P. R. Bonelli

Effect of pyrolysis temperature on composition, surface properties and thermal degradation rates of Brazil Nut shells

Changes in chemical and surface characteristics of Brazil Nut shells (Bertholletia excelsa) due to pyrolysis at different temperatures (350 degrees C, 600 degrees C, 850 degrees C) were examined. For this purpose, proximate and ultimate analyses, physical adsorption measurements of N2 (-196 degrees C) and CO, (25 degrees C) as well as samples visualisation by scanning electronic microscopy (SEM) were performed. Appreciable differences in the residue characteristics, depending markedly on the pyrolysis temperature, were observed. Release of volatile matter led to the development of pores of different sizes. Progressive increases in micropore development with increasing pyrolysis temperature took place, whereas a maximum development of larger pores occurred at 600 degrees C. Furthermore, kinetics measurements of Brazil Nut shells pyrolysis from ambient temperature up to 900 degrees C were performed by non-isothermal thermogravimetric analysis. A model taking into account the significant changes in the residue during pyrolysis, through an increase in the activation energy with temperature and solid conversion, were found to properly fit the kinetics data over the wide range of degradation investigated.

Arundo donax cane as a precursor for activated carbons preparation by phosphoric acid activation.

Canes from Arundo donax, a herbaceous rapid-growing plant, were used as precursor for activated carbon preparation by phosphoric acid activation under a self-generated atmosphere. The influence of the carbonization temperature in the range 400-550 degrees C and of the weight ratio phosphoric acid to precursor (R = 1.5-2.5) on the developed porous structure of the resulting carbons was studied for 1 h of carbonization time. Surface properties of the activated carbons were dependent on a combined effect of the conditions employed. Carbons developed either with R = 1.5 over the range 400-500 degrees C, or with R = 2 at 500 degrees C exhibited surface areas of around 1100 m2/g, the latter conditions promoting a larger pore volume and enhanced mesoporous character. For both ratios, temperature above 500 degrees C led to reduction in porosity development. A similar effect was found for the highest ratio (R = 2.5) and 500 degrees C. The influence of carrying out the carbonization either for times shorter than 1 h or under flowing N2 was also examined at selected conditions (R = 2, 500 degrees C). Shorter times induced increase in the surface area (approximately 1300 m2/g), yielding carbons with smaller mean pore radius. Activated carbons obtained under flowing N2 possessed predominant microporous structures and larger ash contents than the samples derived in the self-generated atmosphere.

Effectiveness of Cupressus sempervirens cones as biosorbent for the removal of basic dyes from aqueous solutions in batch and dynamic modes

The feasibility of using cypress cone chips from Cupressus sempervirens as a low-cost biosorbent for the removal of two representative basic dyes, methylene blue (MB) and rhodamine B (RhB), from aqueous solutions was investigated in batch and continuous modes. Dyes biosorption was strongly dependent on the solutions pH. Sorption kinetics was determined and properly described by the pseudo-second-order rate model. Experimental equilibrium isotherms fitted the Langmuir model, showing maximum biosorption capacities of 0.62 mmol/g for MB and 0.24 mmol/g for RhB. Competitive experiments from a binary solution of the dyes demonstrated the preference of the cone chips for biosorbing MB. Very low desorption efficiencies were obtained for both dyes. Dynamic experiments showed that the breakthrough time was three times higher for MB biosorption than for RhB for the same conditions. Breakthrough curves were properly represented by a mathematical model.

Potentiality of lignin from the Kraft pulping process for removal of trace nickel from wastewater: effect of demineralisation.

An industrial raw Kraft lignin was investigated to ascertain its potential use for removal of trace Ni(II) ion from wastewater by using dilute solutions (0.34-1.7 mM) as models. The effect of demineralisation on its metal sorption ability was examined by employing acid pre-treated samples. Under fixed pre-established equilibrium conditions, the raw lignin exhibited a lower effectiveness than the demineralised one, with the latter attaining an almost complete removal of Ni(II) ions. For both lignins, sorption kinetics was properly described by a pseudo-second order rate model. Equilibrium isotherms were also determined and adequately represented by conventional two-parameter models. The higher nickel sorption capacity for the demineralised lignin compared to the raw sample was consistent with enhancements in the negative magnitude of zeta potential, sodium sorption capacity, and content of phenolic hydroxyl groups occasioned by the acid pre-treatment. Accordingly, demineralisation appears as a readily convenient strategy to improve the behaviour of industrial Kraft lignin for potential use as a biosorbent of trace nickel from polluted water.

Effect of mineral matter removal on pyrolysis of wood sawdust from an invasive species

ABSTRACT Kinetics of the pyrolysis of wood sawdust from the invasive species Parkinsonia aculeata, untreated and demineralized by a mild acid treatment, is comparatively investigated in order to examine the effect of the removal of minerals naturally present in the biomass. Non-isothermal thermogravimetric analysis from room temperature up to 500°C is applied for this purpose. Demineralization shifts the process onset and the maximum degradation rate to higher temperatures, and leads to enhance the activation energy from 56 to 60 kJ mol–1, pointing to a catalytic role of alkaline and alkaline earth metals in the biomass. Likewise, the three kinds of pyrolysis products (gas, bio-char, and bio-oil) are obtained from experiments performed in a bench-scale installation at 500°C. Yields and physicochemical characteristics of the pyrolysis products are determined. The pronounced reduction in the content of metals in the sawdust leads to increase bio-oil yield in around 10%, the specific surface area of the bio-char, from ≈ 2 to ≈ 74 m2 g–1, and the higher heating value of all the pyrolysis products.

The Potential Applications of the Bio-char Derived from the Pyrolysis of an Agro-industrial Waste. Effects of Temperature and Acid-pretreatment

Abstract The bio-char arising from slow pyrolysis of raw agricultural wastes from sugarcane (Saccharum officinarum) at two different temperatures (600 and 800°C) is characterized. According to international standards, the bio-char derived at both temperatures has potential as a solid bio-fuel for domestic use, whereas only the bio-char produced at 800°C might be employed for industrial targets. Textural characterization also points to the potential use of the latter as an inexpensive rough adsorbent or soil amender. Besides, acid-pretreatment of the wastes subjected to pyrolysis at 600°C promotes an enhanced yield of the bio-char with a well-developed porous structure. Its effectiveness in removing synthetic melanoidin from a dilute solution, as a model of molasses wastewater from the sugar industry and related factories generating environmental pollution, is comparable to that of a commercial activated carbon used for comparison.

Physico-chemical Characteristics and Pyrolysis Behavior of Klason Lignins Isolated from Agro-industrial Biomass

Klason lignins lab-isolated from two lignocellulosic biomasses emerging from the processing of agro-industrial products, Aspidosperma australe wood sawdust and Bertholletia excelsa nutshells, with different contents of lignin (27 and 57 wt%, respectively), are characterized. Characterization includes determination of ash content, elemental composition, Fourier-transform infrared spectra, and surface morphological features by scanning electronic microscopy. Pyrolysis behavior of the isolated lignins as well as of the parent biomasses from which they are extracted is comparatively examined by non-isothermal thermogravimetric analysis from room temperature up to 1000°C. The lignins exhibit different ash contents and elemental compositions, as well as noticeable differences in their pyrolytic behavior depending on the botanical origin of the bio-resource and with respect to that determined for the untreated parent biomasses. Overall, the lignin isolated from the nutshells is more resistant to degrade than the sawdust-derived lignin, likely due to a more condensed chemical structure.