Breakthrough of Carbon-Ash Recalcitrance in Hydrochar via Molten Carbonate:Engineering Mineral-Rich Biowaste Toward Sustainable Platform Carbon Materials

The function-led design of porous hydrochar from mineral-rich biowaste for environmental applications inevitably suffers from carbon-ash recalcitrance.However,a method to alter the original carbon skeleton with ash remains elusive and hinders the availability of hydrochar.Herein,we propose a facile strategy for breaking the rigid structure of carbon-ash coupled hydrochar using phase-tunable molten carbonates.A case system was designed in which livestock manure and NaHCO3 were used to prepare the activated hydrochar,and NH3 served as the target contaminant.Due to the redox effect,we found that organic fractions significantly advanced the melting temperature of Na2CO3 below 800℃.The Na species steadily broke the carbon-ash interaction as the thermal intensity increased and transformed inorganic constituents to facilitate ash dissolution,rebuilding the hydrochar skeleton with abundant hierarchical channels and active defect edges.The surface polarity and mesopore distribution collectively governed the five cycles NH3 adsorption attenuation process.Manure hydrochar delivered favorable potential for application with a maximum overall adsorption capacity of 100.49 mg·g^(-1).Integrated spectroscopic characterization and theoretical computations revealed that incorporating NH3 on the carbon surface could transfer electrons to chemisorbed oxygen,which promoted the oxidation of pyridine-N during adsorption.This work offers deep insight into the structure function correlation of hydrochar and inspires a more rational design of engineered hydrochar from high-ash biowaste.

Removal of Dyes in Aqueous Media with Hydrochar Base of Solid Tanneries Waste: Optimization Process and Application

The Response Surface Methodology (RSM) was used to optimise the conditions of preparation of activated hydrochar from tannery solid waste by hydrothermal carbonisation (HTC). The main factors such as residence time, moisture content and final carbonisation temperature were investigated during the optimisation of hydrochar preparation conditions. The three responses investigated are hydrochar yield, iodine and methylene blue indices. The results of experimental analyses showed that the yield of hydrochar decreases with increasing final temperature, leading to the formation of micropores inside the carbonaceous solid. The optimum conditions for preparing the following hydrochar were obtained: 83.10%, 390.44 mg∙g−1 and 259.63 mg∙g−1 respectively for the hydrochar yield, the iodine and methylene blue indices. The specific surface area of prepared hydrochar is 849.160 m2/g, SEM micrographs showed a porous heterogeneous surface and particularly, the hydrochar surface also revealed external pores on the hydrochar surface which acted as a pathway to the micropores. Fourier transform infrared (FTIR), however, showed a predominance of acid functions on the surface of the carbonaceous solids. Tests were carried out to eliminate indigo carmine in aqueous media. Activated hydrochar showed a high level of activity, with the Langmuir and Freundlich isotherms giving an adsorption quantity of 354.610 mol/g and a KF constant of 468.2489, respectively. The findings of the research revealed that hydrochar produced is well adapted for dyes removal.

Hydrochar Pelletization towards Solid Biofuel from Biowaste Hydrothermal Carbonization

Hydrothermal carbonization is highly applicable to high moisture biomass upgrading due to the fact that moist-ure involved can be directly used as reaction media under the subcritical-water region.With this,value-added utilization of hydrochar as solid fuel with high carbon and energy density is one of the important pathways for biomass conversion.In this review,the dewatering properties of hydrochar after the hydrothermal carbonization of biowaste,coalification degree with elemental composition and evolution,pelletization of hydrochar to enhance the mechanical properties and density,coupled with the combustion properties of hydrochar biofuel were discussed with various biomass and carbonization parameters.Potential applications for the co-combustion with coal,cleaner properties and energy balance for biowaste hydrothermal carbonization were presented as well as the challenges.

Effects of Biowaste-Derived Hydrochar on Anaerobic Digestion:Insights into Hydrochar Characteristics

Hydrochar prepared with four typical biowastes,pine wood,food waste,digested sewage sludge,and Chlorella were applied for the promotion of anaerobic digestion.The gas production and substrate composition were analyzed associated with the hydrochar characteristics.The results suggested that Chlorella hydrochar(C-C)showed the highest cumulative yield of methane(approximately 345 mL)with high total organic carbon(TOC)removal efficiency and low volatile fatty acids(VAFs)concentration.Especially,food waste hydrochar(F-C)showed a poor effect on anaerobic digestion and aroused 1.4–1.6 g/L accumulation of VAFs,in which the toxic components may account for the low efficiency.The C-C and sludge hydrochar(S-C)may develop direct interspecific electron transport(DIET)to facilitate the generation of methane by both surface groups and conductivity of the body structure,unlike pinewood hydrochar(P-C),which mainly depended on the aromatic matrix structure of hydrochar body.This work suggested that C-C can be the best candidate for the facilitation of anaerobic digestion,and N-containing biowaste like algae and lignocellulose like pine wood may establish different DIET pathways based on the physicochemical characteristics of hydrochar.

The Hydrochar Characters of Municipal Sewage Sludge Under Different Hydrothermal Temperatures and Durations

Innovative measure is a urgent requirement for managing the huge volume of municipal sewage sludge. The hydrothermal carbonation （HTC） shows some potential advantages for using hydrochar as a soil conditioner. The aim of this work was to investigate the properties of hydrochars, by means of the HTC of municipal sewage sludge under different temperatures （190 and 260~C） and reaction hours （1, 6, 12, 18 and 24 h）. The HTC led to the decreases of N, O and H contents by more than 54.6, 37.9 and 10.0%, respectively, and slight changes of C content. The Py-GC-MS analysis showed that a large proportion of fatty acids, in particular hexadecanoic acid, transferred into alkenes, olefins and aromatic compounds. The 13C-NMR and fourier transform infrared spectra （FTIR） confirmed the transformation and changes in chemical structure in which hydrochar contained lower oxygen-containing organic C of O-alkyl, carboxylic and carbonyl C and aliphaticity, but higher aromatic C and aromaticity. The rich hydrophobic functions induced in high positive charges in the charred sludge. The HTC facilitated the pore structure development, proved by higher specific surface area and specific pore volume, with a maximum of 17.30 and 0.83 cm^3 g^-1, respectively. The availabilities of N, P and K markedly reduced during HTC treatment. The activities of most heavy metals were depressed though they accumulated in the hydrochar. Further work is required to investigate the values and risk of the charred sludge amended to soil.

Bio/hydrochar Sorbents for Environmental Remediation

A rising global population and aspirational higher living standards has driven a step change in resource utilization and concomitant anthropogenic pollution across the biosphere.Low-cost and scalable technologies for environmental remediation are therefore urgently sought,with an emphasis on trash-to-treasure strategies that exploit abundant but underutilized waste by-products of existing sectors.Biochars are carbon-rich,porous solids produced by biomass pyrolysis under anaerobic or oxygen-scarce conditions at high temperature(350–700°C),while hydrochars are produced by hydrothermal biomass carbonization at lower temperature(130–250°C)and high autogenous pressures(0.3–4.0 MPa).Bio/hydrochars possess unique physicochemical properties,notably high surface areas(100–1500 m2 g-1)and porosity(0.25–2.5 cm^(3)g^(-1))and rich surface chemistry featuring carboxylic,phenolic,hydroxyl,and carbonyl functions,amenable to chemical,physical,or biochemical modification,rendering them ideal sorbents for pollutants such as heavy metals(e.g.As and Cr),and toxic organic(e.g.,dyes and xenobiotics)and inorganic(e.g.,SO_(2))molecules.Bio/hydrochars are attractive for environmental remediation of pollutant mixtures by surface complexation,redox chemistry,electrostatic interactions/ion exchange,or coprecipitation.This review discusses recent opportunities and challenges in creating bio/hydrochar sorbents and their nanocomposites through grafting,doping,and chemical/physical activation,for the depollution of aquatic and atmospheric environments.

Synergistic effects of phosphoric acid modified hydrochar and coal gangue-based zeolite on bioavailability and accumulation of cadmium and lead in contaminated soil

In this paper,a novel compound was developed by mixing H_(3)PO_(4)-modified cauliflower leaves hydrochar(CLH)and coal gangue-based Na-X zeolite(ZL).An alkaline soil contaminated with cadmium(Cd)and lead(Pb)was amended through the individual and synergistic application of CLH and ZL(1%CLH,2%CLH,1%ZL,2%ZL and 1%CLH+1%ZL),and Chinese cabbage was grown on it.Individual application of CLH was superior to ZL on decreasing the pH of alkaline soil and increasing soil available phosphorus(Olsen-P)and soil organic matter(SOM).In contrast,their combined application significantly improved the soil cation exchange capacity(CEC).Besides,the 1%CLH+1%ZL was the most efficient treatment in decreasing diethylenetriamine pentaacetate(DTPA)-extractable Cd/Pb and concentrations of these two metals in cabbage root and shoot.Their synergistic application could better increase Cd and Pb immobilization and cabbage yield than their alone application.Furthermore,the immobilization of Pb for all treatments was higher than that of Cd.The synergistic immobilization mechanism of CLH and ZL reflected that the CLH precipitated and complexed with these two metals,which may block the pores of hydrochar or wrap on the surface of hydrochar.So the continuous adsorption and complexation were prevented.Nevertheless,ZL could probably alleviate this obstacle.This finding provides helpful information about using CLH combined with ZL as a soil stabilizer to immobilize heavy metals in contaminated alkaline soil.

Experimental,Thermodynamic and Kinetic Studies for the Adsorption of Phenolic Compounds Derived from Oilfield Wastewater by the Corncob Hydrochar

The corncob hydrochar is prepared by using a stainless autoclave at 230?C for 8 h.The products are characterized by elemental analyzer,Fourier Transform infrared spectroscopy(FT-IR),X-ray diffraction(XRD)and scanning electron microscope(SEM).The effects of hydrochar dosage,pH,adsorption time and phenol concentration on the adsorption performance of hydrochar are investigated by means of single-factor experimental analysis.Based on the experiments the adsorption thermodynamic and kinetics are tentatively discussed.The results show that abundant oxygen-containing functional groups are scattered on the surface of the corncob hydrochar.The adsorption kinetics of phenol on the hydrochar corresponds well with pseudo-second-order kinetic model.Thermodynamic studies indicate that Freundlich adsorption isotherm model is much better than Langmuir model in describing the adsorption of phenol on the corncob hydrochar at 25?C-45?C.This study provides scientific basis for the development of cheap and efficient adsorbents for the removal of phenols derived from oilfield wastewater.

Selective hydrodeoxygenation of guaiacol to cyclohexanol using activated hydrochar-supported Ru catalysts

Lignin,an abundant aromatic polymer in nature,has received significant attention for its potential in the production of bio-oils and chemicals owing to increased resource availability and environmental issues.The hydrodeoxygenation of guaiacol,a lignin-derived monomer,can produce cyclohexanol,a nylon precursor,in a carbon-negative and environmentally friendly manner.This study explored the porous properties and the effects of activation methods on the Ru-based catalyst supported by environmentally friendly and cost-effective hydrochar.Highly selective cleavage of C_(ary)-O bonds was achieved under mild conditions(160°C,0.2 MPa H_(2),and 4 h),and alkali activation further improved the catalytic activity.Various characterization methods revealedthat hydrothermal treatment and alkali activation relatively contributed to the excellent performance of the catalysts and influenced their porous structure and Ru dispersion.X-ray photoelectron spectroscopy results revealed an increased formation of metallic ruthenium,indicating the effective regulation of interaction between active sites and supports.This synergistic approach used in this study,involving the valorization of cellulose-derived hydrochar and the selective production of nylon precursors from lignin-derived guaiacol,indicated the comprehensive and sustainable utilization of biomass resources.

Co-production of hydrochar and bioactive compounds from Ulva lactuca via a hydrothermal process

This study investigates the simultaneous production of hydrochar and bioactive compounds from Ulva lactuca via a hydrothermal process.The experiment was carried out using a batch reaction vessel at different reaction temperatures of 180-220◦C and various holding times of 30-90 min.As expected,both temperature and time vigorously influenced hydrochar and bioactive compound production.The maximum hydrochar yield was at 32.4 wt%.The higher heating value(HHV)of hydrochar was observed in the range of 17.68-21.07 MJ kg^(-1),near the energy content of low-rank coals.The hydrochars exhibited contact angles higher than 90°(i.e.,94-108°)for a longer time,confirming their hydrophobic surfaces.The scanning electron microscope analysis(SEM)showed that the hydrothermal process enables cracks in the spherical shape of raw U.lactuca into small and porous particles.Besides producing hydrochar,the hydrothermal process of U.lactuca also gives promising antioxidants and phenolics as bioactive compounds.The highest total phenolic content and antioxidant activity could be achieved in hydrolysate at 200℃and 30 min with the value of 1.20±0.12 mg/g and 71.6±1.3%,respectively.

A bibliographic study reviewing the last decade of hydrochar in environmental application:history,status quo,and trending research paths

Hydrothermal carbonization(HTC)technology has increasingly been considered for biomass conversion applications because of its economic and environmental advantages.As an HTC conversion product,hydrochar has been widely used in the agricultural and environmental fields for decades.A CiteSpace-based system analysis was used for conducting a bibliometric study to understand the state of hydrochar environmental application research from 2011 to 2021.Researchers had a basic understanding of hydrochar between 2011 and 2016 when they discovered hydrochar could apply to agricultural and environmental improvement projects.Keyword clustering results of the literature published in 2017-2021 showed that soil quality and plant growth were the major research topics,followed by carbon capture and greenhouse gas emissions,organic pollutant removal,and heavy metal adsorption and its bioavailability.This review also pointed out the challenge and perspective for hydrochar research and application,namely:(1)the environmental effects of hydrochar on soils need to be clarified in terms of the scope and conditions;(2)the influence of soil microorganisms needs to be investigated to illustrate the impact of hydrochar on greenhouse gas emissions;(3)combined heavy metal and organic contaminant sorption experiments for hydrochar need to be conducted for large-scale applications;(4)more research needs to be conducted to reveal the economic benefits of hydrochar and the coupling of hydrochar with anaerobic digestion technology.This review suggested that it would be valuable to create a database that contains detailed information on how hydrochar got from different sources,and different preparation conditions can be applied in the environmental field.

Co-digestion of food waste and hydrothermal liquid digestate:Promotion effect of self-generated hydrochars

Hydrothermal treatment(HTT)can efficiently valorize the digestate after anaerobic digestion.However,the disposal of the HTT liquid is challenging.This paper proposes a method to recover energy through the anaerobic co-digestion of food waste and HTT liquid fraction.The effect of HTT liquid recirculation on anaerobic co-digestion performance was investigated.This study focused on the self-generated hydrochars that remained in the HTT supernatant after centrifugation.The effect of the self-generated hydrochars on the methane(CH_(4))yield and microbial communities were discussed.After adding HTT liquids treated at 140 and 180
C,the maximum CH4 production increased to 309.36 and 331.61 mL per g COD,respectively.The HTT liquid exhibited a pH buffering effect and kept a favorable pH for the anaerobic co-digestion.In addition,the self-generated hydrochars with higher carbon content and large oxygen-containing functional groups remained in HTT liquid.They increased the electron transferring rate of the anaerobic co-digestion.The increased relative abundance of Methanosarcina,Syntrophomonadaceae,and Synergistota was observed with adding HTT liquid.The results of the principal component analysis indicate that the electron transferring rate constant had positive correlationships with the relative abundance of Methanosarcina,Syntrophomonadaceae,and Synergistota.This study can provide a good reference for the disposal of the HTT liquid and a novel insight regarding the mechanism for the anaerobic co-digestion.

Two-step hydrothermal conversion of biomass waste to humic acid using hydrochar as intermediate

Converting biomass materials to humic acid is a sustainable method for humic acid production and achieve biomass valorization. A two-step hydrothermal treatment method was adopted in this study to produce humic acid from corn stalks. In the first step of the process, hydrochar was prepared at different hydrothermal temperatures and pH values. Their chemical properties were then analyzed, and the hydrochar-derived humic acids were produced under alkaline hydrothermal conditions (denoted as HHAalk). The hydrochar, prepared under high temperature (200 °C) and strong acidic (pH 0) conditions, achieved high HHAalk yields (i.e., 67.9 wt% and 68.8 wt% calculated based on weight of hydrochar). The sources of HHAalk formation were as follows: 1) production in the hydrochar preparation stage, and 2) increment under the alkaline hydrothermal treatment of hydrochar. The degree of hydrochar unsaturation was suggested as an indicator for evaluating the hydrochar humification potential under alkaline hydrothermal conditions. This study provides an important reference for the preparation of suitable hydrochar with high hydrothermal humification potential.

ASSESSMENT OF HEAVY METALS IN HYDROCHAR PRODUCED BY HYDROTHERMAL CARBONIZATION OF DAIRY MANURE

Hydrochar produced from dairy manure is a regulated biosolid if being promoted for agricultural applications thus must have the properties that comply with all environmental standards and government regulations,including the levels of heavy metals(HMs).In this study,systematic research was conducted on HM levels in hydrochar from dairy manure and on the effects of processing conditions,including processing temperature(180–255℃),holding time(30–120 min)and solid content of manure slurry(2%–15%),through a central composite design and statistical analyses.It was found that HMs can be retained in hydrochar,ranging from 40%to 100%.The processing temperature and solid content in the feed were the most influential process parameters that affected HMs retention in hydrochar.Statistical analysis showed that there was no single optimal point to minimize HMs retained in hydrochar,but there were minimization points at given processing time and solid content.Most HMs concentrations were higher in hydrochar than those initially in dairy manure but were greatly below the thresholds as set by the US government regulations.Thus,hydrochar is feasible for use as a phosphorus-enriched organic fertilizer and/or soil amendment for agricultural applications without serious concerns about HMs it might contain.

Rice Husk at a Glance:From Agro-Industrial to Modern Applications

Excessive waste production has led to the concept of a circular bioeconomy to deliver valuable by-products and improve environmental sustainability.The annual worldwide rice production accounts for more than 750 million tons of grain and 150 million tons of husk.Rice husk(RH)contains valuable biomaterials with extensive applications in various fields.The proportions of each component depend primarily on rice genotype,soil chemistry,and climatic conditions.RH and its derivatives,including ash,biochar,hydrochar,and activated carbon have been placed foreground of applications in agriculture and other industries.While the investigation on RH’s compositions,microstructures,and by-products has been done copiously,owing to its unique features,it is still an open-ended area with enormous scope for innovation,research,and technology.Here,we reviewed the latest applications of RH and its derivatives,including fuel and other energy resources,construction materials,pharmacy,medicine,and nanobiotechnology to keep this versatile biomaterial in the spotlight.

吸附法处理含吡啶废水的试验研究

利用水热碳化技术制备了一种莲房基水热炭。通过产物表征､正交实验､吸附等温线､吸附动力学､再生实验等探讨了水热炭在含吡啶废水处理中的应用。结果表明,莲房水热炭具有不同尺寸的孔隙结构,其表面分布着较为丰富的含氧官能团;水热炭吸附吡啶过程中各因素影响顺序为:吡啶初始浓度>水热炭投加量>溶液pH>吸附时间;莲房水热炭对吡啶的吸附动力学符合准二级模型,在35℃与45℃时Freundlich模型可较好地描述吸附等温线规律;25℃时莲房水热炭对吡啶的最大吸附量为31.28 mg/g;磷酸溶液对莲房水热炭的再生效果优于NaOH溶液;莲房水热炭经6次再生后,对吡啶仍具较好的吸附能力。

玉米秸秆水热生物炭施用对土壤重金属Cd生物有效性和微生物群落的影响

为了探究玉米秸秆水热生物炭(简称水热炭)施用对镉(Cd)污染土壤的修复效果及作用机制,通过盆栽试验,分析了不同水热炭在不同添加率下(1%和3%)对土壤Cd生物有效性和作物吸收的影响,并探究了不同条件下的微生物群落结构。结果表明:与对照相比,水热炭施用显著提高了土壤有机质和溶解性有机碳含量,土壤中二乙烯三胺五乙酸提取的Cd(DTPA-Cd)和油菜叶片Cd含量分别降低了5.01%~20.98%和10.82%~34.16%。提高水热温度和水热炭添加率有助于降低土壤DTPA-Cd含量。此外,施用水热炭显著增强了根际土壤细菌的多样性和丰度,且明显改变了微生物群落结构。与对照组相比,施用水热炭显著降低了根际土壤中Actinobacteriota的相对丰度,提高了Proteobacteria和Bacteroidota的相对丰度。冗余分析表明土壤溶解性有机碳含量是影响根际土壤细菌群落结构的关键因素。因此,水热炭对重金属污染土壤有很大的修复潜力,但其对土壤重金属的长期效应有待进一步研究。

两种铁改性水热炭对土壤中铬固化效能及其形态影响

本实验采用机械球磨法分别制备零价铁(ZVI)、黄铁矿负载水热炭,通过土壤提取实验和土柱淋溶实验,对比添加不同材料后土壤中铬(Cr)含量的变化,分析淋溶液中Cr累积释放规律及Cr在土柱中的纵向迁移行为.实验结果表明,与其他材料相比,施加ZVI改性水热炭(ZBC)和黄铁矿改性水热炭(HBC)对土壤中Cr均有优秀的固化效果.在低投加量(5 g·kg^(-1))下ZBC、HBC使土壤浸出液中总铬浓度分别降低35.8%、39.6%,而土壤中有效铁含量涨幅均小于0.1%,解决了使用ZVI和黄铁矿引起的土壤铁含量过度增加的问题.在土柱淋溶实验中,施加ZBC、HBC后淋溶液总铬含量较CK(未加改性水热炭的对照组)分别下降27.3%、39.3%;土柱下部未污染土壤总铬含量分别降低31.4%、56.3%,Cr(Ⅵ)浓度分别降低51.7%、44.4%.结合表征可得,土壤中的Cr可被ZBC、HBC吸附,水热炭负载的Fe可将Cr(Ⅵ)还原成Cr(Ⅲ)并附着在土壤中,HBC中的FeS_(2)有效参与了对Cr(Ⅵ)的还原.总的来看,HBC对土壤中Cr的固化效果更好,可为水热炭修复重金属污染土壤的应用提供思路与探索.

壳聚糖改性污泥水热炭活化过硫酸盐降解活性黑5染料废水

印染废水可生化性低,生物处理难度大.通过在剩余污泥中掺杂壳聚糖,经水热处理制备出壳聚糖改性生物炭(CBC),并用于活化过二硫酸盐(PDS),实现对活性黑5(RB5)染料废水的高效降解.在水热温度为200℃,水热时间为6 h时制备的CBC对RB5的去除效果最优,反应60 min去除率可达到100%.此外,PDS投量为2 mmol·L^(−1),CBC投量为5 g·L^(−1),初始pH=5时反应效果最佳.反应系统中的Cl^(-)和NO_(3)^(-)对RB5去除几乎无影响,而PO_(4)^(3-)、HCO_(3)^(-)有明显抑制作用.机理研究证实了单线态氧(^(1)O_(2))对RB5的降解起主要贡献,而不是PDS氧化体系常见的硫酸根自由基.

废弃生物质水热炭化衍生碳基光催化材料的研究进展

水热炭化是一种经济且环境友好的废弃生物质热化学转化技术.废弃生物质通过水热炭化制备碳基光催化材料,不仅可实现废弃物的高值利用,而且可通过光催化材料的的应用缓解环境污染和能源危机.本综述将水热炭化制备的废弃生物质碳基光催化材料分成水热炭、碳点和碳基复合材料三类,并系统总结其制备、光催化机理和应用方面的研究进展.首先,归纳了3种光催化剂的制备,包括形成机理和物化结构;然后分别阐述了各类催化剂的光催化过程和光催化性能提高途径,以及从有机污染物降解、重金属去除、消毒、产氢和CO_(2)还原等领域介绍了光催化应用;最后,对该领域未来的研究重点和发展方向进行了展望.