum in batch systems was investigated. The loading process of aluminum in this biomaterial was achieved by the hydrolysis of metal salts. The kinetics andsorption capacities of the unmodified and modified pine sawdust were evaluated. The effect of different parameters such initial fluoride concentration, pH and contact time was studied on the sorption process. Since the presence of other ions may affect the sorption of fluoride, some studies of binary or multiple systems have simulated a real natural water effluent. The aim of this study was the evaluation of competitive ions in the sorptionof fluoride using pine sawdust in fluoride (F−) single systems and F−/HCO3− and F−/SO42− binary systems. Batch-type contact experiments were performed to evaluate the kinetics and equilibrium fluoride sorption, all at 25°C, 100rpm and pH values adjusted to 6, 7 and 8 depending on the conditions of the binary or single systems. It was found that the Lagergren model described the F− sorption kinetic data and the Langmuir and Freundlich equations described the equilibria of the sorption binary systems. These results suggested that the sorption mechanism was chemisorption on a heterogeneous material. The pH effects governing sorption capacities were also evaluated, showing a decrease as pH value rises, indicating that this sorption process is highly pH-dependent. The physical characterization of the biosorbent after fluoride removal by infrared analyses showed fluoride removal in different functional groups on the surface of the modified and unmodified biosorbents. The point of zero charge and co-existing ions affected the efficiency of defluoridation significantly. The pine sawdust showed a high affinity for fluoride ions compared with conventional adsorbents; therefore, it can be considered as a good low cost biosorbent for the defluoridation of water.

Synthesis of highly porous zinc–carbon composites based on modified pine wood

Highly porous materials containing zinc oxide were prepared form modified pine wood. The growth dynamics of zinc oxide microcrystallites in the course of carbonization of pine sawdust mixed with ZnCl2 was studied. The hexagonal wurtzite-type ZnO phase is formed at 400°С and is broken down at approximately 800°С. The synthesized composite material has a high specific surface area, up to 1900 m2 g–1. The relationships of the porous structure formation in the composite in relation to the temperature and subsequent treatment with water were revealed. Opening of the porous structure of the composite in the course of carbonization of modified pine sawdust is associated with the formation of crystal-like phases of carbon and ZnO.

Vanadium(V) removal from aqueous solution and real wastewater using quaternized pine sawdust.

Cross-linked and quaternized pine sawdust was tested for vanadium removal from a synthetic aqueous solution as well as from real industrial wastewater which had a considerable amount of vanadium and other ions such as sulphate, ammonium and nickel. The maximum vanadium sorption capacity of the modified pine sawdust was found to be 130 mg/g in synthetic solution and 103 mg/g in real wastewater. Modified pine sawdust worked well over a wide range of pH. Column studies with real wastewater proved that vanadium was efficiently desorbed from the material with 2 M NaOH and that the material could be reused.

Adsorption of Divalent Heavy Metal Ions from Aqueous Solution by Citric Acid Modified Pine Sawdust

Removal of certain divalent heavy metal ions (Cu2+, Pb2+, and Cd2+) from aqueous solutions by citric acid modified pine sawdust (CA-PS) was investigated in this study. The contribution of the citric acid modification to the increase of adsorption capacity of metal ions is significant. In the mono-component system of Cu2+, the maximum adsorption capacity of CA-PS (0.253 mmol/g or 16.19 mg/g) is more than three times higher than that of B-PS (0.079 mmol/g or 5.06 mg/g). The adsorption kinetics and isotherm of the pretreated pine sawdust (B-PS) and CA-PS can be well elucidated with the pseudo-second order model and the Langmuir model, respectively. The competitive adsorption behavior of Cu2+, Cd2+, and Pb2+ in the binary systems (Cu2++Pb2+, Cu2++Cd2+, and Pb2++Cd2+) were studied, and the preference of adsorption onto CA-PS can be ordered as Pb2+ > Cu2+ > Cd2+. The results showed the possibility of utilizing natural bio-sorbent as cost-effective adsorbent alternative for heavy metal ions removal.

Removal of nitrate by modified pine sawdust: Effects of temperature and co-existing anions

The effect of temperature, sulphate and phosphate, and the initial nitrate concentration on nitrate removal was studied with synthetic solutions. Chemically modified pine sawdust (Pinus sylvestris) anion exchange resin (MPSD) was used in the sorption studies. The resin was synthesized by reacting pine sawdust with epichlorohydrin, ethylenediamine and triethylamine in the presence of N,N-dimethylformamide. Nitrate removal was successful at 5–70 °C. Higher temperatures caused nitrate removal to decrease moderately, but sorption capacities of 22.2–32.8 mg/g for NO3–N were achieved. The removal of nitrate in the presence of sulphate or phosphate was studied at concentrations of 30 mg N/l, 10–500 mg S/l and 1–50 mg P/l. A significant decrease in nitrate reduction was observed at sulphate and phosphate concentrations of 100 mg S/l and 50 mg P/l, respectively. The effect of initial nitrate concentration was studied in column. Nitrate sorption was clearly dependent on the initial concentration. Desorption of nitrate in column was completed using about 80 bed volumes of 0.1 M NaCl solution. The sorption data were fitted to the Langmuir, Freundlich and Redlich–Peterson adsorption models. The Redlich–Peterson and Langmuir models gave the best fit, which suggests monolayer sorption. Thermodynamic studies revealed that the sorption of nitrate was spontaneous and exothermic in nature. The results imply that modified pine sawdust could be a feasible alternative in the treatment of real industrial wastewaters.

Preparation of novel anion exchangers from pine sawdust and bark, spruce bark, birch bark and peat for the removal of nitrate

Novel anion exchangers were prepared from pine (Pinus sylvestris) sawdust and bark, spruce (Picea abies) bark, birch (Betula pubescens/Betula verrucosa) bark and peat for the removal of nitrate (NO3−). Chemical modification was applied by means of epichlorohydrin, ethylenediamine and triethylamine in the presence of N,N-dimethylformamide (DMF). The materials were characterized in terms of elemental composition (C, H, N and O), chemical composition, BET surface area, FT-IR spectra and FESEM. Nitrogen (NO3−–N) removal efficiency (%) was used as a performance indicator for the anion exchangers. Modified pine sawdust exhibited the best nitrate removal efficiency. Over 80% of NO3−–N was removed at doses of >3g/l with a NO3−–N concentration of 30mg/l. The removal efficiency of modified pine sawdust remained unchanged at pH 3–10. Maximum sorption capacities of 24.2–30.1mg/g were achieved for NO3−–N, which were very good compared to the literature values and to a commercial anion exchange resin. The sorption was very rapid and the linearized pseudo-second order kinetic model fitted the data well. The sorption data were best fitted in the linearized Langmuir model. Modified pine sawdust was tested in column as well, where it maintained its ion exchange ability well for five ion exchange cycles including successful desorption cycles.

Characterization of modified sawdust, kinetic and equilibrium study about methylene blue adsorption in batch mode

Methylene blue (MB) biosorption by citric acid modified pine sawdust (Pinus tabulaeformis) was studied from aqueous solutions. Batch experiments were conducted to determine the biosorption properties of the biomass. The Langmuir isotherm equation could fit the equilibrium data. The maximal equilibrium quantity of MB from Langmuir model was 111.46 mg g �1 at 293 K. The Elovich model adequately described the kinetic data in comparison to the pseu- do-first-order model and pseudo-second-order model; the process involving rate-controlling step is very complex in- volving both boundary layer and intra-particle diffusion processes. The effective diffusion parameter Di and Df values were estimated at different initial concentration, and the average values were determined to be 5.76×10 �8 and 2.12× 10 �7 cm 2 s �1 . Thermodynamic parameters showed that the adsorption of methylene blue onto pine sawdust biomass was feasible, spontaneous and endothermic under studied conditions. The physical and chemical properties of the bio- sorbent were determined by SEM, TG-DSC, XRD, and the point of zero charge (pHpzc) and the nature of biomass-dye interactions were evaluated by FTIR analysis, which showed the participation of COOH, OH and NH2 groups in the biosorption process. Biosorbents could be regenerated using 0.01 mol L �1 HCl solution at least three cycles, with up to 90% recovery. Thus, the biomass used in this work proved to be effective for the treatment of MB bearing aqueous solutions.

Chemically Modified Biosorbent for Phosphorus Removal from Aqueous Solution

In the present study, chemically modified Aleppo pine (Pinus halepensis Miller) sawdust was used for removal of phosphate from water. Biosorbent preparation process included size fractionation, extraction for surface activation, acid prehydrolysis, and treatment with urea. Sorption of phosphate ions onto biosorbent was studied using the batch technique. The effect of different parameters such as contact time, adsorbate concentration, and temperature was investigated. The adsorption kinetics data were best described by the pseudo-second-order rate equation, and equilibrium was achieved after 40 min. The Langmuir and Freundlich equations for describing adsorption equilibrium were applied to data. The constants and correlation coefficients of these isotherm models were calculated and compared. The adsorption isotherms obey the Freundlich equation. The thermodynamic parameters like free energy, enthalpy and entropy changes for the adsorption of phosphate ions have been evaluated and it has been found that the reaction was spontaneous and endothermic in nature. The low value of activated energy of adsorption, 3.088 kJ/mol, indicates that the phosphate ions are easily adsorbed on the sawdust. Results suggest that the prepared chemically modified Aleppo pine sawdust has potential in remediation of contaminated waters by phosphate

ARSENATE BIOSORPTION BY IRON-MODIFIED PINE SAWDUST IN BATCH SYSTEMS: KINETICS AND EQUILIBRIUM STUDIES

The biosorption of As(V) from aqueous solutions by pine sawdust chemically modified with iron in batch systems was investigated. The loading process of Fe in this biomaterial was achieved by hydrolysis of two different ferric salts. This modification of sawdust is an attempt to improve As(V) biosorption for practical applications. The kinetics and maximum biosorption capacities of the unmodified and modified pine sawdust were evaluated. It was found that the pseudo-second order model described the As(V) biosorption kinetic data and the Langmuir-Freundlich equation described the arsenate sorption equilibrium. These results indicated that the sorption mechanism was chemisorption on a heterogeneous material. The pH effects governing biosorption capacities were also evaluated, showing a decrease as pH value rises, indicating that this biosorption process is highly pH-dependent. The estimated maximum biosorption capacities of As(V), based on the Langmuir-Freundlich fit to the data were, at pH 4, 4.4 mg/g of untreated sawdust, (UN-SW), 12.85 mg/g of ferric chloride modified sawdust (FeCl-SW), and 6 mg/g of ferric nitrate modified sawdust (FeNit-SW); and at pH 7, 2.6 mg/g of UN-SW, 5.9 mg/g of FeCl-SW, and 4.6 mg/g of FeNit-SW. Sorption capacities of iron-modified pine sawdust were evidently higher than other similar biosorbents previously reported.

Wastewater Treatment for Dyes and Heavy Metals Using Modified Pine Sawdust as Adsorbent

Abstract The main objective of this study was to evaluate the feasibility of removing hexavalent chromium and methylene blue, taken as representative species for heavy metals and dyes, respectively, from aqueous solutions, using industrial by-products, specifically pine sawdust, which comes ample in Greece and from many sources. The material was tested in raw form and after acid hydrolysis treatment under mild conditions. Adsorption experiments were carried out to investigate the effects of adsorbent dose, pH, contact time and initial adsorbent concentration, on the adsorption process. The adsorption kinetics and adsorption equilibrium were further studied using the data obtained from these experiments.

Removal of uranium(VI) from aqueous solution using citric acid modified pine sawdust: batch and column studies

This study described adsorption of uranium(VI) by citric acid modified pine sawdust (CAMPS) in batch and fixed-bed column modes at 295 K. The equilibrium adsorption data were analyzed by Langmuir, Freundlich, Koble–Corrigan and Dubinin–Radushkevich isotherm models. The results indicated that the Langmuir and Koble–Corrigan models provided the best correlation of the experimental data. The Elovish model was better to fit the kinetic process, which suggested that ion exchange was one of main mechanism. The effective diffusion parameter Di values indicated that the intraparticle diffusion was not the rate-controlling step. In fixed-bed column adsorption, the effects of bed height, feed flow rate, and inlet uranium (VI) concentration were studied by assessing breakthrough curve. The Thomas, the Yan and the bed-depth/service time (BDST) models were applied to the column experimental data to determine the characteristic parameters of the column adsorption. The results were implied that CAMPS may be suitable as an adsorbent material for adsorption of uranium (VI) from an aqueous solution.

Fungal removal of gaseous hexane in biofilters packed with poly(ethylene carbonate) pine sawdust or peat composites

The removal of volatile organic compounds (VOC) in biofilters packed with organic filter beds, such as peat moss (PM) and pine sawdust (PS), frequently presents drawbacks associated to the collapse of internal structures affecting the long-term operation. Poly(ethylene ether carbonate) (PEEC) groups grafted to these organic carriers cross linked with 4,4'-methylenebis(phenylisocyanate) (MDI) permitted fiber aggregation into specific shapes and with excellent hexane sorption performance. Modified peat moss (IPM) showed very favorable characteristics for rapid microbial development. Water-holding capacity in addition to hexane adsorption almost equal to the dry samples was obtained. Pilot scale hexane biofiltration experiments were performed with the composites after inoculation with the filamentous fungus Fusarium solani. During the operation of the biofilter under non-aseptic conditions, the addition of bacterial antibiotics did not have a relevant effect on hexane removal, confirming the role of fungi in the uptake of hexane and that bacterial growth was intrinsically limited by an adequate performance of the composites. IPM biofilter had a start-up period of 8-13 days with concurrent CO(2) production of approximately 90 g m(-3) h(-1) at day 11. The final pressure drop after 70 days of operation was 5.3 mmH(2)O m(-1) reactor. For modified pine sawdust (IPS) packed biofilter, 5 days were required to develop an EC of about 100 g m(-3) h(-1) with an inlet hexane load of approximately 190 g m(-3) h(-1). Under similar conditions, 12-17 days were required to observe a significant start-up in the reference perlite biofilter to reach gradually an EC of approximately 100 g m(-3) h(-1) at day 32. Under typical biofiltration conditions, the physical-chemical properties of the modified supports maintained a minimum water activity (a(w)) of 0.925 and a pH between 4 and 5.5, which allowed the preferential fungal development and limited bacterial growth.