There are so many different research problems in text mining. Here are some of the topics you may develop:

Understanding text mining: A pragmatic approach

Retrieving Hierarchical Text Structure from Typeset Scientific Articles–a Prerequisite for E-Science Text Mining

Text mining on elementary forms in complex lexical structures

Hybrid clustering of text mining and bibliometrics applied to journal sets

Text mining with hybrid clustering schemes

Profiling academic research on digital games using text mining tools

Text mining and protein annotations: the construction and use of protein description sentences

Employing Text Mining for Semantic Tagging in DIAsDEM.

Web text mining on a scientific forum

Managing the acronym/expansion identification process for text-mining applications

Text mining tools: Instruments for scientific discovery

Logical text mining of software documents

Data and text mining the electronic medical record to improve care and to lower costs

Passage-based document retrieval as a tool for text mining with user s information needs

Improving text mining with controlled natural language: A case study for protein interactions

Pulse: Mining customer opinions from free text

Mining ontologies from text

An empirical study on dimensionality optimization in text mining for linguistic knowledge acquisition

The scam seeks project–text mining for financial scams on the internet

GPU-accelerated text mining

In case you would need some help, you can feel free to conact. Good luck!!!