Pulp paper making process uses a kind of chemical compounds and most of them comes in effluent, discharge by industry. Please suggest me the name of some compounds which is responsible for higher COD value.
Dear Dushyant
Pulp and paper industry is considered as one of the most polluter industry in the world.
The production process consists two main steps
1. Pulping
2. Bleaching
Pulping is the initial stage and the source of the most pollutant of this industry. In this process, wood chips as raw material are treated to remove lignin and improve fibers for paper making. Bleaching is the last step of the process, which aims to whiten and brighten the pulp.
The wastewaters generated from production processes of this industry include high concentration of chemicals such as sodium hydroxide, sodium carbonate, sodium sulfide, bisulfites, elemental chlorine or chlorine dioxide, calcium oxide, hydrochloric acid.
The major problems of the wastewaters are high organic content (20-110 kg COD/air dried ton paper), dark brown coloration, absorbable organic halide (AOX), toxic pollutants, etc.
The environmental problems of pulp and paper industry are not limited by the high water consumption. Wastewater generation, solid wastes including sludge generating from wastewater treatment plants and air emissions are other problems and effective disposal and treatment approaches are essential.
The major air emissions of the industry come from sulfite mills as recovery gurnaces and burnes, sulfur oxides (SOx), from Kraft operation as reduced sulfur gases and odor problems, from wood-chips digestion, spent liquor evaporation and bleaching as volatile organic carbons (VOCs), and from combustion process as nitrogen oxidies (NOx) and SOx. VOCs also include ketone, alcohol and solvents such as carbon disulfide methanol, acetone and chloroform.
Also gaseous pollutants are other environmental problems generated from pulp and paper industry. To minimize these pollutants, physico-chemical methods such as adsorption to activated coal filters absorption, thermal oxidation, catalytic oxidation and condensation have been widely used.
The wastewaters generated from pulping process consist various wooden compounds such as lignin, carbohydrate and extractives and the treatment of these wastewaters by biologically is difficult. Addition of them, some toxic compounds such as resin acids, unsaturated fatty acids, diterpene alcohols, juvaniones, chlorinated resin acids, and others can exist in the wastewaters subjecting to the process.
The most important reaction in the bleaching step is oxidation of chlorine and the main problem about the wastewater content is chlorinated organic compounds or AOX. During the process of paper producing, kaolin, CaCO3, talc and/or TiO2 are added to the pulp, to give the paper whiter color.Wastewater discharges for a pulp and paper mill contains solids, nutrients and dissolved organic matter such as lignin. It also contains alcohols, and chelating agents and inorganic materials like chlorates and transition metal compounds. Nutrients such as nitrogen and phosphorus can cause or exacerbate eutrophication of fresh water bodies such as lakes and rivers. Organic matter.
Also chemicals like organic fillers (starch, latex), colors, aluminum sulfate, etc. are used to make paper of different properties or making the process simpler.
Regards.,
Prem Baboo
I wan t to know about the particular compound/model compound those are more responsible for COD, they might be lignin model compounds or others. I want to prepare synthetic solution of that particular compound and his treatment.
You can use following three model compounds
1) Gallic acid,
AR Grade (3,4,5-trihydroxybenzoic acid; molecular formula: C7H6O5; molecular weight: 170 g; minimum assay: 98.0%
2) Tannin
AR Grade (gallotannic acid; molecular
formula: C76H52O46; molecular weight: 1701.23 g; minimum assay: 90.0%; supplier: Fine-Chem. Ltd)
3) Lignin - LR Grade
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