Hydrothermal Carbonization (HTC) Of Waste Biomasses For Carbonaceous Materials Production And Their Applications

Hydrothermal carbonization technology is emerging thermochemical conversion technology to convert biomass into potential end products such as hydrochar,bio-fuel and other chemicals.Due to its environmentally friendly aspects such as marginal greenhouse gas emissions,this technology is a hot topic for many environmental experts.In this study,the HTC carbonaceous material was studied for two different applications:heavy metal Cr?VI?removal from aqueous solution and soil amendment.Existence of heavy metals on the earth's surface and disposal of industrial effluents to the environment causes severe health issues,which needs to be correctly dealt with.Adsorption of Cr?VI?was carefully studied onto the furfural residue?FR?,eucalyptus sawdust?ESD?,corn straw?CS?and corncob?CC?in a batch system.These materials were treated in the microwave-assisted HTC with water as an effective medium,and the subsequent solid material was further treated by three different low concentrations of potassium hydroxide?KOH?.Under optimum conditions?pH 2,25°C,and 2.5 g/L adsorbent dosage?,91.72%of FR?0.05?,85.53%of ESD?KOH 0.05?,75.48%of CS?KOH 0.1?and 73.04%of CC?KOH0.05?of Cr?VI?was removed at the initial concentration of 100 mg/L to achieve equilibrium condition.The effects directed that a higher adsorption capacity of Cr?VI??36.91 mg/g for FR,34.07 mg/g for ESD,30.15 mg/g for CS and 29.46 mg/g for CC?were reached by integrating microwave-assisted treatment KOH concentration.Important parameters like effect of pH,contact time,temperature and solution concentration were optimized to investigate their effectiveness.The experimental adsorption data were best fit for the Freundlich model for FR,which instantly followed the pseudo-second-order kinetics model.Investigation of thermodynamic studies demonstrated negative values.The findings of the study suggested the modified hydrochar generated from furfural residue could be considered as an alternative to high-cost adsorbents.Soil degradation issue is a key problem which is been faced throughout the world.Two waste streams of cattle manure and Eucalyptus sawdust from farming and agriculture were used as feedstock for producing soil amended biochar via hydrothermal carbonization?HTC?.A series of experiments were conducted to examine the effects of feedstock mixing ratio and catalyst?K₃PO₄?on biochar yield and their physicochemical properties.Based on the characterization of SEM and BET of biochars,soil application tests of water holding capacity?WHC?and cation exchange capacity?CEC?were carried out.Much higher biochar yields of59%-69%were obtained in HTC of two feedstocks than those from pyrolysis method.The proximate and ultimate analytic results indicated that carbon intensified matrix was formed and more balanced nutrients were formed in the biochar from co-HTC of two substrates.The hydrochars from co-HTC of cattle manure and Eucalyptus sawdust showed much better water holding capacities than those of HTC of each individual feedstock,and a maximum WHC of40.95%?P<0.05?was obtained by supplementing catalytic hydrochar from ESD:CM?1:1?,which was 78.74%higher than that of the control.In addition,catalytic hydrothermal carbonization further enhanced the cation exchange capacity,and a highest CEC of 10.4±0.13cmol/kg was achieved by the addition of ESD:CM?catalyst 1:1?,which was 143.74%higher than that of the control.These results indicated that a significant enhancement on soil application performance occurred among different feedstock and catalyst in hydrothermal carbonization reaction.These findings suggested that HTC of cattle manure and lignocellulosic biomass is a novel approach to on-site producing soil amendment-oriented biochar for sustainable agriculture.