(219f) Characterization of Sludge From Combined Deinking Technology

Recycled fiber has become an important source for the production of the paper. In the early 70’s decades, only 7% of waste paper was used as a raw material for the production of the paper which is now increased to the 47% and acting as a major raw material for paper industry. It is possible due to improved recycling system of wastepaper. Presently all grades of paper are being recycled by various organization. Infact share of mixed office waste (MOW) in the recovered wastepaper has increased at very rapid rate during last decade.

Deinking sludge is the sludge which generates during the deinking process was mainly used for removal of paper ink. The other material such as non-cellulose material of fiber, dyes, adhesives, and fillers such as calcium carbonate and clay were also removed. All these materials are collected into the waste product called the deinking sludge. Heavy metal, polychlorinated biphenyls (PCBs) and dioxin are the main constituents of Deinking sludge. Therefore, sludge disposal is one of the most important tasks for environmental protection. In recent years, deinking mills have striven to put their sludge by products to positive use. The detail characterization of deinking sludge provides important information for the proper treatment of sludge disposal. However, the characteristics of sludge produced by the mill depend on the type of the wastepaper and deinking process.

Non-contact printed papers which include photocopier printed paper are difficult to deink using conventional methods. Toner contains synthetic binder based on polyester or copolymers of styrene with acrylates, methacrylates or butadiene. Conventional pulping with chemicals does not effectively remove the cured toner from the fiber slurry because toners have polymerized and fused onto the fibers. Toners are more difficult to disperse than conventional oil- based inks and remains as flat, rigid particles. It separates poorly from fibers during flotation and washing stages. The low removal efficiency of toners could be due to the toner remaining attached to fiber surfaces, to the physical properties of the comparatively large- sized toner particles, or to some combination of these and other factor. For these reasons conventional deinking process cannot get high efficiency to photocopier printed paper and has threatened environment badly. The use of bio-deinking technology opened up a new way for paper technology. Besides bio-deinking technology, ultrasonic and UV-irradiation technologies have begun to be investigated by some researchers, which is still in its evolutionary stage. The combined deinking technology i.e. the combination of Chemical, Ultrasonic, UV-irradiation and Enzymatic methods were introduced very recently in to the deinking process of photocopier printed paper. The paper presents the prospects for utilization of the sludge produced from combined deinking of photocopier paper at laboratory scale and more specifically focuses on characterisation of the produced sludge and evaluation of the prospects of sludge utilization on the basis of the above characteristics. Deinking experiments were conducted by utilizing  various deinking technologies namely (i) Chemical deinking (ii) Enzymatic deinking (ii) Combined (chemical and enzyme deinking ) (iv) Combined (chemical, enzyme, Ultrasound and UV –irradiation) in the laboratory. The by- product sludge was collected and yield was calculated. Further detailed characterisation was carried out to find out moisture content, pH, ultimate and proximate analysis, ash content, inorganic/ organic matter, electrical conductivity, and heavy metal.  For studying the mineralogy of the deinking sludge XRD patters have been recorded in the 2ɵ range of 5º-100º. Thermogravimeteric and differential thermal analysis (TG-DTA) has been carried out to determine the thermal stability. From TGA the reaction kinetics of drying, Pyrolysis and combustion of deinking sludge were studied. Scanning electron micrograph photographs has been used for image analysis. Characterization of effluent is presented in term of BOD: COD ratio of the effluent.