The enhancement of black liquor treatment by applying a natural flocculant and converting its sludge to a high‐benefit product

Abstract

Black liquor (BL) as lignocellulosic-based industrial wastewater is largely attained from a chemical pretreatment process. When treated with the commonly used coagulant polyaluminum chloride (PACl), BL was decolourized but its pH decreased drastically from 13 to 4-5. Chitosan as a natural flocculant was added to the BL treatment process to support the PACl. The combination of coagulant-flocculant (PACl-Chitosan) effectively generated sludge, rejuvenated the treated BL pH level to neutral, and decolourized and reduced several parameters required for the treated BL disposal. To establish a sustainable recycling process and enhance the BL treatment, the generated sludge as a potential source was recovered and converted to a carbonaceous adsorbent (CA) by applying a two-stage carbonization process, heat and steam carbonization, during which the temperature and time in the first stage of the heat-carbonization process differ. The first BL sludge-based CA (BLS-CA 1) is produced by employing the first stage heating at 575 8C for 180 min while the second black liquor sludge-based CA (BLS-CA 2) is produced by employing the first stage heating at 450 8C for 60 min. Both CAs were able to adsorb about 99 % methylene blue (MB) at MB concentration 100 mg/L for 16 h though they have smaller surface areas than commercially activated carbon, which is only able to adsorb about 70 % MB at the same concentration and adsorption time. This study demonstrates a potential way to reduce the emerging problem from the generated sludge through a sustainable recycling process as well as BL treatment.

Chitosan–Nanolignin Aerogel with Microneedles-Based Architecture Obtained from Spent Sulfite Liquor

“…The sulfite liquor which resulted during cellulose extraction contains sodium salts and hundreds of different organic molecules with many hydroxyl groups obtained from the thermo-chemical braking of α-O-4 and β-O-4 ether bonds between hemicellulose, syringyl, and guaiacyl monomers of lignin [1]. The energetic value of sulfite liquor is known, and thisis the main application; however, a higher degree of interest has emerged intothe separation and valorization of the diversity of biocomponents, including biodiesel, fertilizers, and adsorbents [1][2][3][4][5]. The proposed ionotropic adsorption of carbonaceous and metallic nano/micro-particles with activated chitosan [6,7], simultaneously with the separation of the two ionically interconnected nano-dispersed phases from the residual sulfite liquor, represents an innovative approach, with only a few studieshaving been conducted on this subject [3,8,9].…”

“…The energetic value of sulfite liquor is known, and thisis the main application; however, a higher degree of interest has emerged intothe separation and valorization of the diversity of biocomponents, including biodiesel, fertilizers, and adsorbents [1][2][3][4][5]. The proposed ionotropic adsorption of carbonaceous and metallic nano/micro-particles with activated chitosan [6,7], simultaneously with the separation of the two ionically interconnected nano-dispersed phases from the residual sulfite liquor, represents an innovative approach, with only a few studieshaving been conducted on this subject [3,8,9]. There are also documented studies in the literature on the adsorbent properties of chitosan for pollutants and metals in water [10,11].…”