Acid Washing Pretreatment Research Articles

Coupling weak magnetic field and zero-valent iron-activated persulfate oxidation process activation for improving dewaterability of waste activated sludge

Zero-valent iron (ZVI) activated persulfate (S2O82−) oxidation offers an alternative strategy for enhancing sludge dewatering. However, the slow corrosion/dissolution and precipitations of oxide iron layer of ZVI particles limit it real applications. In this study, weak magnetic field (WMF) was coupled with zero-valent iron (ZVI)-activated persulfate (S2O82−) oxidation at the different initial pH levels to enhance waste activated sludge (WAS) dewatering ability. The use of WMF can avoid the precipitation of ferric (hydr) oxides and accelerate the dissolution of ZVI particles, with the concentration of Fe(II) increased from 10.0 ± 8.8 to 222.0 ± 118.0 mg/L. The lowest CST/CST0 value of 0.27 ± 0.00 was observed at the ZVI/S2O82− dosage of 1.5/1.2 mmol/g-VS when coupled with WMF of 25 mT, lower than that without WMF (0.59 ± 0.03). The improved ZVI corrosion and subsequent liberation of Fe(II) provoked the SO4−· production from S2O82− and thus enhanced the sludge dewaterability greatly by disrupting the extracellular biopolymers and cells. Our results show that the application of WMF can be feasible for ZVI/S2O82− oxidation to improve sludge dewatering performance. ZVI/S2O82− oxidation cannot only avoid rapid free radical consumption and introduction of other anions to a certain extent, but also is more environmentally friendly when coupled with WMF than with thermal and acid-wash pretreatment.

Optimizing process parameters in water- and acid-washing pretreatment of rice straw

Optimizing process parameters in water- and acid-washing pretreatment of rice straw

Effects of inherent AAEMs on catalytic gasification of biomass with large particle size under oxygen-steam atmosphere

Oxygen-steam gasification of biomass is a promising technology because of its ability to improve syngas quality and reduce energy consumption. In this study, a fixed-bed reactor is employed to assess the effects of inherent alkali and alkaline earth metals (AAEMs) on the catalytic gasification of candlenut wood with large particle size under the oxygen-steam atmosphere. Two grain directions, radial and axial, are considered for candlenut wood. Various characterization techniques, SEM, X-ray CT, BET, and FTIR, are employed to analyze biochar samples. GC-MS and GC are determined to tar and syngas respectively. The results show that char yield from biomass with axial grain is higher. Acid-washing removes alkali metals (K and Na) better from biomass with axial grain than radial grain, and vice versa for alkaline earth metals (Ca and Mg). In terms of the gasified chars derived from acid-washed biomass, AAEMs content gradually decreases along the end surface and radial direction, which could also be observed from the 3D reconstruction of X-ray CT images. In all samples, micropores (0–10 µm) dominate and are distributed along the grain direction. In general, pores of 20–30 µm and above 30 µm comprise a minor proportion. Inherent AAEMs facilitate an augmentation in char yield as well as BET and total pore volume of gasified char. AAEMs and grain direction have a slight effect on functional groups of gasified chars. Certain organic matter species and content in tar are remarkably affected by the grain direction, since the discrepancies of pore structure and specific surface area. Acid-washing pretreatment augments the content and organic species of M2-M4 compounds (containing 2–4 benzene rings) in the tar. K and Na significantly boost the char steam gasification, water-gas shift, and steam-tars reforming reactions. A decrement in concentrations of H2 (14.49% and 13.35%), CH4 (0.51% and 0.89%), and CO2 (2.32% and 1.37%) in syngas derived from acid-washed samples are acquired, respectively, compared to that of biomass samples with radial and axial grains. However, a reduction of 4.09% and 1.53% in syngas calorific value could be obtained. The CnHx volume fraction is significantly affected by grain direction and AAEMs, with axial grain yielding a higher volume fraction of C2H4 (49.07%), C2H2 (71.29%), and C3H8 (127.36%) from acid-washed sample than that of radial grain.

Thermochemical conversion of neem seed biomass to sustainable hydrogen and biofuels: Experimental and theoretical evaluation

This study aims to investigate the potential of neem seeds as a renewable energy source for producing bio-oil and syngas through both experimental and theoretical approaches. Neem seeds underwent thermal pyrolysis in a semi-batch reactor after undergoing acid wash pre-treatment. The effects of pyrolysis temperatures (350–550 °C) and heating rates (10–40 °C/min) on product yields were analyzed, and the highest achieved bio-oil yield was 60.2 % at 450 °C and a heating rate of 40 °C/min. In the theoretical section, the Aspen Plus software was employed to simulate the process of steam gasification of neem seeds to identify optimal operating conditions for maximizing hydrogen production and cold gas efficiency (CGE) while maintaining an ideal H2/CO ratio. By analyzing the impact of operating parameters such as steam-to-biomass (S/B) ratio and temperature on the composition of the syngas stream, H2/CO ratio, and CGE, the study determined that the optimal operating conditions are an S/B ratio of 0.9 and temperatures ranging from 650 to 750 °C. The findings of this study can shed light on the potential of neem seed as a non-edible biomass source for renewable energy production, which can help reduce greenhouse gas emissions and mitigate the negative impacts of traditional energy sources on the environment.

Influence of alkali and alkali earth metals on pyrolysis of tobacco waste

The effect of alkali and alkali earth metals on pyrolysis behavior of tobacco was revealed in this paper. Four alkali and alkali earth metal ions (Na+, K+, Ca2+, and Mg2+) were used to impregnate acid-washed tobacco. The addition of alkali and alkali earth metal ions in acid-washed tobacco increases the relative content of ketones, acids, nitrogen containing compounds, and esters, while inhibit the formation of anhydro sugars and aldehydes. The generation of solid residues is enhanced by the presence of alkali and alkali earth metal ions and the increase of K+ concentration. The addition of 0.5 mmol K+/g can increase the yield of solid residues from 13.7 wt% to 20.2 wt%. The increase of K+ concentration promotes the conversion of anhydro sugars to ketones. The effect of hot water-wash, acid-wash, and acid-infuse, which can control the concentration of alkali and alkali earth metal ions in the tobacco, on the product distribution of tobacco pyrolysis were also discussed. Acid-wash method and hot water-wash method promote the production of carbohydrate derivatives and inhibit the generation of nitrogen-containing products. After nitric acid-wash and hot water-wash pretreatment, the relative content of nitrogen-containing products decreased from 52.1% to 6.2% and 4.3%, respectively. Compared with inorganic acid-wash pretreatment method, organic acid-wash pretreatment method has weaker inhibition on nitrogen-containing products. Organic acid-wash pretreatment method promoted the formation of aromatics and aldehydes. Prewash methods facilitate the thermal decomposition of tobacco. The results from this study suggests that feedstock pretreatment could be used as a strategy of controlling aroma compounds formation from tobacco.

Preparation of bio-oil enriched with phenolic compounds by combining acid-washing pretreatment and condensation technology

The cooperative interaction of acid-washing pretreatment and condensation technology was used to explore the experiment of phenolic compounds enrichment by pyrolysis of cotton straw. The bio-oil was synthetically analyzed from functional group composition, pyrolysis properties and critical composition. The percentage of condensable fraction in pyrolytic organic vapors was remarkably improved after the acid-washing pretreatment. The condensation technology promoted the selective condensation of pyrolytic organic vapors, separated small molecules such as acetic acid and water, and facilitated the enrichment of phenolic substances. With the cooperative interaction of acid-washing pretreatment and condensation technology, the moisture in bio-oil was diminished by 55.81%, the content of acetic acid dropped from 14.15 wt% to 5.70 wt%, and the total detectable phenolic compounds rose from 1.41 wt% to 7.07 wt%. This investigation offered a facile and useful optimization scheme to concentrate high-value-added phenolic compounds by pyrolytic liquefaction of biomass.

Effect of water/acetic acid washing pretreatment on biomass chemical looping gasification (BCLG) using cost-effective oxygen carrier from iron-rich sludge ash

Effect of water/acetic acid washing pretreatment on biomass chemical looping gasification (BCLG) using cost-effective oxygen carrier from iron-rich sludge ash

Experimental and simulation study of peanut shell-derived activated carbon and syngas production via integrated pyrolysis-gasification technique

Carbonaceous materials are among the most appropriate and widely used materials in the field of energy production, conversion, and storage. According to recent studies, biochar-based catalytic supports and adsorbents have shown great potential in the fields of energy production and the adsorption and storage of various gases due to their adjustable surface chemistry and porosity. In the present study, the pyrolysis of peanut shell to produce activated carbon as a precursor for catalyst support was investigated. Acid washing pretreatment was performed on raw biomass before pyrolysis to remove metals and impurities and reduce the ash content of the biomass. Before pyrolysis, thermogravimetric analysis was performed to determine the temperature range of biomass thermal decomposition. Pyrolysis was carried out at temperatures of 300, 400, and 500 °C to study the effect of pyrolysis temperature on biochar yield. KOH-activation on biochar was followed by subsequent pyrolysis at 650 °C to produce activated carbon. To study the effect of pyrolysis temperature and KOH activation on the structural and physiochemical characteristics of biochar, nitrogen adsorption/desorption and FTIR analyses were conducted. The pore size of the activated carbon surface changed from mesoporous to microporous with increasing the pyrolysis temperature and subsequent KOH activation, and the biochar specific surface area increased from 3.5 to 363.1 m2 g-1. In order to evaluate and optimize the operating conditions of the biochar and syngas production processes on larger scales, the integrated pyrolysis and gasification processes were simulated in Aspen Plus software. The effects of temperature, pressure, and air to biomass ratio on biochar production rate and H2/CO ratio were evaluated. A temperature of 650 °C, a pressure of 1 bar and an air to biomass ratio of 0.1 were selected as optimum operating conditions to simultaneously achieve maximum biochar production and maintain the quality of synthetic gas. The findings of the experimental and simulation sections of this study could provide a useful guide for the industrial-scale production of biochar and activated carbon as a catalytic support in various chemical production processes, as well as a water polutant adsorbent and gas adsorbent for various gas purification and storage processes.

Soot and gaseous product formation characteristics of leached high-alkali lignite pyrolysis at a high temperature

The contents of alkali and alkaline earth metals (AAEMs) in Zhundong lignite are very high, which can affect the formation of soot during coal combustion process. In this study, the effect of leaching treatment on soot and gaseous product formation characteristics from the lignite pyrolysis at 1300 ℃ is investigated. The results show that water washing only removes a small amount of water-soluble AAEMs, which has little impact on the combustion characteristics of the coal, while acid washing pretreatment largely removes Na, Mg, Ca and other ash components, causing obvious ignition delay. The acid washing obviously leads to the deterioration of oxidation characteristics and increases the yield of pyrolytic soot, and the peak diameter of soot increases from 100 nm to 200 nm. Moreover, after both water- and acid-leaching, more CO2 is produced, while CH4, CO, and H2 are reduced. The yields of C2H4 are not changed before and after leaching. However, a certain amount of C2H2 is produced for acid-leached coal pyrolysis. These phenomena indicates that there may be different soot generation and evolution paths in three cases. To a certain extent, this provides a theoretical guidance for the research of effectively reducing soot emissions and improving coal utilization under high-temperature pyrolysis.

Volatile-char interactions during biomass pyrolysis: Effect of biomass acid-washing pretreatment

The purpose of this study is to investigate the effect of acid-washing pretreatment on the poplar wood (PW) pyrolysis under different volatile-char interactions, the experiment was conducted in a self-designed fixed-bed pyrolysis reactor. It was found that acid-washing pretreatment could alter the surface morphology of PW, increase the cellulose crystallinity and reduce the inorganic ash components (mainly Alkali and Alkaline Earth Metal species, AAEMs). AAEMs acted as catalysts for sugar ring fragmentation and charring reactions during both primary pyrolysis of biomass and secondary volatile-char interactions. The removal of AAEMs would increase the bio-oil yield and decrease the biochar and non-condensable gas yields, same trend was also observed with the decreasing volatile-char interactions. The removal of AAEMs and weakened volatile-char interactions both resulted in an increase of C content and a decrease of O content of biochar with more pore structures generated, especially micropores, the content of anhydrosugars in bio-oil was also largely enhanced. In addition, the decrease of volatile-char interactions would significantly reduce the effect of AAEMs in biomass on the pyrolysis process. A highest bio-oil yield of 63.37 wt% with 34.38% of anhydrosugars could be obtained even for a packed fixed-bed reactor by intentionally reducing volatile-char interactions and removing AAEMs from biomass during the process.

Synergistic enhancement of bio-oil quality through hydrochloric or acetic acid-washing pretreatment and catalytic fast pyrolysis of biomass

Peanut shells were used as raw materials, and the synergistic effects of various acid pretreatments and catalytic pyrolysis for biomass were comprehensively studied. The results showed that the oil yield of 0.5 mol/L hydrochloric acid treatment was 44.75 wt%, and that of 0.5 mol/L acetic acid treatment was 43.40 wt%. The solid products decreased apparently after pretreatment. Acid-washing pretreatment and the subsequent catalytic pyrolysis of the pretreated biomass promoted the yield of aromatic in bio-oil. The yield of bio-oil gradually decreased while the gas yield increased with the increase of catalytic pyrolysis temperature. Ketones and anhydrosugars were also reduced in the bio-oil, while aromatics increased significantly, reaching the highest value of 19.62 wt% (0.5 mol/L hydrochloric acid treatment) and 19.30 wt% (0.5 mol/L acetic acid treatment) respectively at 600 ℃. Synergy effect facilitated the conversion of pyrolytic intermediates to gas and aromatics. Besides, the possible formation mechanism of bio-oil under different pyrolysis conditions is proposed. The study indicates the optimized combination could effectively improve the quality of bio-oil.

Improvement of wheat (T. aestivum) straw catalytic fast pyrolysis for valuable chemicals production by coupling pretreatment of acid washing and torrefaction

The present work investigated the coupling pretreatment of acid washing and torrefaction to address secondary cracking of target products and condensation of intermediates and improved bio-oil quality and hydrocarbon selectivity of the catalytic fast pyrolysis (CFP) process. The total hydrocarbon yields in CFP increased from 28.06 wt% to 55.31 wt% by torrefaction and 46.29 wt% by coupling pretreatment. The acid washing resulted in fewer acids and phenols and more sugars in bio-oil by decreasing the AAEMs. The removal rate of the potassium was up to 96.7 %, and other elements were above 83 %. Torrefaction elevated the C/O ratio and the higher calorific value of biomass. It could also decrease the acid content in obtained bio-oil in the CFP process. In addition, the TG/TGA results showed that higher torrefaction temperature decreased the total weight loss of biomass. Meanwhile, the acid washing pretreatment improved the resolution of the two pyrolysis peaks of the DTG curve. These results showed that the AAEMs removal and intermediates inhibition could elevate the selectivity of the valuable chemical. • Acid washing removed 83 wt% of AAEMs to facilitate valuable chemicals conversion; • Torrefaction elevated the C/O ratio and the higher calorific value of wheat straw; • The coupling pretreatment improved bio-oil quality and hydrocarbons selection; • The CFP with pretreated biomass reduced phenols, acids, and ketones production.

Comparative assessment of water and organic acid washing pretreatment for nitrogen-rich pyrolysis: Characteristics and distribution of bio-oil and biochar

Nitrogen-containing compounds are important organic compounds that can be produced in large quantities by the nitrogen-rich pyrolysis of biomass. The aim of this study was to investigate the effect of washing pretreatment on the yield and selectivity of nitrogen-containing compounds during corn cob nitrogen-rich pyrolysis in a fixed-bed reactor. Water and organic acids were used for washes. Urea was used as the exogenous nitrogen source in nitrogen-rich pyrolysis at 500 °C. After washing pretreatment, bio-oil derived from nitrogen-rich pyrolysis had the highest yield (44.9%) and lowest water content (26.3%) and acidity. The resulting bio-oil contained a few types of compounds. Water washing improved the selectivity of pyrrole, pyridine, imidazole, and nitrile. Organic acid washing promoted the production of pyridone and imidazolinone in nitrogenous heterocyclic compounds, especially 2(1H)-pyridinone, the content of which reached 7.48%. Biochar derived from nitrogen-rich pyrolysis contained abundant nitrogenous functional groups, and the stability of biochar was optimal after washing pretreatment. Therefore, washing pretreatment could enhance the production of high-value nitrogen-containing chemicals during nitrogen-rich pyrolysis.

Development of Ni-doped Fe/Ca catalyst to be used for hydrogen-rich syngas production during medicine residue pyrolysis

In this work, the catalytic pyrolysis of herbal residues (HR) by Ni–Fe/Ca catalysts and the effects of intrinsic ash and heating rate on the activity of Ni–Fe/Ca catalysts were investigated in a fixed-bed reactor. The results showed that the strong interaction of Fe and Ca formed Ca2Fe2O5, which inhibited the formation of CaCO3, shifted the weakly and moderately acidic sites to high temperatures, promoted the conversion of tar and char, and inhibited the formation of CO2. The H2 yield increased to 54.6 mL/g at 5% Fe/Ca catalyst. The addition of Ni to Fe/Ca improved the catalyst dispersion and promoted the adsorption of alkaline sites, while Ni formed a stable Fe3Ni2 alloy with Fe. The yields of H2 and CO increased from 54.6 mL/g and 63.4 mL/g (0.5% Fe/Ca) to 95.5 mL/g and 70.0 mL/g (0.5% Ni–Fe/Ca), respectively. The CO2 generation was suppressed at high temperatures and the calorific value of pyrolysis gas was significantly increased. Moreover, the acid wash pretreatment improved the tar yield, the alkaline sites in the Ni–Fe/Ca catalyst contributed to the conversion of aromatics and the reforming of CO2, and the presence of AAEMs promoted the redox reaction between gas and solid. The increase in the heating rate (100 °C/min) was beneficial to improve the activity of the Ni–Fe/Ca catalyst. The yields of H2 and CO reached 121.7 mL/g and 71.9 mL/g, respectively.

Conversion of Waste Corn Straw to Value-Added Fuel via Hydrothermal Carbonization after Acid Washing

To enhance the hydrothermal carbonization (HTC) process on biomass waste and improve the quality of biomass solid fuel. Corn straw was pretreated with acid washing and subsequently hydrothermally carbonized at 180–270 °C. The solid product obtained (hydrochars) was compared with the solid product produced from untreated hydrothermally carbonized straw. The results show that the acid pretreatment removed 7.9% of the ash from the straw. ICP and XRD analysis show that most of the alkali and alkaline earth metals have been removed. This addresses the defect of high ash content as the HTC temperature increases. The HHV of hydrochars produced by HTC after acid washing can reach 27.7 MJ/kg, which is nearly 10% higher than that of hydrochars prepared without acid washing pretreatment, and nearly 70% higher than that of straw raw materials. Elemental analysis and FTIR analysis show that the acid washing pretreatment changed the content and structure of the biomass components in the straw, resulting in a more complete HTC reaction and higher carbon sequestration. The decrease of H/C and O/C deepened the degree of coal-like transformation of hydrochars, with the lowest approaching the bituminous coal zone. The combustion characteristics of the hydrochars prepared after acid washing were significantly upgraded, the comprehensive combustion index and thermal stability of hydrochars both increased. Therefore, HTC after acid washing pretreatment is beneficial to further improve the high heating value and combustion characteristics of hydrochar.

Surface Pretreatments of AA5083 Aluminum Alloy with Enhanced Corrosion Protection for Cerium-Based Conversion Coatings Application: Combined Experimental and Computational Analysis.

The effects of surface pretreatments on the cerium-based conversion coating applied on an AA5083 aluminum alloy were investigated using a combination of scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), polarization testing, and electrochemical impedance spectroscopy. Two steps of pretreatments containing acidic or alkaline solutions were applied to the surface to study the effects of surface pretreatments. Among the pretreated samples, the sample prepared by the pretreatment of the alkaline solution then acid washing presented higher corrosion protection (~3 orders of magnitude higher than the sample without pretreatment). This pretreatment provided a more active surface for the deposition of the cerium layer and provided a more suitable substrate for film formation, and made a more uniform film. The surface morphology of samples confirmed that the best surface coverage was presented by alkaline solution then acid washing pretreatment. The presence of cerium in the (EDS) analysis demonstrated that pretreatment with the alkaline solution then acid washing resulted in a higher deposition of the cerium layer on the aluminum surface. After selecting the best surface pretreatment, various deposition times of cerium baths were investigated. The best deposition time was achieved at 10 min, and after this critical time, a cracked film formed on the surface that could not be protective. The corrosion resistance of cerium-based conversion coatings obtained by electrochemical tests were used for training three computational techniques (artificial neural network (ANN), adaptive neuro-fuzzy inference system (ANFIS), and support vector machine regression (SVMR)) based on Pretreatment-1 (acidic or alkaline cleaning: pH (1)), Pretreatment-2 (acidic or alkaline cleaning: pH (2)), and deposition time in the cerium bath as an input. Various statistical criteria showed that the ANFIS model (R2 = 0.99, MSE = 48.83, and MAE = 3.49) could forecast the corrosion behavior of a cerium-based conversion coating more accurately than other models. Finally, due to the robust performance of ANFIS in modeling, the effect of each parameter was studied.

Synthesis of waste bagasse-derived Li4SiO4-based ceramics for cyclic CO2 capture: Investigation on the effects of different pretreatment approaches

The bagasse, which is a typical agricultural and forestry waste, was employed as the silicon source to produce Li4SiO4-based ceramics with superior CO2 sorption performance. It is found that the presence of impurities elements in the bagasse ash will bring complex side reactions and form side products during the sorbent preparation process, which are extremely harmful to the performance of the synthetic sorbent. Pretreatment has been considered as an effective approach to reduce the impurities elements. In this work, the effects and mechanisms of water/acid washing pretreatments on bagasse ash were firstly detailed investigate and compared. The results indicate that the hydrochloric acid washing pretreatment can effectively remove the residual metals (Ca, Fe, etc.) in the sample in addition to the water-soluble impurities (K, P, S, etc.). The maximum sorption capacity of sorbent synthesized by the acid washing pretreatment is about 0.32 g/g sorbent and the superior performance can be well maintained over 10 cycles. A novel technical route utilizing the ash from biomass power plants for in-situ CO2 capture has been developed, which has great potential for carbon capture in the future.

Effect of alkali and alkaline metals on gas formation behavior and kinetics during pyrolysis of pine wood

This study examines the acid and alkaline treatment of pine wood to help understand the effect of alkali and alkaline earth metals (AAEMs) content on the pyrolysis behavior at different temperatures. Acid and alkali pretreatment of pine wood were conducted to modify AAEMs content by ion-exchanging method. Thermal kinetic behavior of the pretreated samples was first conducted by a thermogravimetric analyzer (TGA) at different heating rates that provided activation energies of pyrolysis. Gas formation behavior of the samples for different extents of conversion was carried out in a fixed-bed reactor at two different temperatures of 823 K and 1073 K. Evolutionary behavior of the gas components during pyrolysis, including flow rate, and yield and their energy content were measured and compared. Results showed that the values of activation energies increased with the extent of conversion for all the pretreated samples examined. The effect of AAEMs on pyrolysis behavior of biomass varied with the extent of conversion. The presence of AAEMs in biomass decreased the decomposition energy at low conversion while it greatly improved under high conversion. Besides, alkali treated sample with higher AAEM content enhanced the gas and char yield while it reduced the bio-oil production at low temperature with low conversion. However, at high temperature the opposite trend was observed. Presence of AAEMs was favorable for the generation of H2, CO, CO2 and CnHm at low temperature, while it showed an inhibition effect on CO and CnHm yield and syngas energy at high temperature. The catalytic mechanism of AAEMs on the pyrolysis behavior at different temperatures was discussed based on activation energy and gaseous formation. Results revealed decomposition of carboxylate at low temperature and formation of stable biomass-Na (BM-Na) structure at high temperature that led to the variation of activation energy and changed gaseous products yield and syngas energy. Acid washing pretreatment was found to be effective to enhance bio-oil yield at low temperature and increase syngas energy at high temperature. Syngas yield of acid pretreated sample was 19.6% higher than that raw sample, while alkali pretreatment was favorable for enhanced char yield. These results help to achieve the desired yield of gas or solid using AAEM modification.

Investigating the influence of acid washing pretreatment and Zn/activated biochar catalyst on thermal conversion of Cladophora glomerata to value-added bio-products

The production of sustainable energy resources are of great importance in the energy industry. As a result, studies have been extremely concerned with the conversion of coastal macroalgae into bio-products mostly through thermochemical processes such as pyrolysis. This study aimed to produce high efficiency value-added bio-products through the pyrolysis of the acid-washed Cladophora glomerata (ACG). It also attempted to upgrade the bio-products through the catalytic pyrolysis with the use of Zn/Activated biochar (Zn/C) catalyst. The catalyst was prepared via the carbonization of the ZnCl2 impregnated ACG under the optimal reaction conditions and was characterized by BET, XRD, FT-IR, FESEM-EDS and ICP analyzes. The experimental results indicated that the acid washing pretreatment led to the removal of inorganic contents of the biomass, and consequently to the significant increase in the bio-oil yield. In addition to this remarkable change in the product distributions and according to the results of the catalytic experiment, the Zn/C catalyst decreased the acid and oxygen contents of the bio-oil. It also increased the aromatic contents of the bio-oil and promoted H2 production. Accordingly, it favorably upgraded the quality of the bio-oil and pyro-gas. The study concludes that Cladophora macroalgae can be widely used as both feedstock and catalyst in order to produce value-added bio-products in the energy industry.

RETRACTED: Catalytic co-pyrolysis of rice straw and ulva prolifera macroalgae: Effects of process parameter on bio-oil up-gradation

Co-pyrolysis of rice straw (RS) and ulva prolifera macroalgae (UPM) was studied over a series of nickel-iron-layered double oxides (NiFe-LDO) supported on activated bio-char catalysts. Results showed that, co-pyrolysis produced higher bio-oil yield compared to the individual pyrolysis. Maximum bio-oil yield (46.68 wt%). was found with RS/A-UPM mixture biomass at 500 °C. While RS and UPM and it mixture (RS/UPM) without acid treated UPM was showed lower bio-oil yield. The catalytic pyrolysis up-gradation decreased the bio-oil due to the coke formation. However the bio-oil quality significantly improved with using the 5%Ga/NiFe-LDO/AC catalyst. Also, improved performance with higher amount of bio-oil and lower amounts of char and gas were achieved by acid washing the macroalgae, which is due the removal of ash content or partially fragmented the macromolecule compositions. Catalytic co-pyrolysis of feedstocks also revealed that introducing NiFe-LDO nanosheets into the activated char could result in NiFe-LDO/AC catalysts of higher surface area and increased active sites to adsorb oxygenated and nitrogenated compounds. Being impregnated by 5%Ga, catalysts with improved acid sites and thereby, advanced deoxygenation and aromatization activities were achieved. This implied that the synthesized Ga/NiFe-LDO/AC could be considered as a promising catalyst for RS/A-UPM bio-oil upgrading. • High quality bio-oil by co-pyrolysis of rice straw and ulva prolifera macroalgae. • Acid washing pretreatment considered to enhance the feedstocks synergistic effects. • Highly dispersed NiFe-LDO nanosheets synthesized over obtained activated bio-char. • NiFe, AC, and Ga were used as active phase, support, and promoter. • Advanced catalysts were achieved using Ga impregnation to promote bio-oil quality.