Sekedar Menyapa

Haii kawan lama.. sudah berapa lama ya aku tidak menyapa kalian semua. Berharap kabar baik selalu ada pada kalian. Amiin...Apa cerita kalian yang paling mengesankan hari ini? pasti semua punya cerita. Haa.. meskipun kalian sedih atau bahagia, mudah-mudahan itulah rencana terbaik yang Allah beri pada kalian hari ini. Bagaimanakah jalan ceritanya? lancarkah?  gagalkah? baikkah? burukkah? Semua itu ada "skenario"-Nya sendiri yang telah ditetapkan. Tidak usah terlalu pesimis  jika tidak sesuai dengan harapanmu. Dan pastinyaa... akan ada masa dimana kegagalanmu saat ini akan tergantikan dengan kebahagiaan yang tiada tara. Trust me, Believe it !. Syukurlah jika ceritamu hari ini membuatmu sangat bahagia. Jangan lupa.. Give Thanks to Allah and say Alhamdulillah. Keberhasilan maupun kegagalan saat ini jangan sampai membuatmu terlena. Aku tahu di dalam diri kalian masing-masing pasti terdapat ketegaran jiwa. Manfaatkan itu, karena itulah yang akan membuatmu tetap kuat setegar karang di lautan. Boleh sih punya rasa kecewa, tapi hilangkanlah secepat mungkin. karena jika tidak, hal itu akan membuatmu semakin terpuruk. Bahkan, kalian bisa menangis kok, jika bisa sedikit menenangkan jiwa. Kejadian hari ini, biarkan menjadi hari ini. Besok sudah lain lagi ceritanya. Aku tidak mau kalian ketinggalan cerita besok, kalau kalian tidak mau bangkit dari keterpurukan hari ini. Let's move up friends !! :D

My English Essay

The important of bleaching process in pulp making process

As we know that everybody  all over the world needs paper for their daily life. Paper is used in every part of human’s life such as for writing, packaging materials, tissues, printing, and many more. The raw material for making paper is wood. Then, woods are processed to be pulp. After that, pulp is processed in paper machine to form it become a paper. Do you know about the pulp making process? There are five main stages in pulp making process. They are debarking, cooking, washing, screening, and bleaching. This five stages are very important to do,  so that we can produce the good quality of pulp. Bleaching is one of the important stage in pulping process. Bleaching is the process that  removing all of the lignin that still remains after cooking process, as the lignin contains the chromophoric groups which make the pulp dark . Although bleaching is important process, it’s using is optional. Why? Here is the reason. Pulp produced by the Kraft process is brown.  This presents no problem for certain uses, for example sack paper, most corrugated boxes, some bag paper, and etc.  However, a major proportion of the Kraft pulp that is made is used for white or colored papers such as writing and printing papers, so the pulp needs to be bleached.

Strictly speaking, bleaching and cooking are both delignification processes, and modern developments have tended to blur the difference between the two processes.  However, traditionally the name 'bleaching' is reserved for delignification that is taking place downstream of the cooking process.  In practice, there are two separate "bleaching" process steps: oxygen delignification and final bleaching.  Oxygen delignification removes about half of the lignin remaining after the cooking process, while the final bleaching removes all remaining lignin.

The first step in bleaching process is oxygen delignification. In oxygen delignification, washed pulp is treated with a highly alkaline solution of sodium hydroxide.  The high pH ionizes phenolic groups in the lignin, which are then attacked by molecular oxygen.  The aromatic part of the lignin is partly destroyed and it is then depolymerized to lower molecular weight compounds.  These are more soluble in water and can be removed from the fibers.  It is important that the pulp has been at least partly washed beforehand because the black liquor solids in unwashed pulp consume oxygen.  After the oxygen delignification stage, the pulp has to be washed very well.

The final bleaching is always carried out in several stages to improve the efficiency of the chemicals used, and to decrease the strength loss of the pulp.  There are quite a number of bleaching chemicals used commercially, and many more have been tried in the laboratory. The chemicals used are:  chlorine, chlorine dioxide, sodium hypochlorite, oxygen, hydrogen peroxide, and  ozone. Of these chemicals, the first three contain chlorine atoms, while the last three use non-chlorine oxidizing compounds.  Elemental chlorine is efficient in bleaching the pulp and does not degrade the pulp strength.  However, it produces a large amount of chlorinated organic compounds in the effluent.

Essentially, the objective of bleaching are to remove lignin, maintain cellulose chain length, and brighten the fibers. First is remove lignin. It means that the lignin that have brown color must be throwed away, so it will make the color of paper brighter, not as dark as before. Bleaching agents are said to be “selective“ if they readily remove lignin without substantially attacking the cellulose. Beside that, the existence of lignin can make a degradation to the paper, so it will influence the strength of paper. Second is to maintain cellulose chain length , it means that the pulp will have more strength and can stabilize the bonding between the cellulose molecule. The third is to brighten the fibers. In this case, we can choose whether we will use once or more than one bleaching to get the brightness that suitable with the paper product that will be produced.

Three aspects are important for monitoring the various steps in the bleaching process. They are kappa number, viscosity, and brightness. The first is kappa number. Kappa is a number that measures the amount of lignin remaining in a pulp sample. Beside kappa number, there is viscosity that indicates the cellulose chain length. And the last is brightness that monitors how well color bodies are being removed from the pulp.

From the explanation above, we can conclude that  the using of bleaching process is actually optional. But, the paper which is have been bleached have better quality and stronger than the paper which is not have been bleached before. So, we can choose whether will using bleaching process once, more than one, or not at all. It depends on the final product that will be produced.