Pulping technologies can be synthesized with fiber loading with simultaneous alkaline peroxide bleaching to produce lightweight high-opacity printing papers. We compared the results of recent experiments on combining oxalic acid pretreated wood chips used for thermomechanical pulp (TMP) with fiber loading and previous experiments on combining similar pulps treated with fungal and microwave pretreatments with fiber loading. For TMP at 100 mL CSF, various species and pretreatments resulted in differences in (a) energy requirements for pulp production, (b) properties of handsheets prepared from pulps, and (c) response of pulps to precipitated calcium carbonate added conventionally and by fiber loading. Of the three treatment methods (oxalic acid, fungal (bio-treatment), and microwave), refining energy reduction was greatest for bio-treated TMP (31%). For microwave and oxalic acid treated pulps, energy was reduced 10% and 20%, respectively. All three pretreatments improved handsheet strength properties to about the same extent. Brightness and scattering coefficient were reduced the least by oxalic acid treatment, followed by microwave and bio-pretreatments. Fiber loading of bio-pretreated TMP improved handsheet strength compared with that of control TMP. Fiber loading and direct loading of oxalic acid pretreated pulps resulted in similar handsheet strengths.
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