Abstract
During the production of paper pulp, the waste water loaded with organic materials from pulping process is discharged. Therefore, water treatment should be performed before disposing of such effluent. The use of such effluent for production of activated carbon will be effective in omitting the wastewater treatment and in obtaining the product required in many industries. In this respect, this paper deals with evaluating the performance of activated carbons (ACs) produced from black liquors (BLs) as by-products from three pulping processes of rice straw (RS) and sugar-cane bagasse (SCB), namely: alkaline, sulfite and neutral sulfite, which are coded SP, SSP and NSP, respectively. Elemental analysis and thermal analysis (TGA and DTGA) are carried out on the BLs, while the surface area (SBET), micro-/mesoporous distribution, adsorption capacity of methylene blue (MB) and iodine (I2-value), as well as Fourier transform infrared spectra (FT-IR) and scanning electron micrograph (SEM) are studied on synthesizing ACs. The optimal pulping approach for achieving BL-based AC, with the following characteristics: specific surface area (SBET) ∼ 921 and 545 m2 g−1, MB adsorption capacity 238 and 370 mg g−1, and I2-value 928 and 1255 mg g−1 of BL-based ACs, are from neutral sulfite pulping of SCB (B-NSP) and RS (RS-NSP), respectively. These finding data are ascribed to the carbon content of BL, as well as greatest total volume (VT 0.786 and 0.701 cm3 g−1) together with decreasing the volume of micropores/total (38 and 48%) of BL-NSP-ACs. It is interesting to note that the AC provided from RS-NSP has greater adsorption capacity for I2 and MB than the AC produced from RS-pulp fibres.
Highlights
Based on environment and sustainability demands, great efforts were made by the researchers in the last decades on finding the green approaches to upgrade the industrial wastes in the& 2019 The Authors
The H/ C and O/C ratios are used to measure the degree of aromaticity [44,45], as well as the degree of delignification and hydrolysis of hemicelluloses; increasing the lignin content together with hemicelluloses in black liquors (BLs) will be accompanied by decreasing the H/C and O/C
Because SO3Na included lignin of BL-rice straw (RS)-NSP, its % C is lower than that of soda pulping. From these foregoing data, we suggested that the BL with higher % C is convenient to provide activated carbons (ACs)
Summary
Based on environment and sustainability demands, great efforts were made by the researchers in the last decades on finding the green approaches to upgrade the industrial wastes in the& 2019 The Authors. The production of paper sheets from available natural wood and 2 agricultural sources triggers interesting activities in related industries [1,2]. One of the major technical approaches for paper pulping agro-wastes is based on using the black liquor (BL) by-products. The conventional approach for the use of BL is through thermal process for recovering chemicals [3], but the recovery process, especially from alkaline pulping of rice straw (RS), is extremely difficult and it demands greatest energy [4,5]. The importance of lignin was first highlighted in 1977, via introducing salt lignosulfonate or soda lignin as a sacrificial agent [6,7,8,9], for resins, enhancing the strength of concretes, water absorption inhibitor and fluidization agents, for synthesizing chemicals (e.g. resorcinols, quinones, vanillin), paints, agricultural as controlled release of agrochemicals, dispersing and stabilizing agents for dyes and ceramic suspensions, as well as source of carbon materials [10,11,12,13,14,15,16,17,18]
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