Study On Synthesis Of High-Purity Monoalkyl Phosphate And Its Application On Deinking

Wastepaper recycling as an effective way for sustainable paper industry developmentembodys the principle of cycle economy. Clean production and sustainable development alsorequire wastepaper deinking process and corresponding agents be low energy-consuming,efficient and environment-friendly as a main process of wastepaper recycling. Traditionaldeinking technology and agents can not meet these requirments. Alkyl phosphate is a widelyused surfactant with good performance such as excellent dispersancy, biodegradation and goodfoam characteristics of its alkali metal salt. So monoalkyl phosphate is a high-performanceenvironment-friendly deinking surfactant which can be used in washing-flotation deinkingtechnology.In traditional technology, monoalkyl phosphate content is generally between 60-90% andresidual phosphoric acid is between 4-10% in the product, which prevent its further research ondeinking. So developing a new technology by which we can get high-purity monoalkylphosphate with low content of residual phosphoric acid or alcohol is very significant not only inits application, but also in academy.This dissertation aims to produce high-purity monoalkyl phosphate and further research onits application. Firstly, a traditional technology-phosphorus pentoxide method has beenoptimized by orthogonal design testing and single factorial design testing in which monoalkylphosphate content is 50.3%. By studying on reaction mechanism, macro-kinetic model has beenestablished theoretically, and examined to be second-order reaction experimentally, reactionkinetic model is: dc╱dt=864(min^-1)exp[-4.28×10⁴(J·mol^-1)/(RT)]c_Ac_BThen, a series of approaches have been carried out to transform former technologyincluding change in the way of adding material, adding water before reaction, hydrolysis ofbyproduct and dual-solvent extraction. Results indicate that monoalkyl phosphate content in theproduct can reach 96.7%, residual phosphoric acid content is 0.4%. Further, based on analysis of the difficulty in synthesis of high-purity monoalkyl bypolyphosphoricacid technology, high polymerization degree cyclic polyphosphoricacid as anew-style phosphorylation agent has been synthesized, and corresponding technology to producepure monoalkyl phosphate with low residual phosphoric acid, alcohol, and dialkyl phosphatesimultaneously has been developed. By uniform design testing, this technology has beenoptimized. Monoalkyl phosphate content is 98.8%, and residual phosphoric acid is less than1.0% under optimal conditions.Relationships between basic surface physicochemical properties including surface tension,cloud point, water number, permeability, contact angle of alkyl phosphate surfactant and itsmonoalkyl phosphate content have been investigated. Results indicate that monoalkyl phosphatecan decrease the surface tension more remarkably than dialkyl phosphate. The more monoalkylphosphate, the lower surface tension product has. It is also found that monoalkyl phosphate hashigher water-solubility, permeability, dispersancy and wetting power than dialkyl phosphate. Inthe alkaline solution, monoalkyl phosphate salt has good foaming and foam stability.At Last, using brightness as the evaluation index, effects of technology condition andapplication performance of high purity monoalkyl phosphate on washing-flotation deinking ofwastepaper have been studied. The experimental results indicate the optimal deinking conditionsof monoalkyl phosphat are as follows: pulping time=30 min, soaking time=40 min, deinkingtemperature=60℃, deinking time=2h, hydrogen peroxide dosage=10mL (based on 150gwastepaper, for the same as follows), EDTA dosage=1.5g, hydrogen peroxide dosage=4.5g,sodium silicate dosage=15g, deinking agent dosage=20mL.Under these optimized deinkingconditions, brightness of pulp has increased from 26.34% to 58.94%, which indicate deinkingefficiency of monoalkyl phosphate is better than commercial deinking agent and other domesticresearched products. By biomicroscopic picture, the deinking mechanism has been discussed anddeinking efficiency further assessed. Physical strength of pulp has been studied on finally withresult that high purity monoalkyl phosphate has little damage to fiber in washing-flotationdeinking process.