The global pulp and paper industry has long relied on wood plants as its major source of raw materials. However, environmental concerns about tree felling and deforestation, leading to or worsening several existing environmental problems has made it necessary for the industry to find new sources of raw materials. The process of producing pulp and paper from agro wastes has shown some promise to helping solve these problems.
The chemical compositions of the raw material greatly affect the efficiency of the production process, as well as the quality of the final product.
Some of the most important characteristics of the materials are moisture content, ash content and lignin content. Moisture content control is essential in the paper making process to ensure paper quality and energy conservation. Ash content is a measure of the inorganic filler or coating content of paper, including calcium carbonate, china clay and titanium dioxide. High ash content is a disadvantage for paper properties (Fahmy et al.
, 2017). A research conducted by Akpabio and Akpakpan (2012), the use of Plantain pseudo stem wastes and screw pine leaves for making pulp and paper were examined. The raw materials were obtained from Uyo Local Government Area of Akwa Ibom state, Nigeria. Determination of moisture and ash content of the samples was carried out according to the Technical Association of the Pulp and Paper Industry (TAPPI) standard methods T 258 os 76 and T 211 os 80 respectively. In review of these conducted studies, it is evident, the importance of determining the chemical compositions and physical characteristics for any agro-waste to be used to ensure efficient pulping process.
Pulping is the process of removing separating the cellulose fibers in cellulose containing materials. This is done by removing the lignin which is the substance that binds the cellulose fibers together. For non-wood plant materials, the pulping techniques of are modified methods of those which have been used in wood pulping. The pulping techniques can be mechanical, thermal, semi chemical or fully chemical methods. The chemical methods include Kraft, sulfite, soda and organosolv pulping processes. Chemical pulping is achieved by degrading the lignin and hemicelluloses into small water soluble molecules which can be washed away from the cellulose fibers without depolymerizing the cellulose fibers (Kamoga, Byaruhanga and Kirabira, 2013)
The kraft pulping method involves treatment of pulp raw materials with a hot mixture of water, sodium hydroxide (NaOH), and sodium sulfide (Na2S) (white liquor) that breaks the bonds that link lignin, hemicellulose, and cellulose. Although this is the most efficient pulping method, it produces reduced Sulphur compounds such as Hydrogen Sulphide which are pollutants. Soda pulping is a chemical process for making wood pulp with sodium hydroxide as the cooking chemical. Aremu, Aperolola and Dabonyan, (2015) researched the suitability of Nigerian corn husk and plantain stalk for pulp and paper production. Pulping of corn husk and the plantain stalk was achieved using Soda Pulping. 200 g of the raw materials (Oven-dry weight) was loaded into a 1000 ml conical flask which was then placed in a pressure pot containing sufficient amount of water and 600 ml of 7% sodium hydroxide solution was poured into the conical flask. Pulping lasted for about 3 hours at 110oC.
In the research conducted by (Akpabio and Akpakpan, 2012), the plantain pseudo stem waste was pulped by the soda process using 10% NaOH solution. The leaves of screw pine were pulped by the kraft process using pulping liquor containing 45 g of NaOH and 60 g of Na2S per liter of water having 16% sulphidity. In each case, a laboratory digester was used and the cooking was done at 100C and one atmospheric pressure for two hours. After pulping, the pulp was washed with tap water to pH 7, mild beating defibered the sample completely. Further beating in a mortar, washing and bleaching with alkaline hydrogen peroxide solution and washing produced white pulp. The yield, the moisture content, and their paper quality were then determined in accordance with TAPPI standard methods.
Alkaline kraft pulping is the dominant chemical pulping process today, but it has some serious shortcomings including air and water pollution and high investment costs. (Schweers 1972). In recent years there has been development of several organosolv methods capable of producing pulp with properties near those of kraft pulp, in a bid to reduce or eliminate the use of kraft pulping (Dahlmann and Schroeter 1990, Sundquist and Poppius-Levlin 1992, Lora and Pye 1992, Funaoka and Abe 1989, Gottlieb et al. 1992, Young 1989). In a study conducted by (Laftah and Aizan Wan, 2014), evaluating the implementation of acetone as a pulping agent for pineapple leaves, acetone-water mixtures of concentration 1%, 3%, 5%, 7% and 10% were used. The pineapple leaves used in the study were obtained from the Malaysian Pineapple Industry Board (MPIB), Johor, Malaysia. Dried samples were soaked in acetone-water mixtures of 1%, 3%, 5%, 7% and 10% (v/v) for 3 days to study the effect of acetone concentration on paper quality. A mixture of 3% acetone was also used to investigate the effect of cooking time on paper properties at 118°C under 80 kPa pressure. T
his was studied at interval times of 3, 7, 21 and 28 days. Several tests were carried out on the paper products obtained from each variation of concentration and time. The turbidity of the spent liquor from the pulping process was determined using HACH Ratio / XR Tubidimeter. The effects of acetone concentration on the pulping was first observed by the turbidity of the spent liquor. The results obtained indicated that when the acetone concentration was below 3%, the turbidity of the liquor produced was low, indicating low amounts of lignin dissolved. When the concentration was increased to 3% (v/v), there was a dramatic increase in the turbidity, implying that a large amount of lignin was precipitated at this concentration. The graph below shows the trend of the turbidity as concentration was increased.
A chart showing the turbidity of spent liquor for varying concentrations of acetone, time of soaking and time of cooking. Higher concentrations of acetone were not effective for delignification, due to the low boiling point of acetone which is 56.2°C. The results also showed steady increase in turbidity of the spent liquor with increase in both soaking and cooking time, implying that longer soaking and cooking periods respectively result in more lignin removal.
In the research carried out by Aremu, Aperolola and Dabonyan (2015) The pulp obtained was thoroughly washed under running water to remove the residual chemicals still present. Pulp samples were thereafter oven-dried. The Pulp samples were then de-fiberized in a laboratory steel blender for 5 mins and the screening was done by sieving through a screen. Paper sheets were produced from the bleached pulp using a handmade paper mould and deckle. The paper mould with the fibres was then air dried for about 3 hours in an oven. After drying, the paper samples were then pressed with an electric hot iron to improve the smoothness of the paper.