Coconut shell-based biochars produced by an innovative thermochemical process for obtaining improved lignocellulose-based adsorbents.

The urgent need for a simple and cost-effective thermochemical process to produce biochar has prompted this study. The aim was to develop a straightforward thermochemical process under O2-limited conditions for the production of coconut-based biochar (CBB) and to assess its ability to remove methylene blue (MB) through adsorption, comparing it with CBB produced by slow pyrolysis. CBBs were obtained under different atmospheric conditions (O2-limited, muffle furnace biochar (MFB); and inert, pyrolytic reactor biochar (PRB)), at 350, 500, and 700 °C, and for 30 and 90'. MFB and PRB were characterized using FTIR, RAMAN, SEM, EDS, and XRD analyses. Adsorption tests were conducted using 1.0 g L-1 of MFB and PRB, 10 mg L-1 of MB at 25 °C for 48 h. Characterization revealed that atmospheric conditions significantly influenced the yield and structural features of the materials. PRB exhibited higher yields and larger cavities than MFB, but quite similar spectral features. Adsorption tests indicated that MFB and PRB had qt values of 33.1 and 9.2 mg g-1, respectively, which were obtained at 700 °C and 90', and 700 °C and 30', respectively. This alternative method produced an innovative and promising lignocellulose-based material with great potential to be used as a biosorbent.

Unveiling the mechanistic aspects of methylene blue adsorption onto a novel phosphate-decorated coconut fiber lignin.

The aim of this work was to evaluate the adsorptive performance of the phosphorylated coconut fiber lignin (PCFL) obtained through an innovative biorefinery process for removing methylene blue (MB). PCFL was obtained using coconut fiber mixed with 85 % wt. H3PO4 at 70 °C for 1 h. Milled wood lignin (MWL) and PCFL were characterized by FTIR, CP-MAS 31P NMR, phosphorous and hydroxyl contents, pHPZC, and BET analyses. The batch adsorption tests evaluated the effects of the biosorbent (0.25 - 4 g L-1) and adsorbate dosages (2.5 - 7.5 mg L-1), contact time (0 - 60 min), pH (4 - 8), ionic strength (0.001 - 0.1 mol L-1) and temperature (298.15 - 318.15 K) on MB adsorption. Kinetic, equilibrium, and thermodynamic modeling were used. The phosphorous content on PCFL was 2.5 times higher than that of MWL. PCFL presented an enhanced adsorptive performance for removing MB, which was spontaneous (ΔG0 < 0), endothermic (ΔH0 > 0), with affinity between the biosorbent and adsorbate (ΔS0 > 0), and driven by physisorption (Ea > 40 kJ mol-1). The adsorptive performance of PCFL was enhanced due to the grafting of new active sites by using an innovative biorefinery process, showing its potential to be used for textile effluent remediation.

Development of a phosphorous-based biorefinery process for producing lignocellulosic functional materials from coconut wastes.

This work aimed to develop a phosphorous-based biorefinery process for obtaining phosphorylated lignocellulosic fractions in a one-pot protocol from coconut fiber. Natural coconut fiber (NCF) was mixed with 85 % m/m H3PO4 at 70 °C for 1 h to yield the modified coconut fiber (MCF), aqueous phase (AP), and coconut fiber lignin (CFL). MCF was characterized by its TAPPI, FTIR, SEM, EDX, TGA, WCA, and P content. AP was characterized regarding its pH, conductivity, glucose, furfural, HMF, total sugars and ASL contents. CFL structure was evaluated by FTIR, 1H, 31P and 1H-13C HSQC NMR, TGA and P content and was compared to that of milled wood lignin (MWL). It was observed that MCF and CFL were phosphorylated during the pulping (0.54 and 0.23 % wt., respectively), while AP has shown high sugar levels, low inhibitor content, and some remaining phosphorous. The phosphorylation of MCF and CFL also showed an enhancement of their thermal and thermo-oxidative properties. The results show that a platform of functional materials such as biosorbents, biofuels, flame retardants, and biocomposites can be created through an eco-friendly, simple, fast, and novel biorefinery process.

Elucidating the adsorption mechanism of Rhodamine B on mesoporous coconut coir-based biosorbents through a non-linear modeling and recycling approach.

The search for renewable adsorbent materials has increased continuously, being the agro-wastes an interesting alternative. This work aimed to elucidate the mechanism of adsorption of Rhodamine B on crude and modified coconut fibers from aqueous systems and the feasibility of reusing the biosorbents. The chemical modification of crude coconut fiber was carried out by the organosolv process. The biosorbents were characterized by lignocellulosic composition, FTIR, TGA, WCA, SEM, nitrogen adsorption/desorption (BET-BJH), and pH of zero point of charge (pHPZC) analyses. The batch adsorption tests evaluated the effects of the adsorbent and adsorbate dosages, contact time, and temperature on Rhodamine B adsorption. For elucidating the adsorption mechanisms involved in the process, the non-linear forms of kinetic and isotherm models were used. The regeneration of the biosorbents was evaluated by carrying out the desorption experiments. Modified coconut fiber had an increase in the amount of α-cellulose, which influenced its structural, morphological, surface, and porous properties. The removal efficiency of Rhodamine B was about 90% for modified coconut fiber and 36% for crude coconut fiber. The dye adsorption was spontaneous and endothermic for both biosorbents, showing higher spontaneity and affinity with the adsorbate for biosorbent modified. Therefore, the coconut fiber can be considered an alternative to the traditional adsorbent materials that allows the reuse by four times without performance loss, in which its adsorptive capacity has increased through its chemical modification by a biorefinery process.